[v4,1/6] libcamera: controls: Update the ColourTemperature control to be writable

20894 diff mbox series

For manual control it is helpful to be able to specify a fixed colour
temperature. It also provides an easy way to apply the temperature
specific CCMs and colour gains that are contained in the tuning files.

Document this and update the control dependencies.

Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com>
---
 src/libcamera/control_ids_core.yaml | 24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

On Tue, Aug 13, 2024 at 10:44:18AM +0200, Stefan Klug wrote:
> For manual control it is helpful to be able to specify a fixed colour
> temperature. It also provides an easy way to apply the temperature
> specific CCMs and colour gains that are contained in the tuning files.
> 
> Document this and update the control dependencies.
> 
> Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com>

Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>

> ---
>  src/libcamera/control_ids_core.yaml | 24 ++++++++++++++++++++----
>  1 file changed, 20 insertions(+), 4 deletions(-)
> 
> diff --git a/src/libcamera/control_ids_core.yaml b/src/libcamera/control_ids_core.yaml
> index cf40771d3896..04dcc4af67fc 100644
> --- a/src/libcamera/control_ids_core.yaml
> +++ b/src/libcamera/control_ids_core.yaml
> @@ -252,9 +252,12 @@ controls:
>    - AwbEnable:
>        type: bool
>        description: |
> -        Enable or disable the AWB.
> +        Enable or disable the AWB. Disabling AWB stops updates to the
> +        ColourGains and to the ColourCorrectionMatrix.
>  
> +        \sa ColourCorrectionMatrix
>          \sa ColourGains
> +        \sa ColourTemperature
>  
>    # AwbMode needs further attention:
>    # - Auto-generate max enum value.
> @@ -309,13 +312,24 @@ controls:
>          disabled.
>  
>          \sa AwbEnable
> +        \sa ColourTemperature
>        size: [2]
>  
>    - ColourTemperature:
>        type: int32_t
> -      description: Report the current estimate of the colour temperature, in
> -        kelvin, for this frame. The ColourTemperature control can only be
> -        returned in metadata.
> +      description: |
> +        Report the current estimate of the colour temperature, in kelvin, for
> +        this frame. An implementation may also allow this control to be set when
> +        AWB is disabled. In that case ColourGains and the ColourCorrectionMatrix
> +        get set accordingly. If either ColourGains or ColourCorrectionMatrix are
> +        specified at the same time, they take precedence.
> +
> +        The metadata will only report measured colour temperature values when
> +        available, even if set manually.
> +
> +        \sa AwbEnable
> +        \sa ColourCorrectionMatrix
> +        \sa ColourGains
>  
>    - Saturation:
>        type: float
> @@ -365,6 +379,8 @@ controls:
>          transformation. The 3x3 matrix is stored in conventional reading
>          order in an array of 9 floating point values.
>  
> +        \sa AwbEnable
> +        \sa ColourTemperature
>        size: [3,3]
>  
>    - ScalerCrop:
> -- 
> 2.43.0
>

Hi Stefan,

Thank you for the patch.

On Tue, Aug 13, 2024 at 10:44:18AM +0200, Stefan Klug wrote:
> For manual control it is helpful to be able to specify a fixed colour
> temperature. It also provides an easy way to apply the temperature
> specific CCMs and colour gains that are contained in the tuning files.
> 
> Document this and update the control dependencies.
> 
> Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com>
> ---
>  src/libcamera/control_ids_core.yaml | 24 ++++++++++++++++++++----
>  1 file changed, 20 insertions(+), 4 deletions(-)
> 
> diff --git a/src/libcamera/control_ids_core.yaml b/src/libcamera/control_ids_core.yaml
> index cf40771d3896..04dcc4af67fc 100644
> --- a/src/libcamera/control_ids_core.yaml
> +++ b/src/libcamera/control_ids_core.yaml
> @@ -252,9 +252,12 @@ controls:
>    - AwbEnable:
>        type: bool
>        description: |
> -        Enable or disable the AWB.
> +        Enable or disable the AWB. Disabling AWB stops updates to the
> +        ColourGains and to the ColourCorrectionMatrix.

Please split this in two paragraphs. The first paragraph is translated
to a \brief doxygen command, and should be a single sentence. Same
below.

I would like to clarify this a bit. Here's an attempt, is it what you
mean ?

	Enable or disable the AWB.

	When AWB is enabled, the algorithm estimates the colour	temperature of
	the scene, and computes colour gains and the colour correction matrix
	automatically. The computed colour temperate, gains and correction
	matrix are reported in metadata. The corresponding controls are ignored
	if set in a request.

	When AWB is disabled, the colour temperature, gains and correction
	matrix are not updated automatically and can be set manually in
	requests.

>  
> +        \sa ColourCorrectionMatrix
>          \sa ColourGains
> +        \sa ColourTemperature
>  
>    # AwbMode needs further attention:
>    # - Auto-generate max enum value.
> @@ -309,13 +312,24 @@ controls:
>          disabled.
>  
>          \sa AwbEnable
> +        \sa ColourTemperature
>        size: [2]
>  
>    - ColourTemperature:
>        type: int32_t
> -      description: Report the current estimate of the colour temperature, in
> -        kelvin, for this frame. The ColourTemperature control can only be
> -        returned in metadata.
> +      description: |
> +        Report the current estimate of the colour temperature, in kelvin, for
> +        this frame. An implementation may also allow this control to be set when

s/also //

> +        AWB is disabled. In that case ColourGains and the ColourCorrectionMatrix
> +        get set accordingly. If either ColourGains or ColourCorrectionMatrix are
> +        specified at the same time, they take precedence.

maybe "they take precedence, and the ColourTemperature is ignored" ? Or,
if an application sets ColourTemperature and ColourGains but not
ColourCorrectionMatrix, do you expect the implementation to apply the
requested ColourGains and set ColourCorrectionMatrix based on the
temperature ?

> +
> +        The metadata will only report measured colour temperature values when
> +        available, even if set manually.

I'm not sure to understand this.

> +
> +        \sa AwbEnable
> +        \sa ColourCorrectionMatrix
> +        \sa ColourGains
>  
>    - Saturation:
>        type: float
> @@ -365,6 +379,8 @@ controls:
>          transformation. The 3x3 matrix is stored in conventional reading
>          order in an array of 9 floating point values.
>  
> +        \sa AwbEnable
> +        \sa ColourTemperature
>        size: [3,3]
>  
>    - ScalerCrop:

Hi Laurent,

Thank you for the review.

On Fri, Aug 30, 2024 at 02:01:19AM +0300, Laurent Pinchart wrote:
> Hi Stefan,
> 
> Thank you for the patch.
> 
> On Tue, Aug 13, 2024 at 10:44:18AM +0200, Stefan Klug wrote:
> > For manual control it is helpful to be able to specify a fixed colour
> > temperature. It also provides an easy way to apply the temperature
> > specific CCMs and colour gains that are contained in the tuning files.
> > 
> > Document this and update the control dependencies.
> > 
> > Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com>
> > ---
> >  src/libcamera/control_ids_core.yaml | 24 ++++++++++++++++++++----
> >  1 file changed, 20 insertions(+), 4 deletions(-)
> > 
> > diff --git a/src/libcamera/control_ids_core.yaml b/src/libcamera/control_ids_core.yaml
> > index cf40771d3896..04dcc4af67fc 100644
> > --- a/src/libcamera/control_ids_core.yaml
> > +++ b/src/libcamera/control_ids_core.yaml
> > @@ -252,9 +252,12 @@ controls:
> >    - AwbEnable:
> >        type: bool
> >        description: |
> > -        Enable or disable the AWB.
> > +        Enable or disable the AWB. Disabling AWB stops updates to the
> > +        ColourGains and to the ColourCorrectionMatrix.
> 
> Please split this in two paragraphs. The first paragraph is translated
> to a \brief doxygen command, and should be a single sentence. Same
> below.
> 
> I would like to clarify this a bit. Here's an attempt, is it what you
> mean ?
> 
> 	Enable or disable the AWB.
> 
> 	When AWB is enabled, the algorithm estimates the colour	temperature of
> 	the scene, and computes colour gains and the colour correction matrix
> 	automatically. The computed colour temperate, gains and correction
> 	matrix are reported in metadata. The corresponding controls are ignored
> 	if set in a request.
> 
> 	When AWB is disabled, the colour temperature, gains and correction
> 	matrix are not updated automatically and can be set manually in
> 	requests.

Looks good, I'll apply that.

> 
> >  
> > +        \sa ColourCorrectionMatrix
> >          \sa ColourGains
> > +        \sa ColourTemperature
> >  
> >    # AwbMode needs further attention:
> >    # - Auto-generate max enum value.
> > @@ -309,13 +312,24 @@ controls:
> >          disabled.
> >  
> >          \sa AwbEnable
> > +        \sa ColourTemperature
> >        size: [2]
> >  
> >    - ColourTemperature:
> >        type: int32_t
> > -      description: Report the current estimate of the colour temperature, in
> > -        kelvin, for this frame. The ColourTemperature control can only be
> > -        returned in metadata.
> > +      description: |
> > +        Report the current estimate of the colour temperature, in kelvin, for
> > +        this frame. An implementation may also allow this control to be set when
> 
> s/also //
> 
> > +        AWB is disabled. In that case ColourGains and the ColourCorrectionMatrix
> > +        get set accordingly. If either ColourGains or ColourCorrectionMatrix are
> > +        specified at the same time, they take precedence.
> 
> maybe "they take precedence, and the ColourTemperature is ignored" ? Or,
> if an application sets ColourTemperature and ColourGains but not
> ColourCorrectionMatrix, do you expect the implementation to apply the
> requested ColourGains and set ColourCorrectionMatrix based on the
> temperature ?

The latter is exactly what happens. The following table lists the
possible options:

CT -> CG(CT), CCM(CT)
CT, CG -> CG, CCM(CT)
CT, CCM -> CG(CT), CCM
CT, CG, CCM -> CG, CCM

Do you have a nice sentence for that?

> 
> > +
> > +        The metadata will only report measured colour temperature values when
> > +        available, even if set manually.
> 
> I'm not sure to understand this.

This is based on the comment from Kieran:
https://patchwork.libcamera.org/patch/20771/#30590 He wanted to prepare
for cases (RPi) where no temperature gets estimated. Only measurements
are returned in metadata. Manually set temperature is not reflected in
the metadata. This has the nice side effect, that you can set
AwbEnable=false, and still get temperature estimations in the metadata.

> 
> > +
> > +        \sa AwbEnable
> > +        \sa ColourCorrectionMatrix
> > +        \sa ColourGains
> >  
> >    - Saturation:
> >        type: float
> > @@ -365,6 +379,8 @@ controls:
> >          transformation. The 3x3 matrix is stored in conventional reading
> >          order in an array of 9 floating point values.
> >  
> > +        \sa AwbEnable
> > +        \sa ColourTemperature
> >        size: [3,3]
> >  
> >    - ScalerCrop:
> 
> -- 
> Regards,
> 
> Laurent Pinchart

Hi Stefan,

(CC'ing David)

On Fri, Aug 30, 2024 at 07:58:31AM +0200, Stefan Klug wrote:
> On Fri, Aug 30, 2024 at 02:01:19AM +0300, Laurent Pinchart wrote:
> > On Tue, Aug 13, 2024 at 10:44:18AM +0200, Stefan Klug wrote:
> > > For manual control it is helpful to be able to specify a fixed colour
> > > temperature. It also provides an easy way to apply the temperature
> > > specific CCMs and colour gains that are contained in the tuning files.
> > > 
> > > Document this and update the control dependencies.
> > > 
> > > Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com>
> > > ---
> > >  src/libcamera/control_ids_core.yaml | 24 ++++++++++++++++++++----
> > >  1 file changed, 20 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/src/libcamera/control_ids_core.yaml b/src/libcamera/control_ids_core.yaml
> > > index cf40771d3896..04dcc4af67fc 100644
> > > --- a/src/libcamera/control_ids_core.yaml
> > > +++ b/src/libcamera/control_ids_core.yaml
> > > @@ -252,9 +252,12 @@ controls:
> > >    - AwbEnable:
> > >        type: bool
> > >        description: |
> > > -        Enable or disable the AWB.
> > > +        Enable or disable the AWB. Disabling AWB stops updates to the
> > > +        ColourGains and to the ColourCorrectionMatrix.
> > 
> > Please split this in two paragraphs. The first paragraph is translated
> > to a \brief doxygen command, and should be a single sentence. Same
> > below.
> > 
> > I would like to clarify this a bit. Here's an attempt, is it what you
> > mean ?
> > 
> > 	Enable or disable the AWB.
> > 
> > 	When AWB is enabled, the algorithm estimates the colour	temperature of
> > 	the scene, and computes colour gains and the colour correction matrix
> > 	automatically. The computed colour temperate, gains and correction
> > 	matrix are reported in metadata. The corresponding controls are ignored
> > 	if set in a request.
> > 
> > 	When AWB is disabled, the colour temperature, gains and correction
> > 	matrix are not updated automatically and can be set manually in
> > 	requests.
> 
> Looks good, I'll apply that.
> 
> > >  
> > > +        \sa ColourCorrectionMatrix
> > >          \sa ColourGains
> > > +        \sa ColourTemperature
> > >  
> > >    # AwbMode needs further attention:
> > >    # - Auto-generate max enum value.
> > > @@ -309,13 +312,24 @@ controls:
> > >          disabled.
> > >  
> > >          \sa AwbEnable
> > > +        \sa ColourTemperature
> > >        size: [2]
> > >  
> > >    - ColourTemperature:
> > >        type: int32_t
> > > -      description: Report the current estimate of the colour temperature, in
> > > -        kelvin, for this frame. The ColourTemperature control can only be
> > > -        returned in metadata.
> > > +      description: |
> > > +        Report the current estimate of the colour temperature, in kelvin, for
> > > +        this frame. An implementation may also allow this control to be set when
> > 
> > s/also //
> > 
> > > +        AWB is disabled. In that case ColourGains and the ColourCorrectionMatrix
> > > +        get set accordingly. If either ColourGains or ColourCorrectionMatrix are
> > > +        specified at the same time, they take precedence.
> > 
> > maybe "they take precedence, and the ColourTemperature is ignored" ? Or,
> > if an application sets ColourTemperature and ColourGains but not
> > ColourCorrectionMatrix, do you expect the implementation to apply the
> > requested ColourGains and set ColourCorrectionMatrix based on the
> > temperature ?
> 
> The latter is exactly what happens. The following table lists the
> possible options:
> 
> CT -> CG(CT), CCM(CT)
> CT, CG -> CG, CCM(CT)
> CT, CCM -> CG(CT), CCM
> CT, CG, CCM -> CG, CCM

David, is this the behaviour you would also expect for Raspberry Pi ?

> Do you have a nice sentence for that?

/me checks... I have a set of French proverbs, but none of the seem very
appropriate. Sorry :-)

> > > +
> > > +        The metadata will only report measured colour temperature values when
> > > +        available, even if set manually.
> > 
> > I'm not sure to understand this.
> 
> This is based on the comment from Kieran:
> https://patchwork.libcamera.org/patch/20771/#30590 He wanted to prepare
> for cases (RPi) where no temperature gets estimated. Only measurements
> are returned in metadata. Manually set temperature is not reflected in
> the metadata. This has the nice side effect, that you can set
> AwbEnable=false, and still get temperature estimations in the metadata.

This means that whether or not the estimated colour temperature will be
returned in metadata will be platform-dependent. Can we avoid that ? It
makes writing portable applications much more difficult.

My other concern is that metadata is supposed to report the setting
applied to a frame. The general rule is that, if a control can be set,
the value that has been set for a frame is reported in metadata. There
are exception for trigger-like controls. As this example clearly shows,
having multiple controls that ultimately set the same values is also
problematic from this point of view. Do we need to set a rule that
higher-level controls that get translated to lower-level controls are
never reported in metadata ?

If we do that, then we'll have ColourTemperature as a control being
defined differently from ColourTemperature as metadata. I'm not sure I
like it much. Should we have two different controls ?

> > > +
> > > +        \sa AwbEnable
> > > +        \sa ColourCorrectionMatrix
> > > +        \sa ColourGains
> > >  
> > >    - Saturation:
> > >        type: float
> > > @@ -365,6 +379,8 @@ controls:
> > >          transformation. The 3x3 matrix is stored in conventional reading
> > >          order in an array of 9 floating point values.
> > >  
> > > +        \sa AwbEnable
> > > +        \sa ColourTemperature
> > >        size: [3,3]
> > >  
> > >    - ScalerCrop:

Hi Laurent,

On Fri, Aug 30, 2024 at 01:15:55PM +0300, Laurent Pinchart wrote:
> Hi Stefan,
> 
> (CC'ing David)
> 
> On Fri, Aug 30, 2024 at 07:58:31AM +0200, Stefan Klug wrote:
> > On Fri, Aug 30, 2024 at 02:01:19AM +0300, Laurent Pinchart wrote:
> > > On Tue, Aug 13, 2024 at 10:44:18AM +0200, Stefan Klug wrote:
> > > > For manual control it is helpful to be able to specify a fixed colour
> > > > temperature. It also provides an easy way to apply the temperature
> > > > specific CCMs and colour gains that are contained in the tuning files.
> > > > 
> > > > Document this and update the control dependencies.
> > > > 
> > > > Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com>
> > > > ---
> > > >  src/libcamera/control_ids_core.yaml | 24 ++++++++++++++++++++----
> > > >  1 file changed, 20 insertions(+), 4 deletions(-)
> > > > 
> > > > diff --git a/src/libcamera/control_ids_core.yaml b/src/libcamera/control_ids_core.yaml
> > > > index cf40771d3896..04dcc4af67fc 100644
> > > > --- a/src/libcamera/control_ids_core.yaml
> > > > +++ b/src/libcamera/control_ids_core.yaml
> > > > @@ -252,9 +252,12 @@ controls:
> > > >    - AwbEnable:
> > > >        type: bool
> > > >        description: |
> > > > -        Enable or disable the AWB.
> > > > +        Enable or disable the AWB. Disabling AWB stops updates to the
> > > > +        ColourGains and to the ColourCorrectionMatrix.
> > > 
> > > Please split this in two paragraphs. The first paragraph is translated
> > > to a \brief doxygen command, and should be a single sentence. Same
> > > below.
> > > 
> > > I would like to clarify this a bit. Here's an attempt, is it what you
> > > mean ?
> > > 
> > > 	Enable or disable the AWB.
> > > 
> > > 	When AWB is enabled, the algorithm estimates the colour	temperature of
> > > 	the scene, and computes colour gains and the colour correction matrix
> > > 	automatically. The computed colour temperate, gains and correction
> > > 	matrix are reported in metadata. The corresponding controls are ignored
> > > 	if set in a request.
> > > 
> > > 	When AWB is disabled, the colour temperature, gains and correction
> > > 	matrix are not updated automatically and can be set manually in
> > > 	requests.
> > 
> > Looks good, I'll apply that.
> > 
> > > >  
> > > > +        \sa ColourCorrectionMatrix
> > > >          \sa ColourGains
> > > > +        \sa ColourTemperature
> > > >  
> > > >    # AwbMode needs further attention:
> > > >    # - Auto-generate max enum value.
> > > > @@ -309,13 +312,24 @@ controls:
> > > >          disabled.
> > > >  
> > > >          \sa AwbEnable
> > > > +        \sa ColourTemperature
> > > >        size: [2]
> > > >  
> > > >    - ColourTemperature:
> > > >        type: int32_t
> > > > -      description: Report the current estimate of the colour temperature, in
> > > > -        kelvin, for this frame. The ColourTemperature control can only be
> > > > -        returned in metadata.
> > > > +      description: |
> > > > +        Report the current estimate of the colour temperature, in kelvin, for
> > > > +        this frame. An implementation may also allow this control to be set when
> > > 
> > > s/also //
> > > 
> > > > +        AWB is disabled. In that case ColourGains and the ColourCorrectionMatrix
> > > > +        get set accordingly. If either ColourGains or ColourCorrectionMatrix are
> > > > +        specified at the same time, they take precedence.
> > > 
> > > maybe "they take precedence, and the ColourTemperature is ignored" ? Or,
> > > if an application sets ColourTemperature and ColourGains but not
> > > ColourCorrectionMatrix, do you expect the implementation to apply the
> > > requested ColourGains and set ColourCorrectionMatrix based on the
> > > temperature ?
> > 
> > The latter is exactly what happens. The following table lists the
> > possible options:
> > 
> > CT -> CG(CT), CCM(CT)
> > CT, CG -> CG, CCM(CT)
> > CT, CCM -> CG(CT), CCM
> > CT, CG, CCM -> CG, CCM
> 
> David, is this the behaviour you would also expect for Raspberry Pi ?
> 
> > Do you have a nice sentence for that?
> 
> /me checks... I have a set of French proverbs, but none of the seem very
> appropriate. Sorry :-)
>

What about "If ColourGains and ColourTemperature are specified at the
same time, ColourGains takes precedence. The same applies to
ColourCorrectionMatrix."?

We can discuss the final wording after feedback from David.

> 
> > > > +
> > > > +        The metadata will only report measured colour temperature values when
> > > > +        available, even if set manually.
> > > 
> > > I'm not sure to understand this.
> > 
> > This is based on the comment from Kieran:
> > https://patchwork.libcamera.org/patch/20771/#30590 He wanted to prepare
> > for cases (RPi) where no temperature gets estimated. Only measurements
> > are returned in metadata. Manually set temperature is not reflected in
> > the metadata. This has the nice side effect, that you can set
> > AwbEnable=false, and still get temperature estimations in the metadata.
> 
> This means that whether or not the estimated colour temperature will be
> returned in metadata will be platform-dependent. Can we avoid that ? It
> makes writing portable applications much more difficult.
> 
> My other concern is that metadata is supposed to report the setting
> applied to a frame. The general rule is that, if a control can be set,
> the value that has been set for a frame is reported in metadata. There
> are exception for trigger-like controls. As this example clearly shows,
> having multiple controls that ultimately set the same values is also
> problematic from this point of view. Do we need to set a rule that
> higher-level controls that get translated to lower-level controls are
> never reported in metadata ?
> 
> If we do that, then we'll have ColourTemperature as a control being
> defined differently from ColourTemperature as metadata. I'm not sure I
> like it much. Should we have two different controls ?
>

We could split that to "MeasuredColourTemperature" and
"AppliedColorTemperature". But there are always cases where one of them
(or both) is not available (as discussed on Patch 3). I think on rkisp
we could ensure that MeasuredColourTemperature is always available and
contains "something" as the statistics are always available. But in the
end as a user I'd prefer to know when the algorithm failed to deduce a
valid colour temperature.

Regards,
Stefan

> 
> > > > +
> > > > +        \sa AwbEnable
> > > > +        \sa ColourCorrectionMatrix
> > > > +        \sa ColourGains
> > > >  
> > > >    - Saturation:
> > > >        type: float
> > > > @@ -365,6 +379,8 @@ controls:
> > > >          transformation. The 3x3 matrix is stored in conventional reading
> > > >          order in an array of 9 floating point values.
> > > >  
> > > > +        \sa AwbEnable
> > > > +        \sa ColourTemperature
> > > >        size: [3,3]
> > > >  
> > > >    - ScalerCrop:
> 
> -- 
> Regards,
> 
> Laurent Pinchart

Hi everyone

On Fri, 30 Aug 2024 at 12:21, Stefan Klug <stefan.klug@ideasonboard.com> wrote:
>
> Hi Laurent,
>
> On Fri, Aug 30, 2024 at 01:15:55PM +0300, Laurent Pinchart wrote:
> > Hi Stefan,
> >
> > (CC'ing David)
> >
> > On Fri, Aug 30, 2024 at 07:58:31AM +0200, Stefan Klug wrote:
> > > On Fri, Aug 30, 2024 at 02:01:19AM +0300, Laurent Pinchart wrote:
> > > > On Tue, Aug 13, 2024 at 10:44:18AM +0200, Stefan Klug wrote:
> > > > > For manual control it is helpful to be able to specify a fixed colour
> > > > > temperature. It also provides an easy way to apply the temperature
> > > > > specific CCMs and colour gains that are contained in the tuning files.
> > > > >
> > > > > Document this and update the control dependencies.
> > > > >
> > > > > Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com>
> > > > > ---
> > > > >  src/libcamera/control_ids_core.yaml | 24 ++++++++++++++++++++----
> > > > >  1 file changed, 20 insertions(+), 4 deletions(-)
> > > > >
> > > > > diff --git a/src/libcamera/control_ids_core.yaml b/src/libcamera/control_ids_core.yaml
> > > > > index cf40771d3896..04dcc4af67fc 100644
> > > > > --- a/src/libcamera/control_ids_core.yaml
> > > > > +++ b/src/libcamera/control_ids_core.yaml
> > > > > @@ -252,9 +252,12 @@ controls:
> > > > >    - AwbEnable:
> > > > >        type: bool
> > > > >        description: |
> > > > > -        Enable or disable the AWB.
> > > > > +        Enable or disable the AWB. Disabling AWB stops updates to the
> > > > > +        ColourGains and to the ColourCorrectionMatrix.
> > > >
> > > > Please split this in two paragraphs. The first paragraph is translated
> > > > to a \brief doxygen command, and should be a single sentence. Same
> > > > below.
> > > >
> > > > I would like to clarify this a bit. Here's an attempt, is it what you
> > > > mean ?
> > > >
> > > >   Enable or disable the AWB.
> > > >
> > > >   When AWB is enabled, the algorithm estimates the colour temperature of
> > > >   the scene, and computes colour gains and the colour correction matrix
> > > >   automatically. The computed colour temperate, gains and correction
> > > >   matrix are reported in metadata. The corresponding controls are ignored
> > > >   if set in a request.
> > > >
> > > >   When AWB is disabled, the colour temperature, gains and correction
> > > >   matrix are not updated automatically and can be set manually in
> > > >   requests.
> > >
> > > Looks good, I'll apply that.
> > >
> > > > >
> > > > > +        \sa ColourCorrectionMatrix
> > > > >          \sa ColourGains
> > > > > +        \sa ColourTemperature
> > > > >
> > > > >    # AwbMode needs further attention:
> > > > >    # - Auto-generate max enum value.
> > > > > @@ -309,13 +312,24 @@ controls:
> > > > >          disabled.
> > > > >
> > > > >          \sa AwbEnable
> > > > > +        \sa ColourTemperature
> > > > >        size: [2]
> > > > >
> > > > >    - ColourTemperature:
> > > > >        type: int32_t
> > > > > -      description: Report the current estimate of the colour temperature, in
> > > > > -        kelvin, for this frame. The ColourTemperature control can only be
> > > > > -        returned in metadata.
> > > > > +      description: |
> > > > > +        Report the current estimate of the colour temperature, in kelvin, for
> > > > > +        this frame. An implementation may also allow this control to be set when
> > > >
> > > > s/also //
> > > >
> > > > > +        AWB is disabled. In that case ColourGains and the ColourCorrectionMatrix
> > > > > +        get set accordingly. If either ColourGains or ColourCorrectionMatrix are
> > > > > +        specified at the same time, they take precedence.
> > > >
> > > > maybe "they take precedence, and the ColourTemperature is ignored" ? Or,
> > > > if an application sets ColourTemperature and ColourGains but not
> > > > ColourCorrectionMatrix, do you expect the implementation to apply the
> > > > requested ColourGains and set ColourCorrectionMatrix based on the
> > > > temperature ?
> > >
> > > The latter is exactly what happens. The following table lists the
> > > possible options:
> > >
> > > CT -> CG(CT), CCM(CT)
> > > CT, CG -> CG, CCM(CT)
> > > CT, CCM -> CG(CT), CCM
> > > CT, CG, CCM -> CG, CCM
> >
> > David, is this the behaviour you would also expect for Raspberry Pi ?

I'm guessing the question here is really what to do if an application
sets both CT and CG together? The other cases seem fairly
uncontroversial (?).

For us, I'm not sure it really makes much sense to supply both CT and
CG at once. When someone sets CG, the algorithm estimates the CT and
passes this to other algorithms, like lens shading and CCM. (So we
actually have a "CG -> CG, CT(CG), CCM(CT)" kind of case going on.)

When I add this new control, it will calculate CG from the calibrated
colour temperature curve in the camera tuning and use those, and pass
the CT to those other algorithms (so like the first row in the table).

I don't think I particularly want to implement cases where it takes a
CG value, uses them, and also a random CT which it then passes on?
Possibly I'd rather leave these cases (where we have both CT and CG on
the LHS) as either "implementation dependent" or just "undefined", and
recommend setting one or other.

Does that help or just confuse further?

Thanks!
David

> >
> > > Do you have a nice sentence for that?
> >
> > /me checks... I have a set of French proverbs, but none of the seem very
> > appropriate. Sorry :-)
> >
>
> What about "If ColourGains and ColourTemperature are specified at the
> same time, ColourGains takes precedence. The same applies to
> ColourCorrectionMatrix."?
>
> We can discuss the final wording after feedback from David.
>
> >
> > > > > +
> > > > > +        The metadata will only report measured colour temperature values when
> > > > > +        available, even if set manually.
> > > >
> > > > I'm not sure to understand this.
> > >
> > > This is based on the comment from Kieran:
> > > https://patchwork.libcamera.org/patch/20771/#30590 He wanted to prepare
> > > for cases (RPi) where no temperature gets estimated. Only measurements
> > > are returned in metadata. Manually set temperature is not reflected in
> > > the metadata. This has the nice side effect, that you can set
> > > AwbEnable=false, and still get temperature estimations in the metadata.
> >
> > This means that whether or not the estimated colour temperature will be
> > returned in metadata will be platform-dependent. Can we avoid that ? It
> > makes writing portable applications much more difficult.
> >
> > My other concern is that metadata is supposed to report the setting
> > applied to a frame. The general rule is that, if a control can be set,
> > the value that has been set for a frame is reported in metadata. There
> > are exception for trigger-like controls. As this example clearly shows,
> > having multiple controls that ultimately set the same values is also
> > problematic from this point of view. Do we need to set a rule that
> > higher-level controls that get translated to lower-level controls are
> > never reported in metadata ?
> >
> > If we do that, then we'll have ColourTemperature as a control being
> > defined differently from ColourTemperature as metadata. I'm not sure I
> > like it much. Should we have two different controls ?
> >
>
> We could split that to "MeasuredColourTemperature" and
> "AppliedColorTemperature". But there are always cases where one of them
> (or both) is not available (as discussed on Patch 3). I think on rkisp
> we could ensure that MeasuredColourTemperature is always available and
> contains "something" as the statistics are always available. But in the
> end as a user I'd prefer to know when the algorithm failed to deduce a
> valid colour temperature.
>
> Regards,
> Stefan
>
> >
> > > > > +
> > > > > +        \sa AwbEnable
> > > > > +        \sa ColourCorrectionMatrix
> > > > > +        \sa ColourGains
> > > > >
> > > > >    - Saturation:
> > > > >        type: float
> > > > > @@ -365,6 +379,8 @@ controls:
> > > > >          transformation. The 3x3 matrix is stored in conventional reading
> > > > >          order in an array of 9 floating point values.
> > > > >
> > > > > +        \sa AwbEnable
> > > > > +        \sa ColourTemperature
> > > > >        size: [3,3]
> > > > >
> > > > >    - ScalerCrop:
> >
> > --
> > Regards,
> >
> > Laurent Pinchart

On Fri, Aug 30, 2024 at 04:31:50PM +0100, David Plowman wrote:
> On Fri, 30 Aug 2024 at 12:21, Stefan Klug wrote:
> > On Fri, Aug 30, 2024 at 01:15:55PM +0300, Laurent Pinchart wrote:
> > > On Fri, Aug 30, 2024 at 07:58:31AM +0200, Stefan Klug wrote:
> > > > On Fri, Aug 30, 2024 at 02:01:19AM +0300, Laurent Pinchart wrote:
> > > > > On Tue, Aug 13, 2024 at 10:44:18AM +0200, Stefan Klug wrote:
> > > > > > For manual control it is helpful to be able to specify a fixed colour
> > > > > > temperature. It also provides an easy way to apply the temperature
> > > > > > specific CCMs and colour gains that are contained in the tuning files.
> > > > > >
> > > > > > Document this and update the control dependencies.
> > > > > >
> > > > > > Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com>
> > > > > > ---
> > > > > >  src/libcamera/control_ids_core.yaml | 24 ++++++++++++++++++++----
> > > > > >  1 file changed, 20 insertions(+), 4 deletions(-)
> > > > > >
> > > > > > diff --git a/src/libcamera/control_ids_core.yaml b/src/libcamera/control_ids_core.yaml
> > > > > > index cf40771d3896..04dcc4af67fc 100644
> > > > > > --- a/src/libcamera/control_ids_core.yaml
> > > > > > +++ b/src/libcamera/control_ids_core.yaml
> > > > > > @@ -252,9 +252,12 @@ controls:
> > > > > >    - AwbEnable:
> > > > > >        type: bool
> > > > > >        description: |
> > > > > > -        Enable or disable the AWB.
> > > > > > +        Enable or disable the AWB. Disabling AWB stops updates to the
> > > > > > +        ColourGains and to the ColourCorrectionMatrix.
> > > > >
> > > > > Please split this in two paragraphs. The first paragraph is translated
> > > > > to a \brief doxygen command, and should be a single sentence. Same
> > > > > below.
> > > > >
> > > > > I would like to clarify this a bit. Here's an attempt, is it what you
> > > > > mean ?
> > > > >
> > > > >   Enable or disable the AWB.
> > > > >
> > > > >   When AWB is enabled, the algorithm estimates the colour temperature of
> > > > >   the scene, and computes colour gains and the colour correction matrix
> > > > >   automatically. The computed colour temperate, gains and correction
> > > > >   matrix are reported in metadata. The corresponding controls are ignored
> > > > >   if set in a request.
> > > > >
> > > > >   When AWB is disabled, the colour temperature, gains and correction
> > > > >   matrix are not updated automatically and can be set manually in
> > > > >   requests.
> > > >
> > > > Looks good, I'll apply that.
> > > >
> > > > > >
> > > > > > +        \sa ColourCorrectionMatrix
> > > > > >          \sa ColourGains
> > > > > > +        \sa ColourTemperature
> > > > > >
> > > > > >    # AwbMode needs further attention:
> > > > > >    # - Auto-generate max enum value.
> > > > > > @@ -309,13 +312,24 @@ controls:
> > > > > >          disabled.
> > > > > >
> > > > > >          \sa AwbEnable
> > > > > > +        \sa ColourTemperature
> > > > > >        size: [2]
> > > > > >
> > > > > >    - ColourTemperature:
> > > > > >        type: int32_t
> > > > > > -      description: Report the current estimate of the colour temperature, in
> > > > > > -        kelvin, for this frame. The ColourTemperature control can only be
> > > > > > -        returned in metadata.
> > > > > > +      description: |
> > > > > > +        Report the current estimate of the colour temperature, in kelvin, for
> > > > > > +        this frame. An implementation may also allow this control to be set when
> > > > >
> > > > > s/also //
> > > > >
> > > > > > +        AWB is disabled. In that case ColourGains and the ColourCorrectionMatrix
> > > > > > +        get set accordingly. If either ColourGains or ColourCorrectionMatrix are
> > > > > > +        specified at the same time, they take precedence.
> > > > >
> > > > > maybe "they take precedence, and the ColourTemperature is ignored" ? Or,
> > > > > if an application sets ColourTemperature and ColourGains but not
> > > > > ColourCorrectionMatrix, do you expect the implementation to apply the
> > > > > requested ColourGains and set ColourCorrectionMatrix based on the
> > > > > temperature ?
> > > >
> > > > The latter is exactly what happens. The following table lists the
> > > > possible options:
> > > >
> > > > CT -> CG(CT), CCM(CT)
> > > > CT, CG -> CG, CCM(CT)
> > > > CT, CCM -> CG(CT), CCM
> > > > CT, CG, CCM -> CG, CCM
> > >
> > > David, is this the behaviour you would also expect for Raspberry Pi ?
> 
> I'm guessing the question here is really what to do if an application
> sets both CT and CG together? The other cases seem fairly
> uncontroversial (?).

As far as I understand, for the rkisp1, the colour gains and the CCM are
both calculated based on the colour temperature. The case where the
application sets CT and CG is conceptually as problematic as the case
where it sets CT and CCM. Stefan, is that correct ?

> For us, I'm not sure it really makes much sense to supply both CT and
> CG at once. When someone sets CG, the algorithm estimates the CT and
> passes this to other algorithms, like lens shading and CCM. (So we
> actually have a "CG -> CG, CT(CG), CCM(CT)" kind of case going on.)

When an application sets CG, does the algorithm estimate CT from the
stats, or from the CG alone for RPi ? Stefan, how about your plans for
rkisp1 ?

> When I add this new control, it will calculate CG from the calibrated
> colour temperature curve in the camera tuning and use those, and pass
> the CT to those other algorithms (so like the first row in the table).

That's the main use, and I think we all agree on the behaviour. It seems
quite uncontroversial.

> I don't think I particularly want to implement cases where it takes a
> CG value, uses them, and also a random CT which it then passes on?
> Possibly I'd rather leave these cases (where we have both CT and CG on
> the LHS) as either "implementation dependent" or just "undefined", and
> recommend setting one or other.

I dislike implementation-dependent behaviours if we can avoid them, at
least in cases that we consider valid use cases. Is there a valid use
case for setting CT along with CG or CCM ? It sounds to me like there
wouldn't be one for RPi. Stefan, how about you ?

> Does that help or just confuse further?

Let's see how the discussion progresses :-) Thank you for your input.

> > > > Do you have a nice sentence for that?
> > >
> > > /me checks... I have a set of French proverbs, but none of the seem very
> > > appropriate. Sorry :-)
> >
> > What about "If ColourGains and ColourTemperature are specified at the
> > same time, ColourGains takes precedence. The same applies to
> > ColourCorrectionMatrix."?
> >
> > We can discuss the final wording after feedback from David.
> >
> > > > > > +
> > > > > > +        The metadata will only report measured colour temperature values when
> > > > > > +        available, even if set manually.
> > > > >
> > > > > I'm not sure to understand this.
> > > >
> > > > This is based on the comment from Kieran:
> > > > https://patchwork.libcamera.org/patch/20771/#30590 He wanted to prepare
> > > > for cases (RPi) where no temperature gets estimated. Only measurements
> > > > are returned in metadata. Manually set temperature is not reflected in
> > > > the metadata. This has the nice side effect, that you can set
> > > > AwbEnable=false, and still get temperature estimations in the metadata.
> > >
> > > This means that whether or not the estimated colour temperature will be
> > > returned in metadata will be platform-dependent. Can we avoid that ? It
> > > makes writing portable applications much more difficult.
> > >
> > > My other concern is that metadata is supposed to report the setting
> > > applied to a frame. The general rule is that, if a control can be set,
> > > the value that has been set for a frame is reported in metadata. There
> > > are exception for trigger-like controls. As this example clearly shows,
> > > having multiple controls that ultimately set the same values is also
> > > problematic from this point of view. Do we need to set a rule that
> > > higher-level controls that get translated to lower-level controls are
> > > never reported in metadata ?
> > >
> > > If we do that, then we'll have ColourTemperature as a control being
> > > defined differently from ColourTemperature as metadata. I'm not sure I
> > > like it much. Should we have two different controls ?
> >
> > We could split that to "MeasuredColourTemperature" and
> > "AppliedColorTemperature". But there are always cases where one of them
> > (or both) is not available (as discussed on Patch 3). I think on rkisp
> > we could ensure that MeasuredColourTemperature is always available and
> > contains "something" as the statistics are always available. But in the
> > end as a user I'd prefer to know when the algorithm failed to deduce a
> > valid colour temperature.

If the algorithm failed to estimate the colour temperature, that should
be indicated by the absence of an estimated colour temperature in
metadata.

David, why do you (if I understand correctly) stop estimating the colour
temperature from the statistics in manual AWB mode ?

> > > > > > +
> > > > > > +        \sa AwbEnable
> > > > > > +        \sa ColourCorrectionMatrix
> > > > > > +        \sa ColourGains
> > > > > >
> > > > > >    - Saturation:
> > > > > >        type: float
> > > > > > @@ -365,6 +379,8 @@ controls:
> > > > > >          transformation. The 3x3 matrix is stored in conventional reading
> > > > > >          order in an array of 9 floating point values.
> > > > > >
> > > > > > +        \sa AwbEnable
> > > > > > +        \sa ColourTemperature
> > > > > >        size: [3,3]
> > > > > >
> > > > > >    - ScalerCrop:

Hi Laurent,

David's away this week, so I'll answer on his behalf.

On Sat, 31 Aug 2024 at 16:16, Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
>
> On Fri, Aug 30, 2024 at 04:31:50PM +0100, David Plowman wrote:
> > On Fri, 30 Aug 2024 at 12:21, Stefan Klug wrote:
> > > On Fri, Aug 30, 2024 at 01:15:55PM +0300, Laurent Pinchart wrote:
> > > > On Fri, Aug 30, 2024 at 07:58:31AM +0200, Stefan Klug wrote:
> > > > > On Fri, Aug 30, 2024 at 02:01:19AM +0300, Laurent Pinchart wrote:
> > > > > > On Tue, Aug 13, 2024 at 10:44:18AM +0200, Stefan Klug wrote:
> > > > > > > For manual control it is helpful to be able to specify a fixed colour
> > > > > > > temperature. It also provides an easy way to apply the temperature
> > > > > > > specific CCMs and colour gains that are contained in the tuning files.
> > > > > > >
> > > > > > > Document this and update the control dependencies.
> > > > > > >
> > > > > > > Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com>
> > > > > > > ---
> > > > > > >  src/libcamera/control_ids_core.yaml | 24 ++++++++++++++++++++----
> > > > > > >  1 file changed, 20 insertions(+), 4 deletions(-)
> > > > > > >
> > > > > > > diff --git a/src/libcamera/control_ids_core.yaml b/src/libcamera/control_ids_core.yaml
> > > > > > > index cf40771d3896..04dcc4af67fc 100644
> > > > > > > --- a/src/libcamera/control_ids_core.yaml
> > > > > > > +++ b/src/libcamera/control_ids_core.yaml
> > > > > > > @@ -252,9 +252,12 @@ controls:
> > > > > > >    - AwbEnable:
> > > > > > >        type: bool
> > > > > > >        description: |
> > > > > > > -        Enable or disable the AWB.
> > > > > > > +        Enable or disable the AWB. Disabling AWB stops updates to the
> > > > > > > +        ColourGains and to the ColourCorrectionMatrix.
> > > > > >
> > > > > > Please split this in two paragraphs. The first paragraph is translated
> > > > > > to a \brief doxygen command, and should be a single sentence. Same
> > > > > > below.
> > > > > >
> > > > > > I would like to clarify this a bit. Here's an attempt, is it what you
> > > > > > mean ?
> > > > > >
> > > > > >   Enable or disable the AWB.
> > > > > >
> > > > > >   When AWB is enabled, the algorithm estimates the colour temperature of
> > > > > >   the scene, and computes colour gains and the colour correction matrix
> > > > > >   automatically. The computed colour temperate, gains and correction
> > > > > >   matrix are reported in metadata. The corresponding controls are ignored
> > > > > >   if set in a request.
> > > > > >
> > > > > >   When AWB is disabled, the colour temperature, gains and correction
> > > > > >   matrix are not updated automatically and can be set manually in
> > > > > >   requests.
> > > > >
> > > > > Looks good, I'll apply that.
> > > > >
> > > > > > >
> > > > > > > +        \sa ColourCorrectionMatrix
> > > > > > >          \sa ColourGains
> > > > > > > +        \sa ColourTemperature
> > > > > > >
> > > > > > >    # AwbMode needs further attention:
> > > > > > >    # - Auto-generate max enum value.
> > > > > > > @@ -309,13 +312,24 @@ controls:
> > > > > > >          disabled.
> > > > > > >
> > > > > > >          \sa AwbEnable
> > > > > > > +        \sa ColourTemperature
> > > > > > >        size: [2]
> > > > > > >
> > > > > > >    - ColourTemperature:
> > > > > > >        type: int32_t
> > > > > > > -      description: Report the current estimate of the colour temperature, in
> > > > > > > -        kelvin, for this frame. The ColourTemperature control can only be
> > > > > > > -        returned in metadata.
> > > > > > > +      description: |
> > > > > > > +        Report the current estimate of the colour temperature, in kelvin, for
> > > > > > > +        this frame. An implementation may also allow this control to be set when
> > > > > >
> > > > > > s/also //
> > > > > >
> > > > > > > +        AWB is disabled. In that case ColourGains and the ColourCorrectionMatrix
> > > > > > > +        get set accordingly. If either ColourGains or ColourCorrectionMatrix are
> > > > > > > +        specified at the same time, they take precedence.
> > > > > >
> > > > > > maybe "they take precedence, and the ColourTemperature is ignored" ? Or,
> > > > > > if an application sets ColourTemperature and ColourGains but not
> > > > > > ColourCorrectionMatrix, do you expect the implementation to apply the
> > > > > > requested ColourGains and set ColourCorrectionMatrix based on the
> > > > > > temperature ?
> > > > >
> > > > > The latter is exactly what happens. The following table lists the
> > > > > possible options:
> > > > >
> > > > > CT -> CG(CT), CCM(CT)
> > > > > CT, CG -> CG, CCM(CT)
> > > > > CT, CCM -> CG(CT), CCM
> > > > > CT, CG, CCM -> CG, CCM
> > > >
> > > > David, is this the behaviour you would also expect for Raspberry Pi ?
> >
> > I'm guessing the question here is really what to do if an application
> > sets both CT and CG together? The other cases seem fairly
> > uncontroversial (?).
>
> As far as I understand, for the rkisp1, the colour gains and the CCM are
> both calculated based on the colour temperature. The case where the
> application sets CT and CG is conceptually as problematic as the case
> where it sets CT and CCM. Stefan, is that correct ?
>
> > For us, I'm not sure it really makes much sense to supply both CT and
> > CG at once. When someone sets CG, the algorithm estimates the CT and
> > passes this to other algorithms, like lens shading and CCM. (So we
> > actually have a "CG -> CG, CT(CG), CCM(CT)" kind of case going on.)
>
> When an application sets CG, does the algorithm estimate CT from the
> stats, or from the CG alone for RPi ? Stefan, how about your plans for
> rkisp1 ?

When an application sets manual CGs, the algorithm estimates the CT
from the CT-curve in the tuning directly.

>
> > When I add this new control, it will calculate CG from the calibrated
> > colour temperature curve in the camera tuning and use those, and pass
> > the CT to those other algorithms (so like the first row in the table).
>
> That's the main use, and I think we all agree on the behaviour. It seems
> quite uncontroversial.
>
> > I don't think I particularly want to implement cases where it takes a
> > CG value, uses them, and also a random CT which it then passes on?
> > Possibly I'd rather leave these cases (where we have both CT and CG on
> > the LHS) as either "implementation dependent" or just "undefined", and
> > recommend setting one or other.
>
> I dislike implementation-dependent behaviours if we can avoid them, at
> least in cases that we consider valid use cases. Is there a valid use
> case for setting CT along with CG or CCM ? It sounds to me like there
> wouldn't be one for RPi. Stefan, how about you ?

I don't think RPi has a use case that requires the CT and CGs to be both set.

>
> > Does that help or just confuse further?
>
> Let's see how the discussion progresses :-) Thank you for your input.
>
> > > > > Do you have a nice sentence for that?
> > > >
> > > > /me checks... I have a set of French proverbs, but none of the seem very
> > > > appropriate. Sorry :-)
> > >
> > > What about "If ColourGains and ColourTemperature are specified at the
> > > same time, ColourGains takes precedence. The same applies to
> > > ColourCorrectionMatrix."?
> > >
> > > We can discuss the final wording after feedback from David.
> > >
> > > > > > > +
> > > > > > > +        The metadata will only report measured colour temperature values when
> > > > > > > +        available, even if set manually.
> > > > > >
> > > > > > I'm not sure to understand this.
> > > > >
> > > > > This is based on the comment from Kieran:
> > > > > https://patchwork.libcamera.org/patch/20771/#30590 He wanted to prepare
> > > > > for cases (RPi) where no temperature gets estimated. Only measurements
> > > > > are returned in metadata. Manually set temperature is not reflected in
> > > > > the metadata. This has the nice side effect, that you can set
> > > > > AwbEnable=false, and still get temperature estimations in the metadata.
> > > >
> > > > This means that whether or not the estimated colour temperature will be
> > > > returned in metadata will be platform-dependent. Can we avoid that ? It
> > > > makes writing portable applications much more difficult.
> > > >
> > > > My other concern is that metadata is supposed to report the setting
> > > > applied to a frame. The general rule is that, if a control can be set,
> > > > the value that has been set for a frame is reported in metadata. There
> > > > are exception for trigger-like controls. As this example clearly shows,
> > > > having multiple controls that ultimately set the same values is also
> > > > problematic from this point of view. Do we need to set a rule that
> > > > higher-level controls that get translated to lower-level controls are
> > > > never reported in metadata ?
> > > >
> > > > If we do that, then we'll have ColourTemperature as a control being
> > > > defined differently from ColourTemperature as metadata. I'm not sure I
> > > > like it much. Should we have two different controls ?
> > >
> > > We could split that to "MeasuredColourTemperature" and
> > > "AppliedColorTemperature". But there are always cases where one of them
> > > (or both) is not available (as discussed on Patch 3). I think on rkisp
> > > we could ensure that MeasuredColourTemperature is always available and
> > > contains "something" as the statistics are always available. But in the
> > > end as a user I'd prefer to know when the algorithm failed to deduce a
> > > valid colour temperature.
>
> If the algorithm failed to estimate the colour temperature, that should
> be indicated by the absence of an estimated colour temperature in
> metadata.
>
> David, why do you (if I understand correctly) stop estimating the colour
> temperature from the statistics in manual AWB mode ?

I think it's to keep things consistent.  The CT-curve in the tuning
file is taken as the canonical truth. So if manual CGs are applied,
and assuming the users know what they are doing(!), we return a simple
lookup without going through all the computations again.  Of course,
this is simple enough to change in our code if the need arises.

Regards,
Naush

>
> > > > > > > +
> > > > > > > +        \sa AwbEnable
> > > > > > > +        \sa ColourCorrectionMatrix
> > > > > > > +        \sa ColourGains
> > > > > > >
> > > > > > >    - Saturation:
> > > > > > >        type: float
> > > > > > > @@ -365,6 +379,8 @@ controls:
> > > > > > >          transformation. The 3x3 matrix is stored in conventional reading
> > > > > > >          order in an array of 9 floating point values.
> > > > > > >
> > > > > > > +        \sa AwbEnable
> > > > > > > +        \sa ColourTemperature
> > > > > > >        size: [3,3]
> > > > > > >
> > > > > > >    - ScalerCrop:
>
> --
> Regards,
>
> Laurent Pinchart

On Sat, Aug 31, 2024 at 06:16:10PM +0300, Laurent Pinchart wrote:
> On Fri, Aug 30, 2024 at 04:31:50PM +0100, David Plowman wrote:
> > On Fri, 30 Aug 2024 at 12:21, Stefan Klug wrote:
> > > On Fri, Aug 30, 2024 at 01:15:55PM +0300, Laurent Pinchart wrote:
> > > > On Fri, Aug 30, 2024 at 07:58:31AM +0200, Stefan Klug wrote:
> > > > > On Fri, Aug 30, 2024 at 02:01:19AM +0300, Laurent Pinchart wrote:
> > > > > > On Tue, Aug 13, 2024 at 10:44:18AM +0200, Stefan Klug wrote:
> > > > > > > For manual control it is helpful to be able to specify a fixed colour
> > > > > > > temperature. It also provides an easy way to apply the temperature
> > > > > > > specific CCMs and colour gains that are contained in the tuning files.
> > > > > > >
> > > > > > > Document this and update the control dependencies.
> > > > > > >
> > > > > > > Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com>
> > > > > > > ---
> > > > > > >  src/libcamera/control_ids_core.yaml | 24 ++++++++++++++++++++----
> > > > > > >  1 file changed, 20 insertions(+), 4 deletions(-)
> > > > > > >
> > > > > > > diff --git a/src/libcamera/control_ids_core.yaml b/src/libcamera/control_ids_core.yaml
> > > > > > > index cf40771d3896..04dcc4af67fc 100644
> > > > > > > --- a/src/libcamera/control_ids_core.yaml
> > > > > > > +++ b/src/libcamera/control_ids_core.yaml
> > > > > > > @@ -252,9 +252,12 @@ controls:
> > > > > > >    - AwbEnable:
> > > > > > >        type: bool
> > > > > > >        description: |
> > > > > > > -        Enable or disable the AWB.
> > > > > > > +        Enable or disable the AWB. Disabling AWB stops updates to the
> > > > > > > +        ColourGains and to the ColourCorrectionMatrix.
> > > > > >
> > > > > > Please split this in two paragraphs. The first paragraph is translated
> > > > > > to a \brief doxygen command, and should be a single sentence. Same
> > > > > > below.
> > > > > >
> > > > > > I would like to clarify this a bit. Here's an attempt, is it what you
> > > > > > mean ?
> > > > > >
> > > > > >   Enable or disable the AWB.
> > > > > >
> > > > > >   When AWB is enabled, the algorithm estimates the colour temperature of
> > > > > >   the scene, and computes colour gains and the colour correction matrix
> > > > > >   automatically. The computed colour temperate, gains and correction
> > > > > >   matrix are reported in metadata. The corresponding controls are ignored
> > > > > >   if set in a request.
> > > > > >
> > > > > >   When AWB is disabled, the colour temperature, gains and correction
> > > > > >   matrix are not updated automatically and can be set manually in
> > > > > >   requests.
> > > > >
> > > > > Looks good, I'll apply that.
> > > > >
> > > > > > >
> > > > > > > +        \sa ColourCorrectionMatrix
> > > > > > >          \sa ColourGains
> > > > > > > +        \sa ColourTemperature
> > > > > > >
> > > > > > >    # AwbMode needs further attention:
> > > > > > >    # - Auto-generate max enum value.
> > > > > > > @@ -309,13 +312,24 @@ controls:
> > > > > > >          disabled.
> > > > > > >
> > > > > > >          \sa AwbEnable
> > > > > > > +        \sa ColourTemperature
> > > > > > >        size: [2]
> > > > > > >
> > > > > > >    - ColourTemperature:
> > > > > > >        type: int32_t
> > > > > > > -      description: Report the current estimate of the colour temperature, in
> > > > > > > -        kelvin, for this frame. The ColourTemperature control can only be
> > > > > > > -        returned in metadata.
> > > > > > > +      description: |
> > > > > > > +        Report the current estimate of the colour temperature, in kelvin, for
> > > > > > > +        this frame. An implementation may also allow this control to be set when
> > > > > >
> > > > > > s/also //
> > > > > >
> > > > > > > +        AWB is disabled. In that case ColourGains and the ColourCorrectionMatrix
> > > > > > > +        get set accordingly. If either ColourGains or ColourCorrectionMatrix are
> > > > > > > +        specified at the same time, they take precedence.
> > > > > >
> > > > > > maybe "they take precedence, and the ColourTemperature is ignored" ? Or,
> > > > > > if an application sets ColourTemperature and ColourGains but not
> > > > > > ColourCorrectionMatrix, do you expect the implementation to apply the
> > > > > > requested ColourGains and set ColourCorrectionMatrix based on the
> > > > > > temperature ?
> > > > >
> > > > > The latter is exactly what happens. The following table lists the
> > > > > possible options:
> > > > >
> > > > > CT -> CG(CT), CCM(CT)
> > > > > CT, CG -> CG, CCM(CT)
> > > > > CT, CCM -> CG(CT), CCM
> > > > > CT, CG, CCM -> CG, CCM
> > > >
> > > > David, is this the behaviour you would also expect for Raspberry Pi ?
> > 
> > I'm guessing the question here is really what to do if an application
> > sets both CT and CG together? The other cases seem fairly
> > uncontroversial (?).
> 
> As far as I understand, for the rkisp1, the colour gains and the CCM are
> both calculated based on the colour temperature. The case where the
> application sets CT and CG is conceptually as problematic as the case
> where it sets CT and CCM. Stefan, is that correct ?

Only CCM is set based on CT. CG is set based on the stats and these are
also used to calculate the CT. As David noted CG -> CT(CG) -> CCM(CT) is
possible. CT(CCM) is not possible afaik. So the cases are similar but
not the same.

> 
> > For us, I'm not sure it really makes much sense to supply both CT and
> > CG at once. When someone sets CG, the algorithm estimates the CT and
> > passes this to other algorithms, like lens shading and CCM. (So we
> > actually have a "CG -> CG, CT(CG), CCM(CT)" kind of case going on.)
> 
> When an application sets CG, does the algorithm estimate CT from the
> stats, or from the CG alone for RPi ? Stefan, how about your plans for
> rkisp1 ?

At the moment, we do not estimate CT from CG. But that might be worth to
do.

> 
> > When I add this new control, it will calculate CG from the calibrated
> > colour temperature curve in the camera tuning and use those, and pass
> > the CT to those other algorithms (so like the first row in the table).
> 
> That's the main use, and I think we all agree on the behaviour. It seems
> quite uncontroversial.

Yes, I think on that one we are all fine.
So CT -> CG(CT), CCM(CT) is accepted. Metadata might be an open point
here.

> 
> > I don't think I particularly want to implement cases where it takes a
> > CG value, uses them, and also a random CT which it then passes on?
> > Possibly I'd rather leave these cases (where we have both CT and CG on
> > the LHS) as either "implementation dependent" or just "undefined", and
> > recommend setting one or other.
> 
> I dislike implementation-dependent behaviours if we can avoid them, at
> least in cases that we consider valid use cases. Is there a valid use
> case for setting CT along with CG or CCM ? It sounds to me like there
> wouldn't be one for RPi. Stefan, how about you ?

To me the most prominent use case is manual WB. So the user takes a
picture of a gray patch and the application (not libcamera) calculates
wb gains based on that. If you compare to a typical digital camera I
think one would expect the following to happen: CG -> CT(CG) -> CCM(CT)

In rkisp1 we don't have that CG->CT(CG) step, but that doesn't mean we
shouldn't do it.

Looking at that with the eyes of a machine-vision user it would be
counter intuitive that the CCM suddenly changes when I change the CG.
But that can be worked around from user side, by supplying a manual CCM
in the request. Which brings me to the next point. The CCM is the only
parameter here, that is basically impossible to handcraft in an
application. So there might be use cases where I'd like to set a CCM
based on a color temperature and then hand tweak the CG.

So I would be fine if we say CG -> CG, CCM(CT(CG)). That is new to me
and I haven't look into the implementation effort yet.

CG, CT -> CG, CCM(CT) is something I'd like to have, but I don't know if
we need to force it (@David: would it be much effort on your side, just
for completeness sake?)

CCM, CT -> CG(CT), CCM also feels natural to me, but without any known
usecase. (Maybe in calibration, where you want to force a unit ccm
and check the correctness of the gains)

CT, CG, CCM -> CG, CCM  I think we can agree on that one. It is
overspecified, but the lower level controls should win.

> 
> > Does that help or just confuse further?
> 
> Let's see how the discussion progresses :-) Thank you for your input.
> 
> > > > > Do you have a nice sentence for that?
> > > >
> > > > /me checks... I have a set of French proverbs, but none of the seem very
> > > > appropriate. Sorry :-)
> > >
> > > What about "If ColourGains and ColourTemperature are specified at the
> > > same time, ColourGains takes precedence. The same applies to
> > > ColourCorrectionMatrix."?
> > >
> > > We can discuss the final wording after feedback from David.
> > >
> > > > > > > +
> > > > > > > +        The metadata will only report measured colour temperature values when
> > > > > > > +        available, even if set manually.
> > > > > >
> > > > > > I'm not sure to understand this.
> > > > >
> > > > > This is based on the comment from Kieran:
> > > > > https://patchwork.libcamera.org/patch/20771/#30590 He wanted to prepare
> > > > > for cases (RPi) where no temperature gets estimated. Only measurements
> > > > > are returned in metadata. Manually set temperature is not reflected in
> > > > > the metadata. This has the nice side effect, that you can set
> > > > > AwbEnable=false, and still get temperature estimations in the metadata.
> > > >
> > > > This means that whether or not the estimated colour temperature will be
> > > > returned in metadata will be platform-dependent. Can we avoid that ? It
> > > > makes writing portable applications much more difficult.
> > > >
> > > > My other concern is that metadata is supposed to report the setting
> > > > applied to a frame. The general rule is that, if a control can be set,
> > > > the value that has been set for a frame is reported in metadata. There
> > > > are exception for trigger-like controls. As this example clearly shows,
> > > > having multiple controls that ultimately set the same values is also
> > > > problematic from this point of view. Do we need to set a rule that
> > > > higher-level controls that get translated to lower-level controls are
> > > > never reported in metadata ?
> > > >
> > > > If we do that, then we'll have ColourTemperature as a control being
> > > > defined differently from ColourTemperature as metadata. I'm not sure I
> > > > like it much. Should we have two different controls ?
> > >
> > > We could split that to "MeasuredColourTemperature" and
> > > "AppliedColorTemperature". But there are always cases where one of them
> > > (or both) is not available (as discussed on Patch 3). I think on rkisp
> > > we could ensure that MeasuredColourTemperature is always available and
> > > contains "something" as the statistics are always available. But in the
> > > end as a user I'd prefer to know when the algorithm failed to deduce a
> > > valid colour temperature.
> 
> If the algorithm failed to estimate the colour temperature, that should
> be indicated by the absence of an estimated colour temperature in
> metadata.
> 
> David, why do you (if I understand correctly) stop estimating the colour
> temperature from the statistics in manual AWB mode ?
> 
> > > > > > > +
> > > > > > > +        \sa AwbEnable
> > > > > > > +        \sa ColourCorrectionMatrix
> > > > > > > +        \sa ColourGains
> > > > > > >
> > > > > > >    - Saturation:
> > > > > > >        type: float
> > > > > > > @@ -365,6 +379,8 @@ controls:
> > > > > > >          transformation. The 3x3 matrix is stored in conventional reading
> > > > > > >          order in an array of 9 floating point values.
> > > > > > >
> > > > > > > +        \sa AwbEnable
> > > > > > > +        \sa ColourTemperature
> > > > > > >        size: [3,3]
> > > > > > >
> > > > > > >    - ScalerCrop:
> 
> -- 
> Regards,
> 
> Laurent Pinchart

Regards,
Stefan

Looks like I forgot to reply to this.

On Mon, Sep 02, 2024 at 08:28:24AM +0100, Naushir Patuck wrote:
> On Sat, 31 Aug 2024 at 16:16, Laurent Pinchart wrote:
> > On Fri, Aug 30, 2024 at 04:31:50PM +0100, David Plowman wrote:
> > > On Fri, 30 Aug 2024 at 12:21, Stefan Klug wrote:
> > > > On Fri, Aug 30, 2024 at 01:15:55PM +0300, Laurent Pinchart wrote:
> > > > > On Fri, Aug 30, 2024 at 07:58:31AM +0200, Stefan Klug wrote:
> > > > > > On Fri, Aug 30, 2024 at 02:01:19AM +0300, Laurent Pinchart wrote:
> > > > > > > On Tue, Aug 13, 2024 at 10:44:18AM +0200, Stefan Klug wrote:
> > > > > > > > For manual control it is helpful to be able to specify a fixed colour
> > > > > > > > temperature. It also provides an easy way to apply the temperature
> > > > > > > > specific CCMs and colour gains that are contained in the tuning files.
> > > > > > > >
> > > > > > > > Document this and update the control dependencies.
> > > > > > > >
> > > > > > > > Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com>
> > > > > > > > ---
> > > > > > > >  src/libcamera/control_ids_core.yaml | 24 ++++++++++++++++++++----
> > > > > > > >  1 file changed, 20 insertions(+), 4 deletions(-)
> > > > > > > >
> > > > > > > > diff --git a/src/libcamera/control_ids_core.yaml b/src/libcamera/control_ids_core.yaml
> > > > > > > > index cf40771d3896..04dcc4af67fc 100644
> > > > > > > > --- a/src/libcamera/control_ids_core.yaml
> > > > > > > > +++ b/src/libcamera/control_ids_core.yaml
> > > > > > > > @@ -252,9 +252,12 @@ controls:
> > > > > > > >    - AwbEnable:
> > > > > > > >        type: bool
> > > > > > > >        description: |
> > > > > > > > -        Enable or disable the AWB.
> > > > > > > > +        Enable or disable the AWB. Disabling AWB stops updates to the
> > > > > > > > +        ColourGains and to the ColourCorrectionMatrix.
> > > > > > >
> > > > > > > Please split this in two paragraphs. The first paragraph is translated
> > > > > > > to a \brief doxygen command, and should be a single sentence. Same
> > > > > > > below.
> > > > > > >
> > > > > > > I would like to clarify this a bit. Here's an attempt, is it what you
> > > > > > > mean ?
> > > > > > >
> > > > > > >   Enable or disable the AWB.
> > > > > > >
> > > > > > >   When AWB is enabled, the algorithm estimates the colour temperature of
> > > > > > >   the scene, and computes colour gains and the colour correction matrix
> > > > > > >   automatically. The computed colour temperate, gains and correction
> > > > > > >   matrix are reported in metadata. The corresponding controls are ignored
> > > > > > >   if set in a request.
> > > > > > >
> > > > > > >   When AWB is disabled, the colour temperature, gains and correction
> > > > > > >   matrix are not updated automatically and can be set manually in
> > > > > > >   requests.
> > > > > >
> > > > > > Looks good, I'll apply that.
> > > > > >
> > > > > > > >
> > > > > > > > +        \sa ColourCorrectionMatrix
> > > > > > > >          \sa ColourGains
> > > > > > > > +        \sa ColourTemperature
> > > > > > > >
> > > > > > > >    # AwbMode needs further attention:
> > > > > > > >    # - Auto-generate max enum value.
> > > > > > > > @@ -309,13 +312,24 @@ controls:
> > > > > > > >          disabled.
> > > > > > > >
> > > > > > > >          \sa AwbEnable
> > > > > > > > +        \sa ColourTemperature
> > > > > > > >        size: [2]
> > > > > > > >
> > > > > > > >    - ColourTemperature:
> > > > > > > >        type: int32_t
> > > > > > > > -      description: Report the current estimate of the colour temperature, in
> > > > > > > > -        kelvin, for this frame. The ColourTemperature control can only be
> > > > > > > > -        returned in metadata.
> > > > > > > > +      description: |
> > > > > > > > +        Report the current estimate of the colour temperature, in kelvin, for
> > > > > > > > +        this frame. An implementation may also allow this control to be set when
> > > > > > >
> > > > > > > s/also //
> > > > > > >
> > > > > > > > +        AWB is disabled. In that case ColourGains and the ColourCorrectionMatrix
> > > > > > > > +        get set accordingly. If either ColourGains or ColourCorrectionMatrix are
> > > > > > > > +        specified at the same time, they take precedence.
> > > > > > >
> > > > > > > maybe "they take precedence, and the ColourTemperature is ignored" ? Or,
> > > > > > > if an application sets ColourTemperature and ColourGains but not
> > > > > > > ColourCorrectionMatrix, do you expect the implementation to apply the
> > > > > > > requested ColourGains and set ColourCorrectionMatrix based on the
> > > > > > > temperature ?
> > > > > >
> > > > > > The latter is exactly what happens. The following table lists the
> > > > > > possible options:
> > > > > >
> > > > > > CT -> CG(CT), CCM(CT)
> > > > > > CT, CG -> CG, CCM(CT)
> > > > > > CT, CCM -> CG(CT), CCM
> > > > > > CT, CG, CCM -> CG, CCM
> > > > >
> > > > > David, is this the behaviour you would also expect for Raspberry Pi ?
> > >
> > > I'm guessing the question here is really what to do if an application
> > > sets both CT and CG together? The other cases seem fairly
> > > uncontroversial (?).
> >
> > As far as I understand, for the rkisp1, the colour gains and the CCM are
> > both calculated based on the colour temperature. The case where the
> > application sets CT and CG is conceptually as problematic as the case
> > where it sets CT and CCM. Stefan, is that correct ?
> >
> > > For us, I'm not sure it really makes much sense to supply both CT and
> > > CG at once. When someone sets CG, the algorithm estimates the CT and
> > > passes this to other algorithms, like lens shading and CCM. (So we
> > > actually have a "CG -> CG, CT(CG), CCM(CT)" kind of case going on.)
> >
> > When an application sets CG, does the algorithm estimate CT from the
> > stats, or from the CG alone for RPi ? Stefan, how about your plans for
> > rkisp1 ?
> 
> When an application sets manual CGs, the algorithm estimates the CT
> from the CT-curve in the tuning directly.

I'll try to recap what we have (hopefully) agreed on so far.

OK, so in manual AWB mode, CT and CG are interchangeable, one will be
calculated from the other based on the tuning data, without taking
statistics into account. As this is a pure software implementation, if
both controls are specified, we can freely specify which one takes
precedence, and this can be applied to all platforms. I have a
preference for making the gains take precedence (as Stefan did in v5) as
they provide more precise control.

In auto AWB mode, CG and CT are both calculated by the AWB algorithm and
any value set through controls is ignored.

So far, so good ?

The next question is how to handle CCM. Auto mode is easy, CCM is
computed automatically, and any value set through controls is ignored.
In manual mode, if CCM is set in a request, its value should be applied.
What if a request contains CG or CT and no CCM ? Would CCM be computed
by the AWB algorithm (in manual mode), or its previous value retained ?

> > > When I add this new control, it will calculate CG from the calibrated
> > > colour temperature curve in the camera tuning and use those, and pass
> > > the CT to those other algorithms (so like the first row in the table).
> >
> > That's the main use, and I think we all agree on the behaviour. It seems
> > quite uncontroversial.
> >
> > > I don't think I particularly want to implement cases where it takes a
> > > CG value, uses them, and also a random CT which it then passes on?
> > > Possibly I'd rather leave these cases (where we have both CT and CG on
> > > the LHS) as either "implementation dependent" or just "undefined", and
> > > recommend setting one or other.
> >
> > I dislike implementation-dependent behaviours if we can avoid them, at
> > least in cases that we consider valid use cases. Is there a valid use
> > case for setting CT along with CG or CCM ? It sounds to me like there
> > wouldn't be one for RPi. Stefan, how about you ?
> 
> I don't think RPi has a use case that requires the CT and CGs to be both set.
> 
> > > Does that help or just confuse further?
> >
> > Let's see how the discussion progresses :-) Thank you for your input.
> >
> > > > > > Do you have a nice sentence for that?
> > > > >
> > > > > /me checks... I have a set of French proverbs, but none of the seem very
> > > > > appropriate. Sorry :-)
> > > >
> > > > What about "If ColourGains and ColourTemperature are specified at the
> > > > same time, ColourGains takes precedence. The same applies to
> > > > ColourCorrectionMatrix."?
> > > >
> > > > We can discuss the final wording after feedback from David.
> > > >
> > > > > > > > +
> > > > > > > > +        The metadata will only report measured colour temperature values when
> > > > > > > > +        available, even if set manually.
> > > > > > >
> > > > > > > I'm not sure to understand this.
> > > > > >
> > > > > > This is based on the comment from Kieran:
> > > > > > https://patchwork.libcamera.org/patch/20771/#30590 He wanted to prepare
> > > > > > for cases (RPi) where no temperature gets estimated. Only measurements
> > > > > > are returned in metadata. Manually set temperature is not reflected in
> > > > > > the metadata. This has the nice side effect, that you can set
> > > > > > AwbEnable=false, and still get temperature estimations in the metadata.
> > > > >
> > > > > This means that whether or not the estimated colour temperature will be
> > > > > returned in metadata will be platform-dependent. Can we avoid that ? It
> > > > > makes writing portable applications much more difficult.
> > > > >
> > > > > My other concern is that metadata is supposed to report the setting
> > > > > applied to a frame. The general rule is that, if a control can be set,
> > > > > the value that has been set for a frame is reported in metadata. There
> > > > > are exception for trigger-like controls. As this example clearly shows,
> > > > > having multiple controls that ultimately set the same values is also
> > > > > problematic from this point of view. Do we need to set a rule that
> > > > > higher-level controls that get translated to lower-level controls are
> > > > > never reported in metadata ?
> > > > >
> > > > > If we do that, then we'll have ColourTemperature as a control being
> > > > > defined differently from ColourTemperature as metadata. I'm not sure I
> > > > > like it much. Should we have two different controls ?
> > > >
> > > > We could split that to "MeasuredColourTemperature" and
> > > > "AppliedColorTemperature". But there are always cases where one of them
> > > > (or both) is not available (as discussed on Patch 3). I think on rkisp
> > > > we could ensure that MeasuredColourTemperature is always available and
> > > > contains "something" as the statistics are always available. But in the
> > > > end as a user I'd prefer to know when the algorithm failed to deduce a
> > > > valid colour temperature.
> >
> > If the algorithm failed to estimate the colour temperature, that should
> > be indicated by the absence of an estimated colour temperature in
> > metadata.
> >
> > David, why do you (if I understand correctly) stop estimating the colour
> > temperature from the statistics in manual AWB mode ?
> 
> I think it's to keep things consistent.  The CT-curve in the tuning
> file is taken as the canonical truth. So if manual CGs are applied,
> and assuming the users know what they are doing(!), we return a simple
> lookup without going through all the computations again.  Of course,
> this is simple enough to change in our code if the need arises.

I'm fine with that behaviour, but I would like to keep the metadata
behaviour consistent between platforms.

For auto-mode, I think we all agree that the CG, CT and CCM metadata
will report the values computed by the AWB algorithm (please wave if
you disagree).

For manual mode, we've discussed two different behaviours that apply to
CG, CT and CCM:

- Report the controls that are applied to the device. This matches the
  standard libcamera metadata behaviour.

- Let the AWB algorithm continue to process statistics, and report the
  estimated values. As far as I understand, this was requested for CT
  estimation only, not for CG or CCM estimation.

While I understand that continuous CT estimation in manual mode can be
tempting, I think it would require more discussions to specify it
unambiguously. Stefan, Kieran, do you have a use case for this now, or
is this something you considered as a nice-to-have feature ?

> > > > > > > > +
> > > > > > > > +        \sa AwbEnable
> > > > > > > > +        \sa ColourCorrectionMatrix
> > > > > > > > +        \sa ColourGains
> > > > > > > >
> > > > > > > >    - Saturation:
> > > > > > > >        type: float
> > > > > > > > @@ -365,6 +379,8 @@ controls:
> > > > > > > >          transformation. The 3x3 matrix is stored in conventional reading
> > > > > > > >          order in an array of 9 floating point values.
> > > > > > > >
> > > > > > > > +        \sa AwbEnable
> > > > > > > > +        \sa ColourTemperature
> > > > > > > >        size: [3,3]
> > > > > > > >
> > > > > > > >    - ScalerCrop:

On Mon, Sep 02, 2024 at 10:32:59AM +0200, Stefan Klug wrote:
> On Sat, Aug 31, 2024 at 06:16:10PM +0300, Laurent Pinchart wrote:
> > On Fri, Aug 30, 2024 at 04:31:50PM +0100, David Plowman wrote:
> > > On Fri, 30 Aug 2024 at 12:21, Stefan Klug wrote:
> > > > On Fri, Aug 30, 2024 at 01:15:55PM +0300, Laurent Pinchart wrote:
> > > > > On Fri, Aug 30, 2024 at 07:58:31AM +0200, Stefan Klug wrote:
> > > > > > On Fri, Aug 30, 2024 at 02:01:19AM +0300, Laurent Pinchart wrote:
> > > > > > > On Tue, Aug 13, 2024 at 10:44:18AM +0200, Stefan Klug wrote:
> > > > > > > > For manual control it is helpful to be able to specify a fixed colour
> > > > > > > > temperature. It also provides an easy way to apply the temperature
> > > > > > > > specific CCMs and colour gains that are contained in the tuning files.
> > > > > > > >
> > > > > > > > Document this and update the control dependencies.
> > > > > > > >
> > > > > > > > Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com>
> > > > > > > > ---
> > > > > > > >  src/libcamera/control_ids_core.yaml | 24 ++++++++++++++++++++----
> > > > > > > >  1 file changed, 20 insertions(+), 4 deletions(-)
> > > > > > > >
> > > > > > > > diff --git a/src/libcamera/control_ids_core.yaml b/src/libcamera/control_ids_core.yaml
> > > > > > > > index cf40771d3896..04dcc4af67fc 100644
> > > > > > > > --- a/src/libcamera/control_ids_core.yaml
> > > > > > > > +++ b/src/libcamera/control_ids_core.yaml
> > > > > > > > @@ -252,9 +252,12 @@ controls:
> > > > > > > >    - AwbEnable:
> > > > > > > >        type: bool
> > > > > > > >        description: |
> > > > > > > > -        Enable or disable the AWB.
> > > > > > > > +        Enable or disable the AWB. Disabling AWB stops updates to the
> > > > > > > > +        ColourGains and to the ColourCorrectionMatrix.
> > > > > > >
> > > > > > > Please split this in two paragraphs. The first paragraph is translated
> > > > > > > to a \brief doxygen command, and should be a single sentence. Same
> > > > > > > below.
> > > > > > >
> > > > > > > I would like to clarify this a bit. Here's an attempt, is it what you
> > > > > > > mean ?
> > > > > > >
> > > > > > >   Enable or disable the AWB.
> > > > > > >
> > > > > > >   When AWB is enabled, the algorithm estimates the colour temperature of
> > > > > > >   the scene, and computes colour gains and the colour correction matrix
> > > > > > >   automatically. The computed colour temperate, gains and correction
> > > > > > >   matrix are reported in metadata. The corresponding controls are ignored
> > > > > > >   if set in a request.
> > > > > > >
> > > > > > >   When AWB is disabled, the colour temperature, gains and correction
> > > > > > >   matrix are not updated automatically and can be set manually in
> > > > > > >   requests.
> > > > > >
> > > > > > Looks good, I'll apply that.
> > > > > >
> > > > > > > >
> > > > > > > > +        \sa ColourCorrectionMatrix
> > > > > > > >          \sa ColourGains
> > > > > > > > +        \sa ColourTemperature
> > > > > > > >
> > > > > > > >    # AwbMode needs further attention:
> > > > > > > >    # - Auto-generate max enum value.
> > > > > > > > @@ -309,13 +312,24 @@ controls:
> > > > > > > >          disabled.
> > > > > > > >
> > > > > > > >          \sa AwbEnable
> > > > > > > > +        \sa ColourTemperature
> > > > > > > >        size: [2]
> > > > > > > >
> > > > > > > >    - ColourTemperature:
> > > > > > > >        type: int32_t
> > > > > > > > -      description: Report the current estimate of the colour temperature, in
> > > > > > > > -        kelvin, for this frame. The ColourTemperature control can only be
> > > > > > > > -        returned in metadata.
> > > > > > > > +      description: |
> > > > > > > > +        Report the current estimate of the colour temperature, in kelvin, for
> > > > > > > > +        this frame. An implementation may also allow this control to be set when
> > > > > > >
> > > > > > > s/also //
> > > > > > >
> > > > > > > > +        AWB is disabled. In that case ColourGains and the ColourCorrectionMatrix
> > > > > > > > +        get set accordingly. If either ColourGains or ColourCorrectionMatrix are
> > > > > > > > +        specified at the same time, they take precedence.
> > > > > > >
> > > > > > > maybe "they take precedence, and the ColourTemperature is ignored" ? Or,
> > > > > > > if an application sets ColourTemperature and ColourGains but not
> > > > > > > ColourCorrectionMatrix, do you expect the implementation to apply the
> > > > > > > requested ColourGains and set ColourCorrectionMatrix based on the
> > > > > > > temperature ?
> > > > > >
> > > > > > The latter is exactly what happens. The following table lists the
> > > > > > possible options:
> > > > > >
> > > > > > CT -> CG(CT), CCM(CT)
> > > > > > CT, CG -> CG, CCM(CT)
> > > > > > CT, CCM -> CG(CT), CCM
> > > > > > CT, CG, CCM -> CG, CCM
> > > > >
> > > > > David, is this the behaviour you would also expect for Raspberry Pi ?
> > > 
> > > I'm guessing the question here is really what to do if an application
> > > sets both CT and CG together? The other cases seem fairly
> > > uncontroversial (?).
> > 
> > As far as I understand, for the rkisp1, the colour gains and the CCM are
> > both calculated based on the colour temperature. The case where the
> > application sets CT and CG is conceptually as problematic as the case
> > where it sets CT and CCM. Stefan, is that correct ?
> 
> Only CCM is set based on CT. CG is set based on the stats and these are
> also used to calculate the CT. As David noted CG -> CT(CG) -> CCM(CT) is
> possible. CT(CCM) is not possible afaik. So the cases are similar but
> not the same.
> 
> > > For us, I'm not sure it really makes much sense to supply both CT and
> > > CG at once. When someone sets CG, the algorithm estimates the CT and
> > > passes this to other algorithms, like lens shading and CCM. (So we
> > > actually have a "CG -> CG, CT(CG), CCM(CT)" kind of case going on.)
> > 
> > When an application sets CG, does the algorithm estimate CT from the
> > stats, or from the CG alone for RPi ? Stefan, how about your plans for
> > rkisp1 ?
> 
> At the moment, we do not estimate CT from CG. But that might be worth to
> do.
> 
> > > When I add this new control, it will calculate CG from the calibrated
> > > colour temperature curve in the camera tuning and use those, and pass
> > > the CT to those other algorithms (so like the first row in the table).
> > 
> > That's the main use, and I think we all agree on the behaviour. It seems
> > quite uncontroversial.
> 
> Yes, I think on that one we are all fine.
> So CT -> CG(CT), CCM(CT) is accepted. Metadata might be an open point
> here.
> 
> > > I don't think I particularly want to implement cases where it takes a
> > > CG value, uses them, and also a random CT which it then passes on?
> > > Possibly I'd rather leave these cases (where we have both CT and CG on
> > > the LHS) as either "implementation dependent" or just "undefined", and
> > > recommend setting one or other.
> > 
> > I dislike implementation-dependent behaviours if we can avoid them, at
> > least in cases that we consider valid use cases. Is there a valid use
> > case for setting CT along with CG or CCM ? It sounds to me like there
> > wouldn't be one for RPi. Stefan, how about you ?
> 
> To me the most prominent use case is manual WB. So the user takes a
> picture of a gray patch and the application (not libcamera) calculates
> wb gains based on that. If you compare to a typical digital camera I
> think one would expect the following to happen: CG -> CT(CG) -> CCM(CT)
> 
> In rkisp1 we don't have that CG->CT(CG) step, but that doesn't mean we
> shouldn't do it.

To make sure I understand you correctly, what you're proposing is

- AWB disabled
- Application sets CG
- IPA computes CT(CG) and CCM(CG,CT), and applies CCM

Note that I wrote CCM(CG,CT) to let implementations decide how to
compute CCM. Whether they use CG, CT or both is an implementation
detail. Statistics are *not* used to compute either CT or CCM, they are
completely ignored.

Is that right ? That seems easy to specify and implement, so I'm fine
with it. The use case with CG and CT swapped would be

- AWB disabled
- Application sets CT
- IPA computes CG(CT) and CCM(CG,CT), and applies CCM

can easily be supported too, and the two options don't conflict with
each other as they're user-selectable (by setting either CG or CT).

> Looking at that with the eyes of a machine-vision user it would be
> counter intuitive that the CCM suddenly changes when I change the CG.

Could you elaborate on why that is the case ?

> But that can be worked around from user side, by supplying a manual CCM
> in the request. Which brings me to the next point. The CCM is the only
> parameter here, that is basically impossible to handcraft in an
> application. So there might be use cases where I'd like to set a CCM
> based on a color temperature and then hand tweak the CG.

To do so, you would need to set the CG, wait until it gets applied,
retrieved the CCM from the metadata, and then change the CG while
specifying the CCM in the same request. Is that what you have in mind ?

> So I would be fine if we say CG -> CG, CCM(CT(CG)). That is new to me
> and I haven't look into the implementation effort yet.
>
> CG, CT -> CG, CCM(CT) is something I'd like to have, but I don't know if
> we need to force it (@David: would it be much effort on your side, just
> for completeness sake?)

How would we document that ? We can't say anymore that CG takes
precedence over CT. This would require documenting precisely how the
different values are computed from each other in all cases, and would
limit options for IPA modules. I fear we may corner ourselves.

> CCM, CT -> CG(CT), CCM also feels natural to me, but without any known
> usecase. (Maybe in calibration, where you want to force a unit ccm
> and check the correctness of the gains)

I'm fine with this, we can document that CCM, when specified, overrides
any computed value.

> CT, CG, CCM -> CG, CCM  I think we can agree on that one. It is
> overspecified, but the lower level controls should win.

Yes, this is fine.

> > > Does that help or just confuse further?
> > 
> > Let's see how the discussion progresses :-) Thank you for your input.
> > 
> > > > > > Do you have a nice sentence for that?
> > > > >
> > > > > /me checks... I have a set of French proverbs, but none of the seem very
> > > > > appropriate. Sorry :-)
> > > >
> > > > What about "If ColourGains and ColourTemperature are specified at the
> > > > same time, ColourGains takes precedence. The same applies to
> > > > ColourCorrectionMatrix."?
> > > >
> > > > We can discuss the final wording after feedback from David.
> > > >
> > > > > > > > +
> > > > > > > > +        The metadata will only report measured colour temperature values when
> > > > > > > > +        available, even if set manually.
> > > > > > >
> > > > > > > I'm not sure to understand this.
> > > > > >
> > > > > > This is based on the comment from Kieran:
> > > > > > https://patchwork.libcamera.org/patch/20771/#30590 He wanted to prepare
> > > > > > for cases (RPi) where no temperature gets estimated. Only measurements
> > > > > > are returned in metadata. Manually set temperature is not reflected in
> > > > > > the metadata. This has the nice side effect, that you can set
> > > > > > AwbEnable=false, and still get temperature estimations in the metadata.
> > > > >
> > > > > This means that whether or not the estimated colour temperature will be
> > > > > returned in metadata will be platform-dependent. Can we avoid that ? It
> > > > > makes writing portable applications much more difficult.
> > > > >
> > > > > My other concern is that metadata is supposed to report the setting
> > > > > applied to a frame. The general rule is that, if a control can be set,
> > > > > the value that has been set for a frame is reported in metadata. There
> > > > > are exception for trigger-like controls. As this example clearly shows,
> > > > > having multiple controls that ultimately set the same values is also
> > > > > problematic from this point of view. Do we need to set a rule that
> > > > > higher-level controls that get translated to lower-level controls are
> > > > > never reported in metadata ?
> > > > >
> > > > > If we do that, then we'll have ColourTemperature as a control being
> > > > > defined differently from ColourTemperature as metadata. I'm not sure I
> > > > > like it much. Should we have two different controls ?
> > > >
> > > > We could split that to "MeasuredColourTemperature" and
> > > > "AppliedColorTemperature". But there are always cases where one of them
> > > > (or both) is not available (as discussed on Patch 3). I think on rkisp
> > > > we could ensure that MeasuredColourTemperature is always available and
> > > > contains "something" as the statistics are always available. But in the
> > > > end as a user I'd prefer to know when the algorithm failed to deduce a
> > > > valid colour temperature.
> > 
> > If the algorithm failed to estimate the colour temperature, that should
> > be indicated by the absence of an estimated colour temperature in
> > metadata.
> > 
> > David, why do you (if I understand correctly) stop estimating the colour
> > temperature from the statistics in manual AWB mode ?
> > 
> > > > > > > > +
> > > > > > > > +        \sa AwbEnable
> > > > > > > > +        \sa ColourCorrectionMatrix
> > > > > > > > +        \sa ColourGains
> > > > > > > >
> > > > > > > >    - Saturation:
> > > > > > > >        type: float
> > > > > > > > @@ -365,6 +379,8 @@ controls:
> > > > > > > >          transformation. The 3x3 matrix is stored in conventional reading
> > > > > > > >          order in an array of 9 floating point values.
> > > > > > > >
> > > > > > > > +        \sa AwbEnable
> > > > > > > > +        \sa ColourTemperature
> > > > > > > >        size: [3,3]
> > > > > > > >
> > > > > > > >    - ScalerCrop:

Hi Laurent,

On Mon, Dec 09, 2024 at 03:02:09AM +0200, Laurent Pinchart wrote:
> Looks like I forgot to reply to this.
> 
> On Mon, Sep 02, 2024 at 08:28:24AM +0100, Naushir Patuck wrote:
> > On Sat, 31 Aug 2024 at 16:16, Laurent Pinchart wrote:
> > > On Fri, Aug 30, 2024 at 04:31:50PM +0100, David Plowman wrote:
> > > > On Fri, 30 Aug 2024 at 12:21, Stefan Klug wrote:
> > > > > On Fri, Aug 30, 2024 at 01:15:55PM +0300, Laurent Pinchart wrote:
> > > > > > On Fri, Aug 30, 2024 at 07:58:31AM +0200, Stefan Klug wrote:
> > > > > > > On Fri, Aug 30, 2024 at 02:01:19AM +0300, Laurent Pinchart wrote:
> > > > > > > > On Tue, Aug 13, 2024 at 10:44:18AM +0200, Stefan Klug wrote:
> > > > > > > > > For manual control it is helpful to be able to specify a fixed colour
> > > > > > > > > temperature. It also provides an easy way to apply the temperature
> > > > > > > > > specific CCMs and colour gains that are contained in the tuning files.
> > > > > > > > >
> > > > > > > > > Document this and update the control dependencies.
> > > > > > > > >
> > > > > > > > > Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com>
> > > > > > > > > ---
> > > > > > > > >  src/libcamera/control_ids_core.yaml | 24 ++++++++++++++++++++----
> > > > > > > > >  1 file changed, 20 insertions(+), 4 deletions(-)
> > > > > > > > >
> > > > > > > > > diff --git a/src/libcamera/control_ids_core.yaml b/src/libcamera/control_ids_core.yaml
> > > > > > > > > index cf40771d3896..04dcc4af67fc 100644
> > > > > > > > > --- a/src/libcamera/control_ids_core.yaml
> > > > > > > > > +++ b/src/libcamera/control_ids_core.yaml
> > > > > > > > > @@ -252,9 +252,12 @@ controls:
> > > > > > > > >    - AwbEnable:
> > > > > > > > >        type: bool
> > > > > > > > >        description: |
> > > > > > > > > -        Enable or disable the AWB.
> > > > > > > > > +        Enable or disable the AWB. Disabling AWB stops updates to the
> > > > > > > > > +        ColourGains and to the ColourCorrectionMatrix.
> > > > > > > >
> > > > > > > > Please split this in two paragraphs. The first paragraph is translated
> > > > > > > > to a \brief doxygen command, and should be a single sentence. Same
> > > > > > > > below.
> > > > > > > >
> > > > > > > > I would like to clarify this a bit. Here's an attempt, is it what you
> > > > > > > > mean ?
> > > > > > > >
> > > > > > > >   Enable or disable the AWB.
> > > > > > > >
> > > > > > > >   When AWB is enabled, the algorithm estimates the colour temperature of
> > > > > > > >   the scene, and computes colour gains and the colour correction matrix
> > > > > > > >   automatically. The computed colour temperate, gains and correction
> > > > > > > >   matrix are reported in metadata. The corresponding controls are ignored
> > > > > > > >   if set in a request.
> > > > > > > >
> > > > > > > >   When AWB is disabled, the colour temperature, gains and correction
> > > > > > > >   matrix are not updated automatically and can be set manually in
> > > > > > > >   requests.
> > > > > > >
> > > > > > > Looks good, I'll apply that.
> > > > > > >
> > > > > > > > >
> > > > > > > > > +        \sa ColourCorrectionMatrix
> > > > > > > > >          \sa ColourGains
> > > > > > > > > +        \sa ColourTemperature
> > > > > > > > >
> > > > > > > > >    # AwbMode needs further attention:
> > > > > > > > >    # - Auto-generate max enum value.
> > > > > > > > > @@ -309,13 +312,24 @@ controls:
> > > > > > > > >          disabled.
> > > > > > > > >
> > > > > > > > >          \sa AwbEnable
> > > > > > > > > +        \sa ColourTemperature
> > > > > > > > >        size: [2]
> > > > > > > > >
> > > > > > > > >    - ColourTemperature:
> > > > > > > > >        type: int32_t
> > > > > > > > > -      description: Report the current estimate of the colour temperature, in
> > > > > > > > > -        kelvin, for this frame. The ColourTemperature control can only be
> > > > > > > > > -        returned in metadata.
> > > > > > > > > +      description: |
> > > > > > > > > +        Report the current estimate of the colour temperature, in kelvin, for
> > > > > > > > > +        this frame. An implementation may also allow this control to be set when
> > > > > > > >
> > > > > > > > s/also //
> > > > > > > >
> > > > > > > > > +        AWB is disabled. In that case ColourGains and the ColourCorrectionMatrix
> > > > > > > > > +        get set accordingly. If either ColourGains or ColourCorrectionMatrix are
> > > > > > > > > +        specified at the same time, they take precedence.
> > > > > > > >
> > > > > > > > maybe "they take precedence, and the ColourTemperature is ignored" ? Or,
> > > > > > > > if an application sets ColourTemperature and ColourGains but not
> > > > > > > > ColourCorrectionMatrix, do you expect the implementation to apply the
> > > > > > > > requested ColourGains and set ColourCorrectionMatrix based on the
> > > > > > > > temperature ?
> > > > > > >
> > > > > > > The latter is exactly what happens. The following table lists the
> > > > > > > possible options:
> > > > > > >
> > > > > > > CT -> CG(CT), CCM(CT)
> > > > > > > CT, CG -> CG, CCM(CT)
> > > > > > > CT, CCM -> CG(CT), CCM
> > > > > > > CT, CG, CCM -> CG, CCM
> > > > > >
> > > > > > David, is this the behaviour you would also expect for Raspberry Pi ?
> > > >
> > > > I'm guessing the question here is really what to do if an application
> > > > sets both CT and CG together? The other cases seem fairly
> > > > uncontroversial (?).
> > >
> > > As far as I understand, for the rkisp1, the colour gains and the CCM are
> > > both calculated based on the colour temperature. The case where the
> > > application sets CT and CG is conceptually as problematic as the case
> > > where it sets CT and CCM. Stefan, is that correct ?
> > >
> > > > For us, I'm not sure it really makes much sense to supply both CT and
> > > > CG at once. When someone sets CG, the algorithm estimates the CT and
> > > > passes this to other algorithms, like lens shading and CCM. (So we
> > > > actually have a "CG -> CG, CT(CG), CCM(CT)" kind of case going on.)
> > >
> > > When an application sets CG, does the algorithm estimate CT from the
> > > stats, or from the CG alone for RPi ? Stefan, how about your plans for
> > > rkisp1 ?
> > 
> > When an application sets manual CGs, the algorithm estimates the CT
> > from the CT-curve in the tuning directly.
> 
> I'll try to recap what we have (hopefully) agreed on so far.
> 
> OK, so in manual AWB mode, CT and CG are interchangeable, one will be
> calculated from the other based on the tuning data, without taking
> statistics into account. As this is a pure software implementation, if
> both controls are specified, we can freely specify which one takes
> precedence, and this can be applied to all platforms. I have a
> preference for making the gains take precedence (as Stefan did in v5) as
> they provide more precise control.

As written in the next paragraph, I propose for no precedence between CG
and CT at all as we would unnecessarily limit our options.

> 
> In auto AWB mode, CG and CT are both calculated by the AWB algorithm and
> any value set through controls is ignored.
> 
> So far, so good ?
> 
> The next question is how to handle CCM. Auto mode is easy, CCM is
> computed automatically, and any value set through controls is ignored.
> In manual mode, if CCM is set in a request, its value should be applied.
> What if a request contains CG or CT and no CCM ? Would CCM be computed
> by the AWB algorithm (in manual mode), or its previous value retained ?
> 

I prepared a new update to the controls documentation, that I'll post
shortly. The proposal there is (for manual mode only):

- CG updates CT if CT is not set.
- CT updates CG if CG is not set.
- CT updates CCM if CCM is not set (Which could be triggered by the CG ->
  CT -> CCM chain)

That seems to be easiest to explain at the moment captures most use
cases.

> > > > When I add this new control, it will calculate CG from the calibrated
> > > > colour temperature curve in the camera tuning and use those, and pass
> > > > the CT to those other algorithms (so like the first row in the table).
> > >
> > > That's the main use, and I think we all agree on the behaviour. It seems
> > > quite uncontroversial.
> > >
> > > > I don't think I particularly want to implement cases where it takes a
> > > > CG value, uses them, and also a random CT which it then passes on?
> > > > Possibly I'd rather leave these cases (where we have both CT and CG on
> > > > the LHS) as either "implementation dependent" or just "undefined", and
> > > > recommend setting one or other.
> > >
> > > I dislike implementation-dependent behaviours if we can avoid them, at
> > > least in cases that we consider valid use cases. Is there a valid use
> > > case for setting CT along with CG or CCM ? It sounds to me like there
> > > wouldn't be one for RPi. Stefan, how about you ?
> > 
> > I don't think RPi has a use case that requires the CT and CGs to be both set.
> > 
> > > > Does that help or just confuse further?
> > >
> > > Let's see how the discussion progresses :-) Thank you for your input.
> > >
> > > > > > > Do you have a nice sentence for that?
> > > > > >
> > > > > > /me checks... I have a set of French proverbs, but none of the seem very
> > > > > > appropriate. Sorry :-)
> > > > >
> > > > > What about "If ColourGains and ColourTemperature are specified at the
> > > > > same time, ColourGains takes precedence. The same applies to
> > > > > ColourCorrectionMatrix."?
> > > > >
> > > > > We can discuss the final wording after feedback from David.
> > > > >
> > > > > > > > > +
> > > > > > > > > +        The metadata will only report measured colour temperature values when
> > > > > > > > > +        available, even if set manually.
> > > > > > > >
> > > > > > > > I'm not sure to understand this.
> > > > > > >
> > > > > > > This is based on the comment from Kieran:
> > > > > > > https://patchwork.libcamera.org/patch/20771/#30590 He wanted to prepare
> > > > > > > for cases (RPi) where no temperature gets estimated. Only measurements
> > > > > > > are returned in metadata. Manually set temperature is not reflected in
> > > > > > > the metadata. This has the nice side effect, that you can set
> > > > > > > AwbEnable=false, and still get temperature estimations in the metadata.
> > > > > >
> > > > > > This means that whether or not the estimated colour temperature will be
> > > > > > returned in metadata will be platform-dependent. Can we avoid that ? It
> > > > > > makes writing portable applications much more difficult.
> > > > > >
> > > > > > My other concern is that metadata is supposed to report the setting
> > > > > > applied to a frame. The general rule is that, if a control can be set,
> > > > > > the value that has been set for a frame is reported in metadata. There
> > > > > > are exception for trigger-like controls. As this example clearly shows,
> > > > > > having multiple controls that ultimately set the same values is also
> > > > > > problematic from this point of view. Do we need to set a rule that
> > > > > > higher-level controls that get translated to lower-level controls are
> > > > > > never reported in metadata ?
> > > > > >
> > > > > > If we do that, then we'll have ColourTemperature as a control being
> > > > > > defined differently from ColourTemperature as metadata. I'm not sure I
> > > > > > like it much. Should we have two different controls ?
> > > > >
> > > > > We could split that to "MeasuredColourTemperature" and
> > > > > "AppliedColorTemperature". But there are always cases where one of them
> > > > > (or both) is not available (as discussed on Patch 3). I think on rkisp
> > > > > we could ensure that MeasuredColourTemperature is always available and
> > > > > contains "something" as the statistics are always available. But in the
> > > > > end as a user I'd prefer to know when the algorithm failed to deduce a
> > > > > valid colour temperature.
> > >
> > > If the algorithm failed to estimate the colour temperature, that should
> > > be indicated by the absence of an estimated colour temperature in
> > > metadata.
> > >
> > > David, why do you (if I understand correctly) stop estimating the colour
> > > temperature from the statistics in manual AWB mode ?
> > 
> > I think it's to keep things consistent.  The CT-curve in the tuning
> > file is taken as the canonical truth. So if manual CGs are applied,
> > and assuming the users know what they are doing(!), we return a simple
> > lookup without going through all the computations again.  Of course,
> > this is simple enough to change in our code if the need arises.
> 
> I'm fine with that behaviour, but I would like to keep the metadata
> behaviour consistent between platforms.
> 
> For auto-mode, I think we all agree that the CG, CT and CCM metadata
> will report the values computed by the AWB algorithm (please wave if
> you disagree).
> 
> For manual mode, we've discussed two different behaviours that apply to
> CG, CT and CCM:
> 
> - Report the controls that are applied to the device. This matches the
>   standard libcamera metadata behaviour.
> 
> - Let the AWB algorithm continue to process statistics, and report the
>   estimated values. As far as I understand, this was requested for CT
>   estimation only, not for CG or CCM estimation.
> 
> While I understand that continuous CT estimation in manual mode can be
> tempting, I think it would require more discussions to specify it
> unambiguously. Stefan, Kieran, do you have a use case for this now, or
> is this something you considered as a nice-to-have feature ?

The discussion roughly went as follows:

There are valid cases for both colour temperatures. The one from the
statistics engine (measuredTemp) would be very useful to do any manual
regulation (outside of libcamera). The one used in the ISP for
processing the frame at hand (usedTemp) is useful to store in image
metadata or similar things. But for none of them there is a hard use
case.

The issue with usedTemp is that it is not well defined in manual mode.
At the time this was discussed we also had no way on rkisp1 to map from
CG to CT. As you lean towards that value I propose the following:

CT: usedTemp = CT, correct
CG: usedTemp = CT(CG), correct (now possible on rkisp1 also)
CT,CG: usedTemp = CT, incorrect because CG not taken into account but best
effort
CCM: usedTemp is unchanged, incorrect but best effort

I think we can live with that incorrectness as it only affects corner
cases.

For the measuredTemp we can easily introduce a MeasuredColourTemperature
metadata at a later stage.

Regards,
Stefan

> 
> > > > > > > > > +
> > > > > > > > > +        \sa AwbEnable
> > > > > > > > > +        \sa ColourCorrectionMatrix
> > > > > > > > > +        \sa ColourGains
> > > > > > > > >
> > > > > > > > >    - Saturation:
> > > > > > > > >        type: float
> > > > > > > > > @@ -365,6 +379,8 @@ controls:
> > > > > > > > >          transformation. The 3x3 matrix is stored in conventional reading
> > > > > > > > >          order in an array of 9 floating point values.
> > > > > > > > >
> > > > > > > > > +        \sa AwbEnable
> > > > > > > > > +        \sa ColourTemperature
> > > > > > > > >        size: [3,3]
> > > > > > > > >
> > > > > > > > >    - ScalerCrop:
> 
> -- 
> Regards,
> 
> Laurent Pinchart

Hi Laurent,

On Mon, Dec 09, 2024 at 03:47:29AM +0200, Laurent Pinchart wrote:
> On Mon, Sep 02, 2024 at 10:32:59AM +0200, Stefan Klug wrote:
> > On Sat, Aug 31, 2024 at 06:16:10PM +0300, Laurent Pinchart wrote:
> > > On Fri, Aug 30, 2024 at 04:31:50PM +0100, David Plowman wrote:
> > > > On Fri, 30 Aug 2024 at 12:21, Stefan Klug wrote:
> > > > > On Fri, Aug 30, 2024 at 01:15:55PM +0300, Laurent Pinchart wrote:
> > > > > > On Fri, Aug 30, 2024 at 07:58:31AM +0200, Stefan Klug wrote:
> > > > > > > On Fri, Aug 30, 2024 at 02:01:19AM +0300, Laurent Pinchart wrote:
> > > > > > > > On Tue, Aug 13, 2024 at 10:44:18AM +0200, Stefan Klug wrote:
> > > > > > > > > For manual control it is helpful to be able to specify a fixed colour
> > > > > > > > > temperature. It also provides an easy way to apply the temperature
> > > > > > > > > specific CCMs and colour gains that are contained in the tuning files.
> > > > > > > > >
> > > > > > > > > Document this and update the control dependencies.
> > > > > > > > >
> > > > > > > > > Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com>
> > > > > > > > > ---
> > > > > > > > >  src/libcamera/control_ids_core.yaml | 24 ++++++++++++++++++++----
> > > > > > > > >  1 file changed, 20 insertions(+), 4 deletions(-)
> > > > > > > > >
> > > > > > > > > diff --git a/src/libcamera/control_ids_core.yaml b/src/libcamera/control_ids_core.yaml
> > > > > > > > > index cf40771d3896..04dcc4af67fc 100644
> > > > > > > > > --- a/src/libcamera/control_ids_core.yaml
> > > > > > > > > +++ b/src/libcamera/control_ids_core.yaml
> > > > > > > > > @@ -252,9 +252,12 @@ controls:
> > > > > > > > >    - AwbEnable:
> > > > > > > > >        type: bool
> > > > > > > > >        description: |
> > > > > > > > > -        Enable or disable the AWB.
> > > > > > > > > +        Enable or disable the AWB. Disabling AWB stops updates to the
> > > > > > > > > +        ColourGains and to the ColourCorrectionMatrix.
> > > > > > > >
> > > > > > > > Please split this in two paragraphs. The first paragraph is translated
> > > > > > > > to a \brief doxygen command, and should be a single sentence. Same
> > > > > > > > below.
> > > > > > > >
> > > > > > > > I would like to clarify this a bit. Here's an attempt, is it what you
> > > > > > > > mean ?
> > > > > > > >
> > > > > > > >   Enable or disable the AWB.
> > > > > > > >
> > > > > > > >   When AWB is enabled, the algorithm estimates the colour temperature of
> > > > > > > >   the scene, and computes colour gains and the colour correction matrix
> > > > > > > >   automatically. The computed colour temperate, gains and correction
> > > > > > > >   matrix are reported in metadata. The corresponding controls are ignored
> > > > > > > >   if set in a request.
> > > > > > > >
> > > > > > > >   When AWB is disabled, the colour temperature, gains and correction
> > > > > > > >   matrix are not updated automatically and can be set manually in
> > > > > > > >   requests.
> > > > > > >
> > > > > > > Looks good, I'll apply that.
> > > > > > >
> > > > > > > > >
> > > > > > > > > +        \sa ColourCorrectionMatrix
> > > > > > > > >          \sa ColourGains
> > > > > > > > > +        \sa ColourTemperature
> > > > > > > > >
> > > > > > > > >    # AwbMode needs further attention:
> > > > > > > > >    # - Auto-generate max enum value.
> > > > > > > > > @@ -309,13 +312,24 @@ controls:
> > > > > > > > >          disabled.
> > > > > > > > >
> > > > > > > > >          \sa AwbEnable
> > > > > > > > > +        \sa ColourTemperature
> > > > > > > > >        size: [2]
> > > > > > > > >
> > > > > > > > >    - ColourTemperature:
> > > > > > > > >        type: int32_t
> > > > > > > > > -      description: Report the current estimate of the colour temperature, in
> > > > > > > > > -        kelvin, for this frame. The ColourTemperature control can only be
> > > > > > > > > -        returned in metadata.
> > > > > > > > > +      description: |
> > > > > > > > > +        Report the current estimate of the colour temperature, in kelvin, for
> > > > > > > > > +        this frame. An implementation may also allow this control to be set when
> > > > > > > >
> > > > > > > > s/also //
> > > > > > > >
> > > > > > > > > +        AWB is disabled. In that case ColourGains and the ColourCorrectionMatrix
> > > > > > > > > +        get set accordingly. If either ColourGains or ColourCorrectionMatrix are
> > > > > > > > > +        specified at the same time, they take precedence.
> > > > > > > >
> > > > > > > > maybe "they take precedence, and the ColourTemperature is ignored" ? Or,
> > > > > > > > if an application sets ColourTemperature and ColourGains but not
> > > > > > > > ColourCorrectionMatrix, do you expect the implementation to apply the
> > > > > > > > requested ColourGains and set ColourCorrectionMatrix based on the
> > > > > > > > temperature ?
> > > > > > >
> > > > > > > The latter is exactly what happens. The following table lists the
> > > > > > > possible options:
> > > > > > >
> > > > > > > CT -> CG(CT), CCM(CT)
> > > > > > > CT, CG -> CG, CCM(CT)
> > > > > > > CT, CCM -> CG(CT), CCM
> > > > > > > CT, CG, CCM -> CG, CCM
> > > > > >
> > > > > > David, is this the behaviour you would also expect for Raspberry Pi ?
> > > > 
> > > > I'm guessing the question here is really what to do if an application
> > > > sets both CT and CG together? The other cases seem fairly
> > > > uncontroversial (?).
> > > 
> > > As far as I understand, for the rkisp1, the colour gains and the CCM are
> > > both calculated based on the colour temperature. The case where the
> > > application sets CT and CG is conceptually as problematic as the case
> > > where it sets CT and CCM. Stefan, is that correct ?
> > 
> > Only CCM is set based on CT. CG is set based on the stats and these are
> > also used to calculate the CT. As David noted CG -> CT(CG) -> CCM(CT) is
> > possible. CT(CCM) is not possible afaik. So the cases are similar but
> > not the same.
> > 
> > > > For us, I'm not sure it really makes much sense to supply both CT and
> > > > CG at once. When someone sets CG, the algorithm estimates the CT and
> > > > passes this to other algorithms, like lens shading and CCM. (So we
> > > > actually have a "CG -> CG, CT(CG), CCM(CT)" kind of case going on.)
> > > 
> > > When an application sets CG, does the algorithm estimate CT from the
> > > stats, or from the CG alone for RPi ? Stefan, how about your plans for
> > > rkisp1 ?
> > 
> > At the moment, we do not estimate CT from CG. But that might be worth to
> > do.
> > 
> > > > When I add this new control, it will calculate CG from the calibrated
> > > > colour temperature curve in the camera tuning and use those, and pass
> > > > the CT to those other algorithms (so like the first row in the table).
> > > 
> > > That's the main use, and I think we all agree on the behaviour. It seems
> > > quite uncontroversial.
> > 
> > Yes, I think on that one we are all fine.
> > So CT -> CG(CT), CCM(CT) is accepted. Metadata might be an open point
> > here.
> > 
> > > > I don't think I particularly want to implement cases where it takes a
> > > > CG value, uses them, and also a random CT which it then passes on?
> > > > Possibly I'd rather leave these cases (where we have both CT and CG on
> > > > the LHS) as either "implementation dependent" or just "undefined", and
> > > > recommend setting one or other.
> > > 
> > > I dislike implementation-dependent behaviours if we can avoid them, at
> > > least in cases that we consider valid use cases. Is there a valid use
> > > case for setting CT along with CG or CCM ? It sounds to me like there
> > > wouldn't be one for RPi. Stefan, how about you ?
> > 
> > To me the most prominent use case is manual WB. So the user takes a
> > picture of a gray patch and the application (not libcamera) calculates
> > wb gains based on that. If you compare to a typical digital camera I
> > think one would expect the following to happen: CG -> CT(CG) -> CCM(CT)
> > 
> > In rkisp1 we don't have that CG->CT(CG) step, but that doesn't mean we
> > shouldn't do it.
> 
> To make sure I understand you correctly, what you're proposing is
> 
> - AWB disabled
> - Application sets CG
> - IPA computes CT(CG) and CCM(CG,CT), and applies CCM
> 
> Note that I wrote CCM(CG,CT) to let implementations decide how to
> compute CCM. Whether they use CG, CT or both is an implementation
> detail. Statistics are *not* used to compute either CT or CCM, they are
> completely ignored.
> 
> Is that right ? That seems easy to specify and implement, so I'm fine
> with it. The use case with CG and CT swapped would be
> 
> - AWB disabled
> - Application sets CT
> - IPA computes CG(CT) and CCM(CG,CT), and applies CCM
> 
> can easily be supported too, and the two options don't conflict with
> each other as they're user-selectable (by setting either CG or CT).
> 
> > Looking at that with the eyes of a machine-vision user it would be
> > counter intuitive that the CCM suddenly changes when I change the CG.
> 
> Could you elaborate on why that is the case ?

I guess it stems from the model of MV cameras. In SFNC there is no
notion of colour temperature at all, but colour gains and ccm. ccm for
colour space transform and cg for the white balance. Both can be
described using calibration and a colour temperature but are otherwise
completely independent. As these cameras tend to have no ct estimation
at all and only do grey world model white balance, this is also not
needed. So I'm used to loading a ccm for a given light source (in our
case by specifying a CT) and then adjust the cg to reproduce grays as
grays. But that is quit theoretical. 
(See also https://docs.baslerweb.com/light-source-preset )

> 
> > But that can be worked around from user side, by supplying a manual CCM
> > in the request. Which brings me to the next point. The CCM is the only
> > parameter here, that is basically impossible to handcraft in an
> > application. So there might be use cases where I'd like to set a CCM
> > based on a color temperature and then hand tweak the CG.
> 
> To do so, you would need to set the CG, wait until it gets applied,
> retrieved the CCM from the metadata, and then change the CG while
> specifying the CCM in the same request. Is that what you have in mind ?

Yes, that would be the workaround, but I don't see a strong argument why
we should cut the CT, CG -> CG, CCM(CT) case. 

> 
> > So I would be fine if we say CG -> CG, CCM(CT(CG)). That is new to me
> > and I haven't look into the implementation effort yet.
> >
> > CG, CT -> CG, CCM(CT) is something I'd like to have, but I don't know if
> > we need to force it (@David: would it be much effort on your side, just
> > for completeness sake?)
> 
> How would we document that ? We can't say anymore that CG takes
> precedence over CT. This would require documenting precisely how the
> different values are computed from each other in all cases, and would
> limit options for IPA modules. I fear we may corner ourselves.

This overlaps with the other mails of the thread and is answered there.
I'm going to post a proposal for that.

Regards,
Stefan

> 
> > CCM, CT -> CG(CT), CCM also feels natural to me, but without any known
> > usecase. (Maybe in calibration, where you want to force a unit ccm
> > and check the correctness of the gains)
> 
> I'm fine with this, we can document that CCM, when specified, overrides
> any computed value.
> 
> > CT, CG, CCM -> CG, CCM  I think we can agree on that one. It is
> > overspecified, but the lower level controls should win.
> 
> Yes, this is fine.
> 
> > > > Does that help or just confuse further?
> > > 
> > > Let's see how the discussion progresses :-) Thank you for your input.
> > > 
> > > > > > > Do you have a nice sentence for that?
> > > > > >
> > > > > > /me checks... I have a set of French proverbs, but none of the seem very
> > > > > > appropriate. Sorry :-)
> > > > >
> > > > > What about "If ColourGains and ColourTemperature are specified at the
> > > > > same time, ColourGains takes precedence. The same applies to
> > > > > ColourCorrectionMatrix."?
> > > > >
> > > > > We can discuss the final wording after feedback from David.
> > > > >
> > > > > > > > > +
> > > > > > > > > +        The metadata will only report measured colour temperature values when
> > > > > > > > > +        available, even if set manually.
> > > > > > > >
> > > > > > > > I'm not sure to understand this.
> > > > > > >
> > > > > > > This is based on the comment from Kieran:
> > > > > > > https://patchwork.libcamera.org/patch/20771/#30590 He wanted to prepare
> > > > > > > for cases (RPi) where no temperature gets estimated. Only measurements
> > > > > > > are returned in metadata. Manually set temperature is not reflected in
> > > > > > > the metadata. This has the nice side effect, that you can set
> > > > > > > AwbEnable=false, and still get temperature estimations in the metadata.
> > > > > >
> > > > > > This means that whether or not the estimated colour temperature will be
> > > > > > returned in metadata will be platform-dependent. Can we avoid that ? It
> > > > > > makes writing portable applications much more difficult.
> > > > > >
> > > > > > My other concern is that metadata is supposed to report the setting
> > > > > > applied to a frame. The general rule is that, if a control can be set,
> > > > > > the value that has been set for a frame is reported in metadata. There
> > > > > > are exception for trigger-like controls. As this example clearly shows,
> > > > > > having multiple controls that ultimately set the same values is also
> > > > > > problematic from this point of view. Do we need to set a rule that
> > > > > > higher-level controls that get translated to lower-level controls are
> > > > > > never reported in metadata ?
> > > > > >
> > > > > > If we do that, then we'll have ColourTemperature as a control being
> > > > > > defined differently from ColourTemperature as metadata. I'm not sure I
> > > > > > like it much. Should we have two different controls ?
> > > > >
> > > > > We could split that to "MeasuredColourTemperature" and
> > > > > "AppliedColorTemperature". But there are always cases where one of them
> > > > > (or both) is not available (as discussed on Patch 3). I think on rkisp
> > > > > we could ensure that MeasuredColourTemperature is always available and
> > > > > contains "something" as the statistics are always available. But in the
> > > > > end as a user I'd prefer to know when the algorithm failed to deduce a
> > > > > valid colour temperature.
> > > 
> > > If the algorithm failed to estimate the colour temperature, that should
> > > be indicated by the absence of an estimated colour temperature in
> > > metadata.
> > > 
> > > David, why do you (if I understand correctly) stop estimating the colour
> > > temperature from the statistics in manual AWB mode ?
> > > 
> > > > > > > > > +
> > > > > > > > > +        \sa AwbEnable
> > > > > > > > > +        \sa ColourCorrectionMatrix
> > > > > > > > > +        \sa ColourGains
> > > > > > > > >
> > > > > > > > >    - Saturation:
> > > > > > > > >        type: float
> > > > > > > > > @@ -365,6 +379,8 @@ controls:
> > > > > > > > >          transformation. The 3x3 matrix is stored in conventional reading
> > > > > > > > >          order in an array of 9 floating point values.
> > > > > > > > >
> > > > > > > > > +        \sa AwbEnable
> > > > > > > > > +        \sa ColourTemperature
> > > > > > > > >        size: [3,3]
> > > > > > > > >
> > > > > > > > >    - ScalerCrop:
> 
> -- 
> Regards,
> 
> Laurent Pinchart

Hi Laurent,

maybe it's easiest to post the updated documentation diff before posting
the v6. I believe the rest is easy...

diff --git a/src/libcamera/control_ids_core.yaml b/src/libcamera/control_ids_core.yaml
index d45cf8e56187..2317515d6e8d 100644
--- a/src/libcamera/control_ids_core.yaml
+++ b/src/libcamera/control_ids_core.yaml
@@ -283,7 +283,19 @@ controls:
       description: |
         Enable or disable the AWB.

+        When AWB is enabled, the algorithm estimates the colour temperature of
+        the scene and computes colour gains and the colour correction matrix
+        automatically. The computed colour temperature, gains and correction
+        matrix are reported in metadata. The corresponding controls are ignored
+        if set in a request.
+
+        When AWB is disabled, the colour temperature, gains and correction
+        matrix are not updated automatically and can be set manually in
+        requests.
+
+        \sa ColourCorrectionMatrix
         \sa ColourGains
+        \sa ColourTemperature

   # AwbMode needs further attention:
   # - Auto-generate max enum value.
@@ -338,17 +350,34 @@ controls:
         Pair of gain values for the Red and Blue colour channels, in that
         order.

-        ColourGains can only be applied in a Request when the AWB is disabled.
+        ColourGains can only be applied in a Request when the AWB is disabled.
+        If ColourGains is set in a request but ColourTemperature is not, the
+        implementation shall calculate and set the ColourTemperature based on
+        the ColourGains.

         \sa AwbEnable
+        \sa ColourTemperature
       size: [2]

   - ColourTemperature:
       type: int32_t
       description: |
-        Report the estimate of the colour temperature for the frame, in kelvin.
+        ColourTemperature of the frame, in kelvin.
+
+        ColourTemperature can only be applied in a Request when the AWB is
+        disabled.
+
+        If ColourTemperature is set in a request but ColourGains is not, the
+        implementation shall calculate and set the ColourGains based on the
+        given ColourTemperature. If ColourTemperature is set but
+        ColourCorrectionMarix is not, the ColourCorrectionMarix is updated based
+        on the ColourTemperature.
+
+        The ColourTemperature used to process the frame is reported in metadata.

-        The ColourTemperature control can only be returned in metadata.
+        \sa AwbEnable
+        \sa ColourCorrectionMatrix
+        \sa ColourGains

   - Saturation:
       type: float
@@ -405,6 +434,11 @@ controls:
         stored in conventional reading order in an array of 9 floating point
         values.

+        ColourCorrectionMatrix can only be applied in a Request when the AWB is
+        disabled.
+
+        \sa AwbEnable
+        \sa ColourTemperature
       size: [3,3]

   - ScalerCrop:


Cheers,
Stefan

On Tue, Dec 10, 2024 at 04:34:11PM +0100, Stefan Klug wrote:
> Hi Laurent,
> 
> On Mon, Dec 09, 2024 at 03:02:09AM +0200, Laurent Pinchart wrote:
> > Looks like I forgot to reply to this.
> > 
> > On Mon, Sep 02, 2024 at 08:28:24AM +0100, Naushir Patuck wrote:
> > > On Sat, 31 Aug 2024 at 16:16, Laurent Pinchart wrote:
> > > > On Fri, Aug 30, 2024 at 04:31:50PM +0100, David Plowman wrote:
> > > > > On Fri, 30 Aug 2024 at 12:21, Stefan Klug wrote:
> > > > > > On Fri, Aug 30, 2024 at 01:15:55PM +0300, Laurent Pinchart wrote:
> > > > > > > On Fri, Aug 30, 2024 at 07:58:31AM +0200, Stefan Klug wrote:
> > > > > > > > On Fri, Aug 30, 2024 at 02:01:19AM +0300, Laurent Pinchart wrote:
> > > > > > > > > On Tue, Aug 13, 2024 at 10:44:18AM +0200, Stefan Klug wrote:
> > > > > > > > > > For manual control it is helpful to be able to specify a fixed colour
> > > > > > > > > > temperature. It also provides an easy way to apply the temperature
> > > > > > > > > > specific CCMs and colour gains that are contained in the tuning files.
> > > > > > > > > >
> > > > > > > > > > Document this and update the control dependencies.
> > > > > > > > > >
> > > > > > > > > > Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com>
> > > > > > > > > > ---
> > > > > > > > > >  src/libcamera/control_ids_core.yaml | 24 ++++++++++++++++++++----
> > > > > > > > > >  1 file changed, 20 insertions(+), 4 deletions(-)
> > > > > > > > > >
> > > > > > > > > > diff --git a/src/libcamera/control_ids_core.yaml b/src/libcamera/control_ids_core.yaml
> > > > > > > > > > index cf40771d3896..04dcc4af67fc 100644
> > > > > > > > > > --- a/src/libcamera/control_ids_core.yaml
> > > > > > > > > > +++ b/src/libcamera/control_ids_core.yaml
> > > > > > > > > > @@ -252,9 +252,12 @@ controls:
> > > > > > > > > >    - AwbEnable:
> > > > > > > > > >        type: bool
> > > > > > > > > >        description: |
> > > > > > > > > > -        Enable or disable the AWB.
> > > > > > > > > > +        Enable or disable the AWB. Disabling AWB stops updates to the
> > > > > > > > > > +        ColourGains and to the ColourCorrectionMatrix.
> > > > > > > > >
> > > > > > > > > Please split this in two paragraphs. The first paragraph is translated
> > > > > > > > > to a \brief doxygen command, and should be a single sentence. Same
> > > > > > > > > below.
> > > > > > > > >
> > > > > > > > > I would like to clarify this a bit. Here's an attempt, is it what you
> > > > > > > > > mean ?
> > > > > > > > >
> > > > > > > > >   Enable or disable the AWB.
> > > > > > > > >
> > > > > > > > >   When AWB is enabled, the algorithm estimates the colour temperature of
> > > > > > > > >   the scene, and computes colour gains and the colour correction matrix
> > > > > > > > >   automatically. The computed colour temperate, gains and correction
> > > > > > > > >   matrix are reported in metadata. The corresponding controls are ignored
> > > > > > > > >   if set in a request.
> > > > > > > > >
> > > > > > > > >   When AWB is disabled, the colour temperature, gains and correction
> > > > > > > > >   matrix are not updated automatically and can be set manually in
> > > > > > > > >   requests.
> > > > > > > >
> > > > > > > > Looks good, I'll apply that.
> > > > > > > >
> > > > > > > > > >
> > > > > > > > > > +        \sa ColourCorrectionMatrix
> > > > > > > > > >          \sa ColourGains
> > > > > > > > > > +        \sa ColourTemperature
> > > > > > > > > >
> > > > > > > > > >    # AwbMode needs further attention:
> > > > > > > > > >    # - Auto-generate max enum value.
> > > > > > > > > > @@ -309,13 +312,24 @@ controls:
> > > > > > > > > >          disabled.
> > > > > > > > > >
> > > > > > > > > >          \sa AwbEnable
> > > > > > > > > > +        \sa ColourTemperature
> > > > > > > > > >        size: [2]
> > > > > > > > > >
> > > > > > > > > >    - ColourTemperature:
> > > > > > > > > >        type: int32_t
> > > > > > > > > > -      description: Report the current estimate of the colour temperature, in
> > > > > > > > > > -        kelvin, for this frame. The ColourTemperature control can only be
> > > > > > > > > > -        returned in metadata.
> > > > > > > > > > +      description: |
> > > > > > > > > > +        Report the current estimate of the colour temperature, in kelvin, for
> > > > > > > > > > +        this frame. An implementation may also allow this control to be set when
> > > > > > > > >
> > > > > > > > > s/also //
> > > > > > > > >
> > > > > > > > > > +        AWB is disabled. In that case ColourGains and the ColourCorrectionMatrix
> > > > > > > > > > +        get set accordingly. If either ColourGains or ColourCorrectionMatrix are
> > > > > > > > > > +        specified at the same time, they take precedence.
> > > > > > > > >
> > > > > > > > > maybe "they take precedence, and the ColourTemperature is ignored" ? Or,
> > > > > > > > > if an application sets ColourTemperature and ColourGains but not
> > > > > > > > > ColourCorrectionMatrix, do you expect the implementation to apply the
> > > > > > > > > requested ColourGains and set ColourCorrectionMatrix based on the
> > > > > > > > > temperature ?
> > > > > > > >
> > > > > > > > The latter is exactly what happens. The following table lists the
> > > > > > > > possible options:
> > > > > > > >
> > > > > > > > CT -> CG(CT), CCM(CT)
> > > > > > > > CT, CG -> CG, CCM(CT)
> > > > > > > > CT, CCM -> CG(CT), CCM
> > > > > > > > CT, CG, CCM -> CG, CCM
> > > > > > >
> > > > > > > David, is this the behaviour you would also expect for Raspberry Pi ?
> > > > >
> > > > > I'm guessing the question here is really what to do if an application
> > > > > sets both CT and CG together? The other cases seem fairly
> > > > > uncontroversial (?).
> > > >
> > > > As far as I understand, for the rkisp1, the colour gains and the CCM are
> > > > both calculated based on the colour temperature. The case where the
> > > > application sets CT and CG is conceptually as problematic as the case
> > > > where it sets CT and CCM. Stefan, is that correct ?
> > > >
> > > > > For us, I'm not sure it really makes much sense to supply both CT and
> > > > > CG at once. When someone sets CG, the algorithm estimates the CT and
> > > > > passes this to other algorithms, like lens shading and CCM. (So we
> > > > > actually have a "CG -> CG, CT(CG), CCM(CT)" kind of case going on.)
> > > >
> > > > When an application sets CG, does the algorithm estimate CT from the
> > > > stats, or from the CG alone for RPi ? Stefan, how about your plans for
> > > > rkisp1 ?
> > > 
> > > When an application sets manual CGs, the algorithm estimates the CT
> > > from the CT-curve in the tuning directly.
> > 
> > I'll try to recap what we have (hopefully) agreed on so far.
> > 
> > OK, so in manual AWB mode, CT and CG are interchangeable, one will be
> > calculated from the other based on the tuning data, without taking
> > statistics into account. As this is a pure software implementation, if
> > both controls are specified, we can freely specify which one takes
> > precedence, and this can be applied to all platforms. I have a
> > preference for making the gains take precedence (as Stefan did in v5) as
> > they provide more precise control.
> 
> As written in the next paragraph, I propose for no precedence between CG
> and CT at all as we would unnecessarily limit our options.
> 
> > 
> > In auto AWB mode, CG and CT are both calculated by the AWB algorithm and
> > any value set through controls is ignored.
> > 
> > So far, so good ?
> > 
> > The next question is how to handle CCM. Auto mode is easy, CCM is
> > computed automatically, and any value set through controls is ignored.
> > In manual mode, if CCM is set in a request, its value should be applied.
> > What if a request contains CG or CT and no CCM ? Would CCM be computed
> > by the AWB algorithm (in manual mode), or its previous value retained ?
> > 
> 
> I prepared a new update to the controls documentation, that I'll post
> shortly. The proposal there is (for manual mode only):
> 
> - CG updates CT if CT is not set.
> - CT updates CG if CG is not set.
> - CT updates CCM if CCM is not set (Which could be triggered by the CG ->
>   CT -> CCM chain)
> 
> That seems to be easiest to explain at the moment captures most use
> cases.
> 
> > > > > When I add this new control, it will calculate CG from the calibrated
> > > > > colour temperature curve in the camera tuning and use those, and pass
> > > > > the CT to those other algorithms (so like the first row in the table).
> > > >
> > > > That's the main use, and I think we all agree on the behaviour. It seems
> > > > quite uncontroversial.
> > > >
> > > > > I don't think I particularly want to implement cases where it takes a
> > > > > CG value, uses them, and also a random CT which it then passes on?
> > > > > Possibly I'd rather leave these cases (where we have both CT and CG on
> > > > > the LHS) as either "implementation dependent" or just "undefined", and
> > > > > recommend setting one or other.
> > > >
> > > > I dislike implementation-dependent behaviours if we can avoid them, at
> > > > least in cases that we consider valid use cases. Is there a valid use
> > > > case for setting CT along with CG or CCM ? It sounds to me like there
> > > > wouldn't be one for RPi. Stefan, how about you ?
> > > 
> > > I don't think RPi has a use case that requires the CT and CGs to be both set.
> > > 
> > > > > Does that help or just confuse further?
> > > >
> > > > Let's see how the discussion progresses :-) Thank you for your input.
> > > >
> > > > > > > > Do you have a nice sentence for that?
> > > > > > >
> > > > > > > /me checks... I have a set of French proverbs, but none of the seem very
> > > > > > > appropriate. Sorry :-)
> > > > > >
> > > > > > What about "If ColourGains and ColourTemperature are specified at the
> > > > > > same time, ColourGains takes precedence. The same applies to
> > > > > > ColourCorrectionMatrix."?
> > > > > >
> > > > > > We can discuss the final wording after feedback from David.
> > > > > >
> > > > > > > > > > +
> > > > > > > > > > +        The metadata will only report measured colour temperature values when
> > > > > > > > > > +        available, even if set manually.
> > > > > > > > >
> > > > > > > > > I'm not sure to understand this.
> > > > > > > >
> > > > > > > > This is based on the comment from Kieran:
> > > > > > > > https://patchwork.libcamera.org/patch/20771/#30590 He wanted to prepare
> > > > > > > > for cases (RPi) where no temperature gets estimated. Only measurements
> > > > > > > > are returned in metadata. Manually set temperature is not reflected in
> > > > > > > > the metadata. This has the nice side effect, that you can set
> > > > > > > > AwbEnable=false, and still get temperature estimations in the metadata.
> > > > > > >
> > > > > > > This means that whether or not the estimated colour temperature will be
> > > > > > > returned in metadata will be platform-dependent. Can we avoid that ? It
> > > > > > > makes writing portable applications much more difficult.
> > > > > > >
> > > > > > > My other concern is that metadata is supposed to report the setting
> > > > > > > applied to a frame. The general rule is that, if a control can be set,
> > > > > > > the value that has been set for a frame is reported in metadata. There
> > > > > > > are exception for trigger-like controls. As this example clearly shows,
> > > > > > > having multiple controls that ultimately set the same values is also
> > > > > > > problematic from this point of view. Do we need to set a rule that
> > > > > > > higher-level controls that get translated to lower-level controls are
> > > > > > > never reported in metadata ?
> > > > > > >
> > > > > > > If we do that, then we'll have ColourTemperature as a control being
> > > > > > > defined differently from ColourTemperature as metadata. I'm not sure I
> > > > > > > like it much. Should we have two different controls ?
> > > > > >
> > > > > > We could split that to "MeasuredColourTemperature" and
> > > > > > "AppliedColorTemperature". But there are always cases where one of them
> > > > > > (or both) is not available (as discussed on Patch 3). I think on rkisp
> > > > > > we could ensure that MeasuredColourTemperature is always available and
> > > > > > contains "something" as the statistics are always available. But in the
> > > > > > end as a user I'd prefer to know when the algorithm failed to deduce a
> > > > > > valid colour temperature.
> > > >
> > > > If the algorithm failed to estimate the colour temperature, that should
> > > > be indicated by the absence of an estimated colour temperature in
> > > > metadata.
> > > >
> > > > David, why do you (if I understand correctly) stop estimating the colour
> > > > temperature from the statistics in manual AWB mode ?
> > > 
> > > I think it's to keep things consistent.  The CT-curve in the tuning
> > > file is taken as the canonical truth. So if manual CGs are applied,
> > > and assuming the users know what they are doing(!), we return a simple
> > > lookup without going through all the computations again.  Of course,
> > > this is simple enough to change in our code if the need arises.
> > 
> > I'm fine with that behaviour, but I would like to keep the metadata
> > behaviour consistent between platforms.
> > 
> > For auto-mode, I think we all agree that the CG, CT and CCM metadata
> > will report the values computed by the AWB algorithm (please wave if
> > you disagree).
> > 
> > For manual mode, we've discussed two different behaviours that apply to
> > CG, CT and CCM:
> > 
> > - Report the controls that are applied to the device. This matches the
> >   standard libcamera metadata behaviour.
> > 
> > - Let the AWB algorithm continue to process statistics, and report the
> >   estimated values. As far as I understand, this was requested for CT
> >   estimation only, not for CG or CCM estimation.
> > 
> > While I understand that continuous CT estimation in manual mode can be
> > tempting, I think it would require more discussions to specify it
> > unambiguously. Stefan, Kieran, do you have a use case for this now, or
> > is this something you considered as a nice-to-have feature ?
> 
> The discussion roughly went as follows:
> 
> There are valid cases for both colour temperatures. The one from the
> statistics engine (measuredTemp) would be very useful to do any manual
> regulation (outside of libcamera). The one used in the ISP for
> processing the frame at hand (usedTemp) is useful to store in image
> metadata or similar things. But for none of them there is a hard use
> case.
> 
> The issue with usedTemp is that it is not well defined in manual mode.
> At the time this was discussed we also had no way on rkisp1 to map from
> CG to CT. As you lean towards that value I propose the following:
> 
> CT: usedTemp = CT, correct
> CG: usedTemp = CT(CG), correct (now possible on rkisp1 also)
> CT,CG: usedTemp = CT, incorrect because CG not taken into account but best
> effort
> CCM: usedTemp is unchanged, incorrect but best effort
> 
> I think we can live with that incorrectness as it only affects corner
> cases.
> 
> For the measuredTemp we can easily introduce a MeasuredColourTemperature
> metadata at a later stage.
> 
> Regards,
> Stefan
> 
> > 
> > > > > > > > > > +
> > > > > > > > > > +        \sa AwbEnable
> > > > > > > > > > +        \sa ColourCorrectionMatrix
> > > > > > > > > > +        \sa ColourGains
> > > > > > > > > >
> > > > > > > > > >    - Saturation:
> > > > > > > > > >        type: float
> > > > > > > > > > @@ -365,6 +379,8 @@ controls:
> > > > > > > > > >          transformation. The 3x3 matrix is stored in conventional reading
> > > > > > > > > >          order in an array of 9 floating point values.
> > > > > > > > > >
> > > > > > > > > > +        \sa AwbEnable
> > > > > > > > > > +        \sa ColourTemperature
> > > > > > > > > >        size: [3,3]
> > > > > > > > > >
> > > > > > > > > >    - ScalerCrop:
> > 
> > -- 
> > Regards,
> > 
> > Laurent Pinchart

Hi Stefan,

On Tue, Dec 10, 2024 at 05:00:29PM +0100, Stefan Klug wrote:
> On Mon, Dec 09, 2024 at 03:47:29AM +0200, Laurent Pinchart wrote:
> > On Mon, Sep 02, 2024 at 10:32:59AM +0200, Stefan Klug wrote:
> > > On Sat, Aug 31, 2024 at 06:16:10PM +0300, Laurent Pinchart wrote:
> > > > On Fri, Aug 30, 2024 at 04:31:50PM +0100, David Plowman wrote:
> > > > > On Fri, 30 Aug 2024 at 12:21, Stefan Klug wrote:
> > > > > > On Fri, Aug 30, 2024 at 01:15:55PM +0300, Laurent Pinchart wrote:
> > > > > > > On Fri, Aug 30, 2024 at 07:58:31AM +0200, Stefan Klug wrote:
> > > > > > > > On Fri, Aug 30, 2024 at 02:01:19AM +0300, Laurent Pinchart wrote:
> > > > > > > > > On Tue, Aug 13, 2024 at 10:44:18AM +0200, Stefan Klug wrote:
> > > > > > > > > > For manual control it is helpful to be able to specify a fixed colour
> > > > > > > > > > temperature. It also provides an easy way to apply the temperature
> > > > > > > > > > specific CCMs and colour gains that are contained in the tuning files.
> > > > > > > > > >
> > > > > > > > > > Document this and update the control dependencies.
> > > > > > > > > >
> > > > > > > > > > Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com>
> > > > > > > > > > ---
> > > > > > > > > >  src/libcamera/control_ids_core.yaml | 24 ++++++++++++++++++++----
> > > > > > > > > >  1 file changed, 20 insertions(+), 4 deletions(-)
> > > > > > > > > >
> > > > > > > > > > diff --git a/src/libcamera/control_ids_core.yaml b/src/libcamera/control_ids_core.yaml
> > > > > > > > > > index cf40771d3896..04dcc4af67fc 100644
> > > > > > > > > > --- a/src/libcamera/control_ids_core.yaml
> > > > > > > > > > +++ b/src/libcamera/control_ids_core.yaml
> > > > > > > > > > @@ -252,9 +252,12 @@ controls:
> > > > > > > > > >    - AwbEnable:
> > > > > > > > > >        type: bool
> > > > > > > > > >        description: |
> > > > > > > > > > -        Enable or disable the AWB.
> > > > > > > > > > +        Enable or disable the AWB. Disabling AWB stops updates to the
> > > > > > > > > > +        ColourGains and to the ColourCorrectionMatrix.
> > > > > > > > >
> > > > > > > > > Please split this in two paragraphs. The first paragraph is translated
> > > > > > > > > to a \brief doxygen command, and should be a single sentence. Same
> > > > > > > > > below.
> > > > > > > > >
> > > > > > > > > I would like to clarify this a bit. Here's an attempt, is it what you
> > > > > > > > > mean ?
> > > > > > > > >
> > > > > > > > >   Enable or disable the AWB.
> > > > > > > > >
> > > > > > > > >   When AWB is enabled, the algorithm estimates the colour temperature of
> > > > > > > > >   the scene, and computes colour gains and the colour correction matrix
> > > > > > > > >   automatically. The computed colour temperate, gains and correction
> > > > > > > > >   matrix are reported in metadata. The corresponding controls are ignored
> > > > > > > > >   if set in a request.
> > > > > > > > >
> > > > > > > > >   When AWB is disabled, the colour temperature, gains and correction
> > > > > > > > >   matrix are not updated automatically and can be set manually in
> > > > > > > > >   requests.
> > > > > > > >
> > > > > > > > Looks good, I'll apply that.
> > > > > > > >
> > > > > > > > > >
> > > > > > > > > > +        \sa ColourCorrectionMatrix
> > > > > > > > > >          \sa ColourGains
> > > > > > > > > > +        \sa ColourTemperature
> > > > > > > > > >
> > > > > > > > > >    # AwbMode needs further attention:
> > > > > > > > > >    # - Auto-generate max enum value.
> > > > > > > > > > @@ -309,13 +312,24 @@ controls:
> > > > > > > > > >          disabled.
> > > > > > > > > >
> > > > > > > > > >          \sa AwbEnable
> > > > > > > > > > +        \sa ColourTemperature
> > > > > > > > > >        size: [2]
> > > > > > > > > >
> > > > > > > > > >    - ColourTemperature:
> > > > > > > > > >        type: int32_t
> > > > > > > > > > -      description: Report the current estimate of the colour temperature, in
> > > > > > > > > > -        kelvin, for this frame. The ColourTemperature control can only be
> > > > > > > > > > -        returned in metadata.
> > > > > > > > > > +      description: |
> > > > > > > > > > +        Report the current estimate of the colour temperature, in kelvin, for
> > > > > > > > > > +        this frame. An implementation may also allow this control to be set when
> > > > > > > > >
> > > > > > > > > s/also //
> > > > > > > > >
> > > > > > > > > > +        AWB is disabled. In that case ColourGains and the ColourCorrectionMatrix
> > > > > > > > > > +        get set accordingly. If either ColourGains or ColourCorrectionMatrix are
> > > > > > > > > > +        specified at the same time, they take precedence.
> > > > > > > > >
> > > > > > > > > maybe "they take precedence, and the ColourTemperature is ignored" ? Or,
> > > > > > > > > if an application sets ColourTemperature and ColourGains but not
> > > > > > > > > ColourCorrectionMatrix, do you expect the implementation to apply the
> > > > > > > > > requested ColourGains and set ColourCorrectionMatrix based on the
> > > > > > > > > temperature ?
> > > > > > > >
> > > > > > > > The latter is exactly what happens. The following table lists the
> > > > > > > > possible options:
> > > > > > > >
> > > > > > > > CT -> CG(CT), CCM(CT)
> > > > > > > > CT, CG -> CG, CCM(CT)
> > > > > > > > CT, CCM -> CG(CT), CCM
> > > > > > > > CT, CG, CCM -> CG, CCM
> > > > > > >
> > > > > > > David, is this the behaviour you would also expect for Raspberry Pi ?
> > > > > 
> > > > > I'm guessing the question here is really what to do if an application
> > > > > sets both CT and CG together? The other cases seem fairly
> > > > > uncontroversial (?).
> > > > 
> > > > As far as I understand, for the rkisp1, the colour gains and the CCM are
> > > > both calculated based on the colour temperature. The case where the
> > > > application sets CT and CG is conceptually as problematic as the case
> > > > where it sets CT and CCM. Stefan, is that correct ?
> > > 
> > > Only CCM is set based on CT. CG is set based on the stats and these are
> > > also used to calculate the CT. As David noted CG -> CT(CG) -> CCM(CT) is
> > > possible. CT(CCM) is not possible afaik. So the cases are similar but
> > > not the same.
> > > 
> > > > > For us, I'm not sure it really makes much sense to supply both CT and
> > > > > CG at once. When someone sets CG, the algorithm estimates the CT and
> > > > > passes this to other algorithms, like lens shading and CCM. (So we
> > > > > actually have a "CG -> CG, CT(CG), CCM(CT)" kind of case going on.)
> > > > 
> > > > When an application sets CG, does the algorithm estimate CT from the
> > > > stats, or from the CG alone for RPi ? Stefan, how about your plans for
> > > > rkisp1 ?
> > > 
> > > At the moment, we do not estimate CT from CG. But that might be worth to
> > > do.
> > > 
> > > > > When I add this new control, it will calculate CG from the calibrated
> > > > > colour temperature curve in the camera tuning and use those, and pass
> > > > > the CT to those other algorithms (so like the first row in the table).
> > > > 
> > > > That's the main use, and I think we all agree on the behaviour. It seems
> > > > quite uncontroversial.
> > > 
> > > Yes, I think on that one we are all fine.
> > > So CT -> CG(CT), CCM(CT) is accepted. Metadata might be an open point
> > > here.
> > > 
> > > > > I don't think I particularly want to implement cases where it takes a
> > > > > CG value, uses them, and also a random CT which it then passes on?
> > > > > Possibly I'd rather leave these cases (where we have both CT and CG on
> > > > > the LHS) as either "implementation dependent" or just "undefined", and
> > > > > recommend setting one or other.
> > > > 
> > > > I dislike implementation-dependent behaviours if we can avoid them, at
> > > > least in cases that we consider valid use cases. Is there a valid use
> > > > case for setting CT along with CG or CCM ? It sounds to me like there
> > > > wouldn't be one for RPi. Stefan, how about you ?
> > > 
> > > To me the most prominent use case is manual WB. So the user takes a
> > > picture of a gray patch and the application (not libcamera) calculates
> > > wb gains based on that. If you compare to a typical digital camera I
> > > think one would expect the following to happen: CG -> CT(CG) -> CCM(CT)
> > > 
> > > In rkisp1 we don't have that CG->CT(CG) step, but that doesn't mean we
> > > shouldn't do it.
> > 
> > To make sure I understand you correctly, what you're proposing is
> > 
> > - AWB disabled
> > - Application sets CG
> > - IPA computes CT(CG) and CCM(CG,CT), and applies CCM
> > 
> > Note that I wrote CCM(CG,CT) to let implementations decide how to
> > compute CCM. Whether they use CG, CT or both is an implementation
> > detail. Statistics are *not* used to compute either CT or CCM, they are
> > completely ignored.
> > 
> > Is that right ? That seems easy to specify and implement, so I'm fine
> > with it. The use case with CG and CT swapped would be
> > 
> > - AWB disabled
> > - Application sets CT
> > - IPA computes CG(CT) and CCM(CG,CT), and applies CCM
> > 
> > can easily be supported too, and the two options don't conflict with
> > each other as they're user-selectable (by setting either CG or CT).
> > 
> > > Looking at that with the eyes of a machine-vision user it would be
> > > counter intuitive that the CCM suddenly changes when I change the CG.
> > 
> > Could you elaborate on why that is the case ?
> 
> I guess it stems from the model of MV cameras. In SFNC there is no
> notion of colour temperature at all, but colour gains and ccm. ccm for
> colour space transform and cg for the white balance. Both can be
> described using calibration and a colour temperature but are otherwise
> completely independent. As these cameras tend to have no ct estimation
> at all and only do grey world model white balance, this is also not
> needed. So I'm used to loading a ccm for a given light source (in our
> case by specifying a CT) and then adjust the cg to reproduce grays as
> grays. But that is quit theoretical. 
> (See also https://docs.baslerweb.com/light-source-preset )

I see where that comes from, but it sounds like you'd like to have two
mutually exclusive behaviours:

- A greyworld, machine vision behaviour where there's not CT, and where
  CG and CCM are set manually and separately.

- An automatic model where CCM is computed by AWB based on CT, and where
  you want AWB to estimate CT from CG.

Asking for AWB to estimate CT from CG and set CCM accordingly, while at
the same asking for CCM not to be overridden, seems contradicting.

> > > But that can be worked around from user side, by supplying a manual CCM
> > > in the request. Which brings me to the next point. The CCM is the only
> > > parameter here, that is basically impossible to handcraft in an
> > > application. So there might be use cases where I'd like to set a CCM
> > > based on a color temperature and then hand tweak the CG.
> > 
> > To do so, you would need to set the CG, wait until it gets applied,
> > retrieved the CCM from the metadata, and then change the CG while
> > specifying the CCM in the same request. Is that what you have in mind ?
> 
> Yes, that would be the workaround, but I don't see a strong argument why
> we should cut the CT, CG -> CG, CCM(CT) case. 

I suppose we could. It's going to be fun to document, but we can give it
a try.

> > > So I would be fine if we say CG -> CG, CCM(CT(CG)). That is new to me
> > > and I haven't look into the implementation effort yet.
> > >
> > > CG, CT -> CG, CCM(CT) is something I'd like to have, but I don't know if
> > > we need to force it (@David: would it be much effort on your side, just
> > > for completeness sake?)
> > 
> > How would we document that ? We can't say anymore that CG takes
> > precedence over CT. This would require documenting precisely how the
> > different values are computed from each other in all cases, and would
> > limit options for IPA modules. I fear we may corner ourselves.
> 
> This overlaps with the other mails of the thread and is answered there.
> I'm going to post a proposal for that.
> 
> > > CCM, CT -> CG(CT), CCM also feels natural to me, but without any known
> > > usecase. (Maybe in calibration, where you want to force a unit ccm
> > > and check the correctness of the gains)
> > 
> > I'm fine with this, we can document that CCM, when specified, overrides
> > any computed value.
> > 
> > > CT, CG, CCM -> CG, CCM  I think we can agree on that one. It is
> > > overspecified, but the lower level controls should win.
> > 
> > Yes, this is fine.
> > 
> > > > > Does that help or just confuse further?
> > > > 
> > > > Let's see how the discussion progresses :-) Thank you for your input.
> > > > 
> > > > > > > > Do you have a nice sentence for that?
> > > > > > >
> > > > > > > /me checks... I have a set of French proverbs, but none of the seem very
> > > > > > > appropriate. Sorry :-)
> > > > > >
> > > > > > What about "If ColourGains and ColourTemperature are specified at the
> > > > > > same time, ColourGains takes precedence. The same applies to
> > > > > > ColourCorrectionMatrix."?
> > > > > >
> > > > > > We can discuss the final wording after feedback from David.
> > > > > >
> > > > > > > > > > +
> > > > > > > > > > +        The metadata will only report measured colour temperature values when
> > > > > > > > > > +        available, even if set manually.
> > > > > > > > >
> > > > > > > > > I'm not sure to understand this.
> > > > > > > >
> > > > > > > > This is based on the comment from Kieran:
> > > > > > > > https://patchwork.libcamera.org/patch/20771/#30590 He wanted to prepare
> > > > > > > > for cases (RPi) where no temperature gets estimated. Only measurements
> > > > > > > > are returned in metadata. Manually set temperature is not reflected in
> > > > > > > > the metadata. This has the nice side effect, that you can set
> > > > > > > > AwbEnable=false, and still get temperature estimations in the metadata.
> > > > > > >
> > > > > > > This means that whether or not the estimated colour temperature will be
> > > > > > > returned in metadata will be platform-dependent. Can we avoid that ? It
> > > > > > > makes writing portable applications much more difficult.
> > > > > > >
> > > > > > > My other concern is that metadata is supposed to report the setting
> > > > > > > applied to a frame. The general rule is that, if a control can be set,
> > > > > > > the value that has been set for a frame is reported in metadata. There
> > > > > > > are exception for trigger-like controls. As this example clearly shows,
> > > > > > > having multiple controls that ultimately set the same values is also
> > > > > > > problematic from this point of view. Do we need to set a rule that
> > > > > > > higher-level controls that get translated to lower-level controls are
> > > > > > > never reported in metadata ?
> > > > > > >
> > > > > > > If we do that, then we'll have ColourTemperature as a control being
> > > > > > > defined differently from ColourTemperature as metadata. I'm not sure I
> > > > > > > like it much. Should we have two different controls ?
> > > > > >
> > > > > > We could split that to "MeasuredColourTemperature" and
> > > > > > "AppliedColorTemperature". But there are always cases where one of them
> > > > > > (or both) is not available (as discussed on Patch 3). I think on rkisp
> > > > > > we could ensure that MeasuredColourTemperature is always available and
> > > > > > contains "something" as the statistics are always available. But in the
> > > > > > end as a user I'd prefer to know when the algorithm failed to deduce a
> > > > > > valid colour temperature.
> > > > 
> > > > If the algorithm failed to estimate the colour temperature, that should
> > > > be indicated by the absence of an estimated colour temperature in
> > > > metadata.
> > > > 
> > > > David, why do you (if I understand correctly) stop estimating the colour
> > > > temperature from the statistics in manual AWB mode ?
> > > > 
> > > > > > > > > > +
> > > > > > > > > > +        \sa AwbEnable
> > > > > > > > > > +        \sa ColourCorrectionMatrix
> > > > > > > > > > +        \sa ColourGains
> > > > > > > > > >
> > > > > > > > > >    - Saturation:
> > > > > > > > > >        type: float
> > > > > > > > > > @@ -365,6 +379,8 @@ controls:
> > > > > > > > > >          transformation. The 3x3 matrix is stored in conventional reading
> > > > > > > > > >          order in an array of 9 floating point values.
> > > > > > > > > >
> > > > > > > > > > +        \sa AwbEnable
> > > > > > > > > > +        \sa ColourTemperature
> > > > > > > > > >        size: [3,3]
> > > > > > > > > >
> > > > > > > > > >    - ScalerCrop:

On Tue, Dec 10, 2024 at 05:14:30PM +0100, Stefan Klug wrote:
> Hi Laurent,
> 
> maybe it's easiest to post the updated documentation diff before posting
> the v6. I believe the rest is easy...
> 
> diff --git a/src/libcamera/control_ids_core.yaml b/src/libcamera/control_ids_core.yaml
> index d45cf8e56187..2317515d6e8d 100644
> --- a/src/libcamera/control_ids_core.yaml
> +++ b/src/libcamera/control_ids_core.yaml
> @@ -283,7 +283,19 @@ controls:
>        description: |
>          Enable or disable the AWB.
> 
> +        When AWB is enabled, the algorithm estimates the colour temperature of
> +        the scene and computes colour gains and the colour correction matrix
> +        automatically. The computed colour temperature, gains and correction
> +        matrix are reported in metadata. The corresponding controls are ignored
> +        if set in a request.
> +
> +        When AWB is disabled, the colour temperature, gains and correction
> +        matrix are not updated automatically and can be set manually in
> +        requests.
> +
> +        \sa ColourCorrectionMatrix
>          \sa ColourGains
> +        \sa ColourTemperature
> 
>    # AwbMode needs further attention:
>    # - Auto-generate max enum value.
> @@ -338,17 +350,34 @@ controls:
>          Pair of gain values for the Red and Blue colour channels, in that
>          order.
> 
> -        ColourGains can only be applied in a Request when the AWB is disabled.
> +        ColourGains can only be applied in a Request when the AWB is disabled.
> +        If ColourGains is set in a request but ColourTemperature is not, the
> +        implementation shall calculate and set the ColourTemperature based on
> +        the ColourGains.
> 
>          \sa AwbEnable
> +        \sa ColourTemperature
>        size: [2]
> 
>    - ColourTemperature:
>        type: int32_t
>        description: |
> -        Report the estimate of the colour temperature for the frame, in kelvin.
> +        ColourTemperature of the frame, in kelvin.
> +
> +        ColourTemperature can only be applied in a Request when the AWB is
> +        disabled.
> +
> +        If ColourTemperature is set in a request but ColourGains is not, the
> +        implementation shall calculate and set the ColourGains based on the
> +        given ColourTemperature. If ColourTemperature is set but
> +        ColourCorrectionMarix is not, the ColourCorrectionMarix is updated based
> +        on the ColourTemperature.

        If ColourTemperature is set (either directly, or indirectly by setting
	ColourGains) but ColourCorrectionMatrix is not, the
	ColourCorrectionMatrix is updated based on the ColourTemperature.

> +
> +        The ColourTemperature used to process the frame is reported in metadata.
> 
> -        The ColourTemperature control can only be returned in metadata.
> +        \sa AwbEnable
> +        \sa ColourCorrectionMatrix
> +        \sa ColourGains
> 
>    - Saturation:
>        type: float
> @@ -405,6 +434,11 @@ controls:
>          stored in conventional reading order in an array of 9 floating point
>          values.
> 
> +        ColourCorrectionMatrix can only be applied in a Request when the AWB is
> +        disabled.
> +
> +        \sa AwbEnable
> +        \sa ColourTemperature

We can give this a try.

>        size: [3,3]
> 
>    - ScalerCrop:
> 
> On Tue, Dec 10, 2024 at 04:34:11PM +0100, Stefan Klug wrote:
> > On Mon, Dec 09, 2024 at 03:02:09AM +0200, Laurent Pinchart wrote:
> > > On Mon, Sep 02, 2024 at 08:28:24AM +0100, Naushir Patuck wrote:
> > > > On Sat, 31 Aug 2024 at 16:16, Laurent Pinchart wrote:
> > > > > On Fri, Aug 30, 2024 at 04:31:50PM +0100, David Plowman wrote:
> > > > > > On Fri, 30 Aug 2024 at 12:21, Stefan Klug wrote:
> > > > > > > On Fri, Aug 30, 2024 at 01:15:55PM +0300, Laurent Pinchart wrote:
> > > > > > > > On Fri, Aug 30, 2024 at 07:58:31AM +0200, Stefan Klug wrote:
> > > > > > > > > On Fri, Aug 30, 2024 at 02:01:19AM +0300, Laurent Pinchart wrote:
> > > > > > > > > > On Tue, Aug 13, 2024 at 10:44:18AM +0200, Stefan Klug wrote:
> > > > > > > > > > > For manual control it is helpful to be able to specify a fixed colour
> > > > > > > > > > > temperature. It also provides an easy way to apply the temperature
> > > > > > > > > > > specific CCMs and colour gains that are contained in the tuning files.
> > > > > > > > > > >
> > > > > > > > > > > Document this and update the control dependencies.
> > > > > > > > > > >
> > > > > > > > > > > Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com>
> > > > > > > > > > > ---
> > > > > > > > > > >  src/libcamera/control_ids_core.yaml | 24 ++++++++++++++++++++----
> > > > > > > > > > >  1 file changed, 20 insertions(+), 4 deletions(-)
> > > > > > > > > > >
> > > > > > > > > > > diff --git a/src/libcamera/control_ids_core.yaml b/src/libcamera/control_ids_core.yaml
> > > > > > > > > > > index cf40771d3896..04dcc4af67fc 100644
> > > > > > > > > > > --- a/src/libcamera/control_ids_core.yaml
> > > > > > > > > > > +++ b/src/libcamera/control_ids_core.yaml
> > > > > > > > > > > @@ -252,9 +252,12 @@ controls:
> > > > > > > > > > >    - AwbEnable:
> > > > > > > > > > >        type: bool
> > > > > > > > > > >        description: |
> > > > > > > > > > > -        Enable or disable the AWB.
> > > > > > > > > > > +        Enable or disable the AWB. Disabling AWB stops updates to the
> > > > > > > > > > > +        ColourGains and to the ColourCorrectionMatrix.
> > > > > > > > > >
> > > > > > > > > > Please split this in two paragraphs. The first paragraph is translated
> > > > > > > > > > to a \brief doxygen command, and should be a single sentence. Same
> > > > > > > > > > below.
> > > > > > > > > >
> > > > > > > > > > I would like to clarify this a bit. Here's an attempt, is it what you
> > > > > > > > > > mean ?
> > > > > > > > > >
> > > > > > > > > >   Enable or disable the AWB.
> > > > > > > > > >
> > > > > > > > > >   When AWB is enabled, the algorithm estimates the colour temperature of
> > > > > > > > > >   the scene, and computes colour gains and the colour correction matrix
> > > > > > > > > >   automatically. The computed colour temperate, gains and correction
> > > > > > > > > >   matrix are reported in metadata. The corresponding controls are ignored
> > > > > > > > > >   if set in a request.
> > > > > > > > > >
> > > > > > > > > >   When AWB is disabled, the colour temperature, gains and correction
> > > > > > > > > >   matrix are not updated automatically and can be set manually in
> > > > > > > > > >   requests.
> > > > > > > > >
> > > > > > > > > Looks good, I'll apply that.
> > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > > +        \sa ColourCorrectionMatrix
> > > > > > > > > > >          \sa ColourGains
> > > > > > > > > > > +        \sa ColourTemperature
> > > > > > > > > > >
> > > > > > > > > > >    # AwbMode needs further attention:
> > > > > > > > > > >    # - Auto-generate max enum value.
> > > > > > > > > > > @@ -309,13 +312,24 @@ controls:
> > > > > > > > > > >          disabled.
> > > > > > > > > > >
> > > > > > > > > > >          \sa AwbEnable
> > > > > > > > > > > +        \sa ColourTemperature
> > > > > > > > > > >        size: [2]
> > > > > > > > > > >
> > > > > > > > > > >    - ColourTemperature:
> > > > > > > > > > >        type: int32_t
> > > > > > > > > > > -      description: Report the current estimate of the colour temperature, in
> > > > > > > > > > > -        kelvin, for this frame. The ColourTemperature control can only be
> > > > > > > > > > > -        returned in metadata.
> > > > > > > > > > > +      description: |
> > > > > > > > > > > +        Report the current estimate of the colour temperature, in kelvin, for
> > > > > > > > > > > +        this frame. An implementation may also allow this control to be set when
> > > > > > > > > >
> > > > > > > > > > s/also //
> > > > > > > > > >
> > > > > > > > > > > +        AWB is disabled. In that case ColourGains and the ColourCorrectionMatrix
> > > > > > > > > > > +        get set accordingly. If either ColourGains or ColourCorrectionMatrix are
> > > > > > > > > > > +        specified at the same time, they take precedence.
> > > > > > > > > >
> > > > > > > > > > maybe "they take precedence, and the ColourTemperature is ignored" ? Or,
> > > > > > > > > > if an application sets ColourTemperature and ColourGains but not
> > > > > > > > > > ColourCorrectionMatrix, do you expect the implementation to apply the
> > > > > > > > > > requested ColourGains and set ColourCorrectionMatrix based on the
> > > > > > > > > > temperature ?
> > > > > > > > >
> > > > > > > > > The latter is exactly what happens. The following table lists the
> > > > > > > > > possible options:
> > > > > > > > >
> > > > > > > > > CT -> CG(CT), CCM(CT)
> > > > > > > > > CT, CG -> CG, CCM(CT)
> > > > > > > > > CT, CCM -> CG(CT), CCM
> > > > > > > > > CT, CG, CCM -> CG, CCM
> > > > > > > >
> > > > > > > > David, is this the behaviour you would also expect for Raspberry Pi ?
> > > > > >
> > > > > > I'm guessing the question here is really what to do if an application
> > > > > > sets both CT and CG together? The other cases seem fairly
> > > > > > uncontroversial (?).
> > > > >
> > > > > As far as I understand, for the rkisp1, the colour gains and the CCM are
> > > > > both calculated based on the colour temperature. The case where the
> > > > > application sets CT and CG is conceptually as problematic as the case
> > > > > where it sets CT and CCM. Stefan, is that correct ?
> > > > >
> > > > > > For us, I'm not sure it really makes much sense to supply both CT and
> > > > > > CG at once. When someone sets CG, the algorithm estimates the CT and
> > > > > > passes this to other algorithms, like lens shading and CCM. (So we
> > > > > > actually have a "CG -> CG, CT(CG), CCM(CT)" kind of case going on.)
> > > > >
> > > > > When an application sets CG, does the algorithm estimate CT from the
> > > > > stats, or from the CG alone for RPi ? Stefan, how about your plans for
> > > > > rkisp1 ?
> > > > 
> > > > When an application sets manual CGs, the algorithm estimates the CT
> > > > from the CT-curve in the tuning directly.
> > > 
> > > I'll try to recap what we have (hopefully) agreed on so far.
> > > 
> > > OK, so in manual AWB mode, CT and CG are interchangeable, one will be
> > > calculated from the other based on the tuning data, without taking
> > > statistics into account. As this is a pure software implementation, if
> > > both controls are specified, we can freely specify which one takes
> > > precedence, and this can be applied to all platforms. I have a
> > > preference for making the gains take precedence (as Stefan did in v5) as
> > > they provide more precise control.
> > 
> > As written in the next paragraph, I propose for no precedence between CG
> > and CT at all as we would unnecessarily limit our options.
> > 
> > > In auto AWB mode, CG and CT are both calculated by the AWB algorithm and
> > > any value set through controls is ignored.
> > > 
> > > So far, so good ?
> > > 
> > > The next question is how to handle CCM. Auto mode is easy, CCM is
> > > computed automatically, and any value set through controls is ignored.
> > > In manual mode, if CCM is set in a request, its value should be applied.
> > > What if a request contains CG or CT and no CCM ? Would CCM be computed
> > > by the AWB algorithm (in manual mode), or its previous value retained ?
> > 
> > I prepared a new update to the controls documentation, that I'll post
> > shortly. The proposal there is (for manual mode only):
> > 
> > - CG updates CT if CT is not set.
> > - CT updates CG if CG is not set.
> > - CT updates CCM if CCM is not set (Which could be triggered by the CG ->
> >   CT -> CCM chain)
> > 
> > That seems to be easiest to explain at the moment captures most use
> > cases.
> > 
> > > > > > When I add this new control, it will calculate CG from the calibrated
> > > > > > colour temperature curve in the camera tuning and use those, and pass
> > > > > > the CT to those other algorithms (so like the first row in the table).
> > > > >
> > > > > That's the main use, and I think we all agree on the behaviour. It seems
> > > > > quite uncontroversial.
> > > > >
> > > > > > I don't think I particularly want to implement cases where it takes a
> > > > > > CG value, uses them, and also a random CT which it then passes on?
> > > > > > Possibly I'd rather leave these cases (where we have both CT and CG on
> > > > > > the LHS) as either "implementation dependent" or just "undefined", and
> > > > > > recommend setting one or other.
> > > > >
> > > > > I dislike implementation-dependent behaviours if we can avoid them, at
> > > > > least in cases that we consider valid use cases. Is there a valid use
> > > > > case for setting CT along with CG or CCM ? It sounds to me like there
> > > > > wouldn't be one for RPi. Stefan, how about you ?
> > > > 
> > > > I don't think RPi has a use case that requires the CT and CGs to be both set.
> > > > 
> > > > > > Does that help or just confuse further?
> > > > >
> > > > > Let's see how the discussion progresses :-) Thank you for your input.
> > > > >
> > > > > > > > > Do you have a nice sentence for that?
> > > > > > > >
> > > > > > > > /me checks... I have a set of French proverbs, but none of the seem very
> > > > > > > > appropriate. Sorry :-)
> > > > > > >
> > > > > > > What about "If ColourGains and ColourTemperature are specified at the
> > > > > > > same time, ColourGains takes precedence. The same applies to
> > > > > > > ColourCorrectionMatrix."?
> > > > > > >
> > > > > > > We can discuss the final wording after feedback from David.
> > > > > > >
> > > > > > > > > > > +
> > > > > > > > > > > +        The metadata will only report measured colour temperature values when
> > > > > > > > > > > +        available, even if set manually.
> > > > > > > > > >
> > > > > > > > > > I'm not sure to understand this.
> > > > > > > > >
> > > > > > > > > This is based on the comment from Kieran:
> > > > > > > > > https://patchwork.libcamera.org/patch/20771/#30590 He wanted to prepare
> > > > > > > > > for cases (RPi) where no temperature gets estimated. Only measurements
> > > > > > > > > are returned in metadata. Manually set temperature is not reflected in
> > > > > > > > > the metadata. This has the nice side effect, that you can set
> > > > > > > > > AwbEnable=false, and still get temperature estimations in the metadata.
> > > > > > > >
> > > > > > > > This means that whether or not the estimated colour temperature will be
> > > > > > > > returned in metadata will be platform-dependent. Can we avoid that ? It
> > > > > > > > makes writing portable applications much more difficult.
> > > > > > > >
> > > > > > > > My other concern is that metadata is supposed to report the setting
> > > > > > > > applied to a frame. The general rule is that, if a control can be set,
> > > > > > > > the value that has been set for a frame is reported in metadata. There
> > > > > > > > are exception for trigger-like controls. As this example clearly shows,
> > > > > > > > having multiple controls that ultimately set the same values is also
> > > > > > > > problematic from this point of view. Do we need to set a rule that
> > > > > > > > higher-level controls that get translated to lower-level controls are
> > > > > > > > never reported in metadata ?
> > > > > > > >
> > > > > > > > If we do that, then we'll have ColourTemperature as a control being
> > > > > > > > defined differently from ColourTemperature as metadata. I'm not sure I
> > > > > > > > like it much. Should we have two different controls ?
> > > > > > >
> > > > > > > We could split that to "MeasuredColourTemperature" and
> > > > > > > "AppliedColorTemperature". But there are always cases where one of them
> > > > > > > (or both) is not available (as discussed on Patch 3). I think on rkisp
> > > > > > > we could ensure that MeasuredColourTemperature is always available and
> > > > > > > contains "something" as the statistics are always available. But in the
> > > > > > > end as a user I'd prefer to know when the algorithm failed to deduce a
> > > > > > > valid colour temperature.
> > > > >
> > > > > If the algorithm failed to estimate the colour temperature, that should
> > > > > be indicated by the absence of an estimated colour temperature in
> > > > > metadata.
> > > > >
> > > > > David, why do you (if I understand correctly) stop estimating the colour
> > > > > temperature from the statistics in manual AWB mode ?
> > > > 
> > > > I think it's to keep things consistent.  The CT-curve in the tuning
> > > > file is taken as the canonical truth. So if manual CGs are applied,
> > > > and assuming the users know what they are doing(!), we return a simple
> > > > lookup without going through all the computations again.  Of course,
> > > > this is simple enough to change in our code if the need arises.
> > > 
> > > I'm fine with that behaviour, but I would like to keep the metadata
> > > behaviour consistent between platforms.
> > > 
> > > For auto-mode, I think we all agree that the CG, CT and CCM metadata
> > > will report the values computed by the AWB algorithm (please wave if
> > > you disagree).
> > > 
> > > For manual mode, we've discussed two different behaviours that apply to
> > > CG, CT and CCM:
> > > 
> > > - Report the controls that are applied to the device. This matches the
> > >   standard libcamera metadata behaviour.
> > > 
> > > - Let the AWB algorithm continue to process statistics, and report the
> > >   estimated values. As far as I understand, this was requested for CT
> > >   estimation only, not for CG or CCM estimation.
> > > 
> > > While I understand that continuous CT estimation in manual mode can be
> > > tempting, I think it would require more discussions to specify it
> > > unambiguously. Stefan, Kieran, do you have a use case for this now, or
> > > is this something you considered as a nice-to-have feature ?
> > 
> > The discussion roughly went as follows:
> > 
> > There are valid cases for both colour temperatures. The one from the
> > statistics engine (measuredTemp) would be very useful to do any manual
> > regulation (outside of libcamera). The one used in the ISP for
> > processing the frame at hand (usedTemp) is useful to store in image
> > metadata or similar things. But for none of them there is a hard use
> > case.
> > 
> > The issue with usedTemp is that it is not well defined in manual mode.
> > At the time this was discussed we also had no way on rkisp1 to map from
> > CG to CT. As you lean towards that value I propose the following:
> > 
> > CT: usedTemp = CT, correct
> > CG: usedTemp = CT(CG), correct (now possible on rkisp1 also)
> > CT,CG: usedTemp = CT, incorrect because CG not taken into account but best
> > effort
> > CCM: usedTemp is unchanged, incorrect but best effort
> > 
> > I think we can live with that incorrectness as it only affects corner
> > cases.
> > 
> > For the measuredTemp we can easily introduce a MeasuredColourTemperature
> > metadata at a later stage.
> > 
> > > > > > > > > > > +
> > > > > > > > > > > +        \sa AwbEnable
> > > > > > > > > > > +        \sa ColourCorrectionMatrix
> > > > > > > > > > > +        \sa ColourGains
> > > > > > > > > > >
> > > > > > > > > > >    - Saturation:
> > > > > > > > > > >        type: float
> > > > > > > > > > > @@ -365,6 +379,8 @@ controls:
> > > > > > > > > > >          transformation. The 3x3 matrix is stored in conventional reading
> > > > > > > > > > >          order in an array of 9 floating point values.
> > > > > > > > > > >
> > > > > > > > > > > +        \sa AwbEnable
> > > > > > > > > > > +        \sa ColourTemperature
> > > > > > > > > > >        size: [3,3]
> > > > > > > > > > >
> > > > > > > > > > >    - ScalerCrop: