[libcamera-devel,v10,2/3] libcamera: raspberrypi: Add control of sensor vblanking

10679 diff mbox series

Add support for setting V4L2_CID_VBLANK appropriately when setting
V4L2_CID_EXPOSURE. This will allow adaptive framerates during
viewfinder use cases (e.g. when the exposure time goes above 33ms, we
can reduce the framerate to lower than 30fps).

The minimum and maximum frame durations are provided via libcamera
controls, and will prioritise exposure time limits over any AGC request.

V4L2_CID_VBLANK is controlled through the staggered writer, just like
the exposure and gain controls.

Signed-off-by: Naushir Patuck <naush@raspberrypi.com>
Reviewed-by: David Plowman <david.plowman@raspberrypi.com>
Tested-by: David Plowman <david.plowman@raspberrypi.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
---
 include/libcamera/ipa/raspberrypi.h           |  1 +
 src/ipa/raspberrypi/cam_helper.cpp            | 35 ++++++++++++-
 src/ipa/raspberrypi/cam_helper.hpp            | 15 +++++-
 src/ipa/raspberrypi/cam_helper_imx219.cpp     | 13 ++++-
 src/ipa/raspberrypi/cam_helper_imx477.cpp     | 11 +++-
 src/ipa/raspberrypi/cam_helper_ov5647.cpp     | 11 +++-
 src/ipa/raspberrypi/raspberrypi.cpp           | 52 ++++++++++++++++---
 .../pipeline/raspberrypi/raspberrypi.cpp      |  3 +-
 8 files changed, 127 insertions(+), 14 deletions(-)

On 18/12/2020 10:06, Naushir Patuck wrote:
> Add support for setting V4L2_CID_VBLANK appropriately when setting
> V4L2_CID_EXPOSURE. This will allow adaptive framerates during
> viewfinder use cases (e.g. when the exposure time goes above 33ms, we
> can reduce the framerate to lower than 30fps).
> 
> The minimum and maximum frame durations are provided via libcamera
> controls, and will prioritise exposure time limits over any AGC request.
> 
> V4L2_CID_VBLANK is controlled through the staggered writer, just like
> the exposure and gain controls.
> 
> Signed-off-by: Naushir Patuck <naush@raspberrypi.com>
> Reviewed-by: David Plowman <david.plowman@raspberrypi.com>
> Tested-by: David Plowman <david.plowman@raspberrypi.com>
> Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
> ---
>  include/libcamera/ipa/raspberrypi.h           |  1 +
>  src/ipa/raspberrypi/cam_helper.cpp            | 35 ++++++++++++-
>  src/ipa/raspberrypi/cam_helper.hpp            | 15 +++++-
>  src/ipa/raspberrypi/cam_helper_imx219.cpp     | 13 ++++-
>  src/ipa/raspberrypi/cam_helper_imx477.cpp     | 11 +++-
>  src/ipa/raspberrypi/cam_helper_ov5647.cpp     | 11 +++-
>  src/ipa/raspberrypi/raspberrypi.cpp           | 52 ++++++++++++++++---
>  .../pipeline/raspberrypi/raspberrypi.cpp      |  3 +-
>  8 files changed, 127 insertions(+), 14 deletions(-)
> 
> diff --git a/include/libcamera/ipa/raspberrypi.h b/include/libcamera/ipa/raspberrypi.h
> index 01fe5abc..1de36039 100644
> --- a/include/libcamera/ipa/raspberrypi.h
> +++ b/include/libcamera/ipa/raspberrypi.h
> @@ -65,6 +65,7 @@ static const ControlInfoMap Controls = {
>  	{ &controls::Sharpness, ControlInfo(0.0f, 16.0f, 1.0f) },
>  	{ &controls::ColourCorrectionMatrix, ControlInfo(-16.0f, 16.0f) },
>  	{ &controls::ScalerCrop, ControlInfo(Rectangle{}, Rectangle(65535, 65535, 65535, 65535), Rectangle{}) },
> +	{ &controls::FrameDurations, ControlInfo(1000, 1 000 000 000) },

Perhaps we should define some human readable $bignumbers to ensure we
don't mis-represent or mis-calculate large numbers like that.

Or use some chrono class to be able to express the value in readable
terms, but store it appropriately. Of course then it gets more difficult
to handle that in the Control I think ...

But anyway, not in this patch.

>  };
>  
>  } /* namespace RPi */
> diff --git a/src/ipa/raspberrypi/cam_helper.cpp b/src/ipa/raspberrypi/cam_helper.cpp
> index 6efa0d7f..018c17b9 100644
> --- a/src/ipa/raspberrypi/cam_helper.cpp
> +++ b/src/ipa/raspberrypi/cam_helper.cpp
> @@ -34,8 +34,10 @@ CamHelper *CamHelper::Create(std::string const &cam_name)
>  	return nullptr;
>  }
>  
> -CamHelper::CamHelper(MdParser *parser)
> -	: parser_(parser), initialized_(false)
> +CamHelper::CamHelper(MdParser *parser, unsigned int maxFrameLength,
> +		     unsigned int frameIntegrationDiff)
> +	: parser_(parser), initialized_(false), maxFrameLength_(maxFrameLength),
> +	  frameIntegrationDiff_(frameIntegrationDiff)
>  {
>  }
>  
> @@ -56,6 +58,35 @@ double CamHelper::Exposure(uint32_t exposure_lines) const
>  	return exposure_lines * mode_.line_length / 1000.0;
>  }
>  
> +uint32_t CamHelper::GetVBlanking(double &exposure, double minFrameDuration,
> +				 double maxFrameDuration) const
> +{
> +	uint32_t frameLengthMin, frameLengthMax, vblank;
> +	uint32_t exposureLines = ExposureLines(exposure);
> +
> +	assert(initialized_);
> +
> +	/*
> +	 * Clip frame length by the frame duration range and the maximum allowable

Clip? or Clamp? Doesn't really matter though ;-) both make sense.

> +	 * value in the sensor, given by maxFrameLength_.
> +	 */
> +	frameLengthMin = std::clamp<uint32_t>(1e3 * minFrameDuration / mode_.line_length,
> +					      mode_.height, maxFrameLength_);
> +	frameLengthMax = std::clamp<uint32_t>(1e3 * maxFrameDuration / mode_.line_length,
> +					      mode_.height, maxFrameLength_);
> +	/*
> +	 * Limit the exposure to the maximum frame duration requested, and
> +	 * re-calculate if it has been clipped.
> +	 */
> +	exposureLines = std::min(frameLengthMax - frameIntegrationDiff_, exposureLines);
> +	exposure = Exposure(exposureLines);
> +
> +	/* Limit the vblank to the range allowed by the frame length limits. */
> +	vblank = std::clamp(exposureLines + frameIntegrationDiff_,
> +			    frameLengthMin, frameLengthMax) - mode_.height;
> +	return vblank;
> +}
> +
>  void CamHelper::SetCameraMode(const CameraMode &mode)
>  {
>  	mode_ = mode;
> diff --git a/src/ipa/raspberrypi/cam_helper.hpp b/src/ipa/raspberrypi/cam_helper.hpp
> index 044c2866..b1739a57 100644
> --- a/src/ipa/raspberrypi/cam_helper.hpp
> +++ b/src/ipa/raspberrypi/cam_helper.hpp
> @@ -62,12 +62,15 @@ class CamHelper
>  {
>  public:
>  	static CamHelper *Create(std::string const &cam_name);
> -	CamHelper(MdParser *parser);
> +	CamHelper(MdParser *parser, unsigned int maxFrameLength,
> +		  unsigned int frameIntegrationDiff);
>  	virtual ~CamHelper();
>  	void SetCameraMode(const CameraMode &mode);
>  	MdParser &Parser() const { return *parser_; }
>  	uint32_t ExposureLines(double exposure_us) const;
>  	double Exposure(uint32_t exposure_lines) const; // in us
> +	virtual uint32_t GetVBlanking(double &exposure_us, double minFrameDuration,
> +				      double maxFrameDuration) const;
>  	virtual uint32_t GainCode(double gain) const = 0;
>  	virtual double Gain(uint32_t gain_code) const = 0;
>  	virtual void GetDelays(int &exposure_delay, int &gain_delay) const;
> @@ -76,10 +79,20 @@ public:
>  	virtual unsigned int HideFramesModeSwitch() const;
>  	virtual unsigned int MistrustFramesStartup() const;
>  	virtual unsigned int MistrustFramesModeSwitch() const;
> +
>  protected:
>  	MdParser *parser_;
>  	CameraMode mode_;
> +
> +private:
>  	bool initialized_;
> +	/* Largest possible frame length, in units of lines. */
> +	unsigned int maxFrameLength_;
> +	/*
> +	 * Smallest difference between the frame length and integration time,
> +	 * in units of lines.
> +	 */
> +	unsigned int frameIntegrationDiff_;
>  };
>  
>  // This is for registering camera helpers with the system, so that the
> diff --git a/src/ipa/raspberrypi/cam_helper_imx219.cpp b/src/ipa/raspberrypi/cam_helper_imx219.cpp
> index db8ab879..8688ec09 100644
> --- a/src/ipa/raspberrypi/cam_helper_imx219.cpp
> +++ b/src/ipa/raspberrypi/cam_helper_imx219.cpp
> @@ -49,13 +49,22 @@ public:
>  	double Gain(uint32_t gain_code) const override;
>  	unsigned int MistrustFramesModeSwitch() const override;
>  	bool SensorEmbeddedDataPresent() const override;
> +
> +private:
> +	/*
> +	 * Smallest difference between the frame length and integration time,
> +	 * in units of lines.
> +	 */
> +	static constexpr int frameIntegrationDiff = 4;
> +	/* Largest possible frame length, in units of lines. */
> +	static constexpr int maxFrameLength = 0xffff;
>  };
>  
>  CamHelperImx219::CamHelperImx219()
>  #if ENABLE_EMBEDDED_DATA
> -	: CamHelper(new MdParserImx219())
> +	: CamHelper(new MdParserImx219(), maxFrameLength, frameIntegrationDiff)
>  #else
> -	: CamHelper(new MdParserRPi())
> +	: CamHelper(new MdParserRPi(), maxFrameLength, frameIntegrationDiff)
>  #endif
>  {
>  }
> diff --git a/src/ipa/raspberrypi/cam_helper_imx477.cpp b/src/ipa/raspberrypi/cam_helper_imx477.cpp
> index 0e896ac7..53961310 100644
> --- a/src/ipa/raspberrypi/cam_helper_imx477.cpp
> +++ b/src/ipa/raspberrypi/cam_helper_imx477.cpp
> @@ -38,10 +38,19 @@ public:
>  	uint32_t GainCode(double gain) const override;
>  	double Gain(uint32_t gain_code) const override;
>  	bool SensorEmbeddedDataPresent() const override;
> +
> +private:
> +	/*
> +	 * Smallest difference between the frame length and integration time,
> +	 * in units of lines.
> +	 */
> +	static constexpr int frameIntegrationDiff = 22;
> +	/* Largest possible frame length, in units of lines. */
> +	static constexpr int maxFrameLength = 0xffdc;
>  };
>  
>  CamHelperImx477::CamHelperImx477()
> -	: CamHelper(new MdParserImx477())
> +	: CamHelper(new MdParserImx477(), maxFrameLength, frameIntegrationDiff)
>  {
>  }
>  
> diff --git a/src/ipa/raspberrypi/cam_helper_ov5647.cpp b/src/ipa/raspberrypi/cam_helper_ov5647.cpp
> index 0b841cd1..2bd8a754 100644
> --- a/src/ipa/raspberrypi/cam_helper_ov5647.cpp
> +++ b/src/ipa/raspberrypi/cam_helper_ov5647.cpp
> @@ -23,6 +23,15 @@ public:
>  	unsigned int HideFramesModeSwitch() const override;
>  	unsigned int MistrustFramesStartup() const override;
>  	unsigned int MistrustFramesModeSwitch() const override;
> +
> +private:
> +	/*
> +	 * Smallest difference between the frame length and integration time,
> +	 * in units of lines.
> +	 */
> +	static constexpr int frameIntegrationDiff = 4;
> +	/* Largest possible frame length, in units of lines. */
> +	static constexpr int maxFrameLength = 0xffff;
>  };
>  
>  /*
> @@ -31,7 +40,7 @@ public:
>   */
>  
>  CamHelperOv5647::CamHelperOv5647()
> -	: CamHelper(new MdParserRPi())
> +	: CamHelper(new MdParserRPi(), maxFrameLength, frameIntegrationDiff)
>  {
>  }
>  
> diff --git a/src/ipa/raspberrypi/raspberrypi.cpp b/src/ipa/raspberrypi/raspberrypi.cpp
> index d087b07e..d309536b 100644
> --- a/src/ipa/raspberrypi/raspberrypi.cpp
> +++ b/src/ipa/raspberrypi/raspberrypi.cpp
> @@ -58,6 +58,8 @@ namespace libcamera {
>  /* Configure the sensor with these values initially. */
>  constexpr double DefaultAnalogueGain = 1.0;
>  constexpr unsigned int DefaultExposureTime = 20000;
> +constexpr double defaultMinFrameDuration = 1e6 / 30.0;
> +constexpr double defaultMaxFrameDuration = 1e6 / 0.01;
>  
>  LOG_DEFINE_CATEGORY(IPARPI)
>  
> @@ -150,6 +152,9 @@ private:
>  
>  	/* Distinguish the first camera start from others. */
>  	bool firstStart_;
> +
> +	/* Frame duration (1/fps) given in microseconds. */
> +	double minFrameDuration_, maxFrameDuration_;

Hrm, there's nothing syntactically wrong with this - but I don't think
we've used multiple definitions on a single line anywhere else?

But this is src/ipa/raspberrypi ... so I think you might get away with
it :-)

>  };
>  
>  int IPARPi::init(const IPASettings &settings)
> @@ -332,7 +337,8 @@ void IPARPi::configure(const CameraSensorInfo &sensorInfo,
>  		sensorMetadata = helper_->SensorEmbeddedDataPresent();
>  
>  		result->data.push_back(gainDelay);
> -		result->data.push_back(exposureDelay);
> +		result->data.push_back(exposureDelay); /* For EXPOSURE ctrl */
> +		result->data.push_back(exposureDelay); /* For VBLANK ctrl */
>  		result->data.push_back(sensorMetadata);
>  
>  		result->operation |= RPi::IPA_CONFIG_STAGGERED_WRITE;
> @@ -377,6 +383,9 @@ void IPARPi::configure(const CameraSensorInfo &sensorInfo,
>  		controller_.Initialise();
>  		controllerInit_ = true;
>  
> +		minFrameDuration_ = defaultMinFrameDuration;
> +		maxFrameDuration_ = defaultMaxFrameDuration;
> +
>  		/* Supply initial values for gain and exposure. */
>  		ControlList ctrls(sensorCtrls_);
>  		AgcStatus agcStatus;
> @@ -524,7 +533,8 @@ bool IPARPi::validateSensorControls()
>  {
>  	static const uint32_t ctrls[] = {
>  		V4L2_CID_ANALOGUE_GAIN,
> -		V4L2_CID_EXPOSURE
> +		V4L2_CID_EXPOSURE,
> +		V4L2_CID_VBLANK

Should we keep a comma on the end so additions don't require a previous
line replacement?

>  	};
>  
>  	for (auto c : ctrls) {
> @@ -804,6 +814,24 @@ void IPARPi::queueRequest(const ControlList &controls)
>  			break;
>  		}
>  
> +		case controls::FRAME_DURATIONS: {
> +			auto frameDurations = ctrl.second.get<Span<const int64_t>>();
> +
> +			/* This will be applied once AGC recalculations occur. */
> +			minFrameDuration_ = frameDurations[0] ? frameDurations[0] : defaultMinFrameDuration;
> +			maxFrameDuration_ = frameDurations[1] ? frameDurations[1] : defaultMaxFrameDuration;
> +
> +			/*
> +			 * \todo The values returned in the metadata below must be
> +			 * correctly clipped by what the sensor mode supports and
> +			 * what the AGC exposure mode or manual shutter speed limits
> +			 */
> +			libcameraMetadata_.set(controls::FrameDurations,
> +					       { static_cast<int64_t>(minFrameDuration_),
> +						 static_cast<int64_t>(maxFrameDuration_) });
> +			break;
> +		}
> +
>  		default:
>  			LOG(IPARPI, Warning)
>  				<< "Ctrl " << controls::controls.at(ctrl.first)->name()
> @@ -962,15 +990,27 @@ void IPARPi::applyAWB(const struct AwbStatus *awbStatus, ControlList &ctrls)
>  void IPARPi::applyAGC(const struct AgcStatus *agcStatus, ControlList &ctrls)
>  {
>  	int32_t gainCode = helper_->GainCode(agcStatus->analogue_gain);
> -	int32_t exposureLines = helper_->ExposureLines(agcStatus->shutter_time);
>  
> -	LOG(IPARPI, Debug) << "Applying AGC Exposure: " << agcStatus->shutter_time
> -			   << " (Shutter lines: " << exposureLines << ") Gain: "
> +	/* GetVBlanking might clip exposure time to the fps limits. */
> +	double exposure = agcStatus->shutter_time;
> +	int32_t vblanking = helper_->GetVBlanking(exposure, minFrameDuration_,
> +						  maxFrameDuration_);
> +	int32_t exposureLines = helper_->ExposureLines(exposure);
> +
> +	LOG(IPARPI, Debug) << "Applying AGC Exposure: " << exposure
> +			   << " (Shutter lines: " << exposureLines << ", AGC requested "
> +			   << agcStatus->shutter_time << ") Gain: "
>  			   << agcStatus->analogue_gain << " (Gain Code: "
>  			   << gainCode << ")";
>  
> -	ctrls.set(V4L2_CID_ANALOGUE_GAIN, gainCode);
> +	/*
> +	 * Due to the behavior of V4L2, the current value of VBLANK could clip the
> +	 * exposure time without us knowing. The next time though this function should

The next time? You mean this only happens on the first call through? or
something else?


Nothing blocking there that I see though.

Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

> +	 * clip exposure correctly.
> +	 */
> +	ctrls.set(V4L2_CID_VBLANK, vblanking);
>  	ctrls.set(V4L2_CID_EXPOSURE, exposureLines);
> +	ctrls.set(V4L2_CID_ANALOGUE_GAIN, gainCode);
>  }
>  
>  void IPARPi::applyDG(const struct AgcStatus *dgStatus, ControlList &ctrls)
> diff --git a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> index 7a5f5881..252cab64 100644
> --- a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> +++ b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> @@ -1233,7 +1233,8 @@ int RPiCameraData::configureIPA(const CameraConfiguration *config)
>  		if (!staggeredCtrl_) {
>  			staggeredCtrl_.init(unicam_[Unicam::Image].dev(),
>  					    { { V4L2_CID_ANALOGUE_GAIN, result.data[resultIdx++] },
> -					      { V4L2_CID_EXPOSURE, result.data[resultIdx++] } });
> +					      { V4L2_CID_EXPOSURE, result.data[resultIdx++] },
> +					      { V4L2_CID_VBLANK, result.data[resultIdx++] } });
>  			sensorMetadata_ = result.data[resultIdx++];
>  		}
>  	}
>

Hi Kieran,

Thank you for the review.

On Fri, 18 Dec 2020 at 13:04, Kieran Bingham <
kieran.bingham@ideasonboard.com> wrote:

>
>
> On 18/12/2020 10:06, Naushir Patuck wrote:
> > Add support for setting V4L2_CID_VBLANK appropriately when setting
> > V4L2_CID_EXPOSURE. This will allow adaptive framerates during
> > viewfinder use cases (e.g. when the exposure time goes above 33ms, we
> > can reduce the framerate to lower than 30fps).
> >
> > The minimum and maximum frame durations are provided via libcamera
> > controls, and will prioritise exposure time limits over any AGC request.
> >
> > V4L2_CID_VBLANK is controlled through the staggered writer, just like
> > the exposure and gain controls.
> >
> > Signed-off-by: Naushir Patuck <naush@raspberrypi.com>
> > Reviewed-by: David Plowman <david.plowman@raspberrypi.com>
> > Tested-by: David Plowman <david.plowman@raspberrypi.com>
> > Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
> > ---
> >  include/libcamera/ipa/raspberrypi.h           |  1 +
> >  src/ipa/raspberrypi/cam_helper.cpp            | 35 ++++++++++++-
> >  src/ipa/raspberrypi/cam_helper.hpp            | 15 +++++-
> >  src/ipa/raspberrypi/cam_helper_imx219.cpp     | 13 ++++-
> >  src/ipa/raspberrypi/cam_helper_imx477.cpp     | 11 +++-
> >  src/ipa/raspberrypi/cam_helper_ov5647.cpp     | 11 +++-
> >  src/ipa/raspberrypi/raspberrypi.cpp           | 52 ++++++++++++++++---
> >  .../pipeline/raspberrypi/raspberrypi.cpp      |  3 +-
> >  8 files changed, 127 insertions(+), 14 deletions(-)
> >
> > diff --git a/include/libcamera/ipa/raspberrypi.h
> b/include/libcamera/ipa/raspberrypi.h
> > index 01fe5abc..1de36039 100644
> > --- a/include/libcamera/ipa/raspberrypi.h
> > +++ b/include/libcamera/ipa/raspberrypi.h
> > @@ -65,6 +65,7 @@ static const ControlInfoMap Controls = {
> >       { &controls::Sharpness, ControlInfo(0.0f, 16.0f, 1.0f) },
> >       { &controls::ColourCorrectionMatrix, ControlInfo(-16.0f, 16.0f) },
> >       { &controls::ScalerCrop, ControlInfo(Rectangle{}, Rectangle(65535,
> 65535, 65535, 65535), Rectangle{}) },
> > +     { &controls::FrameDurations, ControlInfo(1000, 1 000 000 000) },
>
> Perhaps we should define some human readable $bignumbers to ensure we
> don't mis-represent or mis-calculate large numbers like that.
>
> Or use some chrono class to be able to express the value in readable
> terms, but store it appropriately. Of course then it gets more difficult
> to handle that in the Control I think ...
>
> But anyway, not in this patch.
>
> >  };
> >
> >  } /* namespace RPi */
> > diff --git a/src/ipa/raspberrypi/cam_helper.cpp
> b/src/ipa/raspberrypi/cam_helper.cpp
> > index 6efa0d7f..018c17b9 100644
> > --- a/src/ipa/raspberrypi/cam_helper.cpp
> > +++ b/src/ipa/raspberrypi/cam_helper.cpp
> > @@ -34,8 +34,10 @@ CamHelper *CamHelper::Create(std::string const
> &cam_name)
> >       return nullptr;
> >  }
> >
> > -CamHelper::CamHelper(MdParser *parser)
> > -     : parser_(parser), initialized_(false)
> > +CamHelper::CamHelper(MdParser *parser, unsigned int maxFrameLength,
> > +                  unsigned int frameIntegrationDiff)
> > +     : parser_(parser), initialized_(false),
> maxFrameLength_(maxFrameLength),
> > +       frameIntegrationDiff_(frameIntegrationDiff)
> >  {
> >  }
> >
> > @@ -56,6 +58,35 @@ double CamHelper::Exposure(uint32_t exposure_lines)
> const
> >       return exposure_lines * mode_.line_length / 1000.0;
> >  }
> >
> > +uint32_t CamHelper::GetVBlanking(double &exposure, double
> minFrameDuration,
> > +                              double maxFrameDuration) const
> > +{
> > +     uint32_t frameLengthMin, frameLengthMax, vblank;
> > +     uint32_t exposureLines = ExposureLines(exposure);
> > +
> > +     assert(initialized_);
> > +
> > +     /*
> > +      * Clip frame length by the frame duration range and the maximum
> allowable
>
> Clip? or Clamp? Doesn't really matter though ;-) both make sense.
>
> > +      * value in the sensor, given by maxFrameLength_.
> > +      */
> > +     frameLengthMin = std::clamp<uint32_t>(1e3 * minFrameDuration /
> mode_.line_length,
> > +                                           mode_.height,
> maxFrameLength_);
> > +     frameLengthMax = std::clamp<uint32_t>(1e3 * maxFrameDuration /
> mode_.line_length,
> > +                                           mode_.height,
> maxFrameLength_);
> > +     /*
> > +      * Limit the exposure to the maximum frame duration requested, and
> > +      * re-calculate if it has been clipped.
> > +      */
> > +     exposureLines = std::min(frameLengthMax - frameIntegrationDiff_,
> exposureLines);
> > +     exposure = Exposure(exposureLines);
> > +
> > +     /* Limit the vblank to the range allowed by the frame length
> limits. */
> > +     vblank = std::clamp(exposureLines + frameIntegrationDiff_,
> > +                         frameLengthMin, frameLengthMax) - mode_.height;
> > +     return vblank;
> > +}
> > +
> >  void CamHelper::SetCameraMode(const CameraMode &mode)
> >  {
> >       mode_ = mode;
> > diff --git a/src/ipa/raspberrypi/cam_helper.hpp
> b/src/ipa/raspberrypi/cam_helper.hpp
> > index 044c2866..b1739a57 100644
> > --- a/src/ipa/raspberrypi/cam_helper.hpp
> > +++ b/src/ipa/raspberrypi/cam_helper.hpp
> > @@ -62,12 +62,15 @@ class CamHelper
> >  {
> >  public:
> >       static CamHelper *Create(std::string const &cam_name);
> > -     CamHelper(MdParser *parser);
> > +     CamHelper(MdParser *parser, unsigned int maxFrameLength,
> > +               unsigned int frameIntegrationDiff);
> >       virtual ~CamHelper();
> >       void SetCameraMode(const CameraMode &mode);
> >       MdParser &Parser() const { return *parser_; }
> >       uint32_t ExposureLines(double exposure_us) const;
> >       double Exposure(uint32_t exposure_lines) const; // in us
> > +     virtual uint32_t GetVBlanking(double &exposure_us, double
> minFrameDuration,
> > +                                   double maxFrameDuration) const;
> >       virtual uint32_t GainCode(double gain) const = 0;
> >       virtual double Gain(uint32_t gain_code) const = 0;
> >       virtual void GetDelays(int &exposure_delay, int &gain_delay) const;
> > @@ -76,10 +79,20 @@ public:
> >       virtual unsigned int HideFramesModeSwitch() const;
> >       virtual unsigned int MistrustFramesStartup() const;
> >       virtual unsigned int MistrustFramesModeSwitch() const;
> > +
> >  protected:
> >       MdParser *parser_;
> >       CameraMode mode_;
> > +
> > +private:
> >       bool initialized_;
> > +     /* Largest possible frame length, in units of lines. */
> > +     unsigned int maxFrameLength_;
> > +     /*
> > +      * Smallest difference between the frame length and integration
> time,
> > +      * in units of lines.
> > +      */
> > +     unsigned int frameIntegrationDiff_;
> >  };
> >
> >  // This is for registering camera helpers with the system, so that the
> > diff --git a/src/ipa/raspberrypi/cam_helper_imx219.cpp
> b/src/ipa/raspberrypi/cam_helper_imx219.cpp
> > index db8ab879..8688ec09 100644
> > --- a/src/ipa/raspberrypi/cam_helper_imx219.cpp
> > +++ b/src/ipa/raspberrypi/cam_helper_imx219.cpp
> > @@ -49,13 +49,22 @@ public:
> >       double Gain(uint32_t gain_code) const override;
> >       unsigned int MistrustFramesModeSwitch() const override;
> >       bool SensorEmbeddedDataPresent() const override;
> > +
> > +private:
> > +     /*
> > +      * Smallest difference between the frame length and integration
> time,
> > +      * in units of lines.
> > +      */
> > +     static constexpr int frameIntegrationDiff = 4;
> > +     /* Largest possible frame length, in units of lines. */
> > +     static constexpr int maxFrameLength = 0xffff;
> >  };
> >
> >  CamHelperImx219::CamHelperImx219()
> >  #if ENABLE_EMBEDDED_DATA
> > -     : CamHelper(new MdParserImx219())
> > +     : CamHelper(new MdParserImx219(), maxFrameLength,
> frameIntegrationDiff)
> >  #else
> > -     : CamHelper(new MdParserRPi())
> > +     : CamHelper(new MdParserRPi(), maxFrameLength,
> frameIntegrationDiff)
> >  #endif
> >  {
> >  }
> > diff --git a/src/ipa/raspberrypi/cam_helper_imx477.cpp
> b/src/ipa/raspberrypi/cam_helper_imx477.cpp
> > index 0e896ac7..53961310 100644
> > --- a/src/ipa/raspberrypi/cam_helper_imx477.cpp
> > +++ b/src/ipa/raspberrypi/cam_helper_imx477.cpp
> > @@ -38,10 +38,19 @@ public:
> >       uint32_t GainCode(double gain) const override;
> >       double Gain(uint32_t gain_code) const override;
> >       bool SensorEmbeddedDataPresent() const override;
> > +
> > +private:
> > +     /*
> > +      * Smallest difference between the frame length and integration
> time,
> > +      * in units of lines.
> > +      */
> > +     static constexpr int frameIntegrationDiff = 22;
> > +     /* Largest possible frame length, in units of lines. */
> > +     static constexpr int maxFrameLength = 0xffdc;
> >  };
> >
> >  CamHelperImx477::CamHelperImx477()
> > -     : CamHelper(new MdParserImx477())
> > +     : CamHelper(new MdParserImx477(), maxFrameLength,
> frameIntegrationDiff)
> >  {
> >  }
> >
> > diff --git a/src/ipa/raspberrypi/cam_helper_ov5647.cpp
> b/src/ipa/raspberrypi/cam_helper_ov5647.cpp
> > index 0b841cd1..2bd8a754 100644
> > --- a/src/ipa/raspberrypi/cam_helper_ov5647.cpp
> > +++ b/src/ipa/raspberrypi/cam_helper_ov5647.cpp
> > @@ -23,6 +23,15 @@ public:
> >       unsigned int HideFramesModeSwitch() const override;
> >       unsigned int MistrustFramesStartup() const override;
> >       unsigned int MistrustFramesModeSwitch() const override;
> > +
> > +private:
> > +     /*
> > +      * Smallest difference between the frame length and integration
> time,
> > +      * in units of lines.
> > +      */
> > +     static constexpr int frameIntegrationDiff = 4;
> > +     /* Largest possible frame length, in units of lines. */
> > +     static constexpr int maxFrameLength = 0xffff;
> >  };
> >
> >  /*
> > @@ -31,7 +40,7 @@ public:
> >   */
> >
> >  CamHelperOv5647::CamHelperOv5647()
> > -     : CamHelper(new MdParserRPi())
> > +     : CamHelper(new MdParserRPi(), maxFrameLength,
> frameIntegrationDiff)
> >  {
> >  }
> >
> > diff --git a/src/ipa/raspberrypi/raspberrypi.cpp
> b/src/ipa/raspberrypi/raspberrypi.cpp
> > index d087b07e..d309536b 100644
> > --- a/src/ipa/raspberrypi/raspberrypi.cpp
> > +++ b/src/ipa/raspberrypi/raspberrypi.cpp
> > @@ -58,6 +58,8 @@ namespace libcamera {
> >  /* Configure the sensor with these values initially. */
> >  constexpr double DefaultAnalogueGain = 1.0;
> >  constexpr unsigned int DefaultExposureTime = 20000;
> > +constexpr double defaultMinFrameDuration = 1e6 / 30.0;
> > +constexpr double defaultMaxFrameDuration = 1e6 / 0.01;
> >
> >  LOG_DEFINE_CATEGORY(IPARPI)
> >
> > @@ -150,6 +152,9 @@ private:
> >
> >       /* Distinguish the first camera start from others. */
> >       bool firstStart_;
> > +
> > +     /* Frame duration (1/fps) given in microseconds. */
> > +     double minFrameDuration_, maxFrameDuration_;
>
> Hrm, there's nothing syntactically wrong with this - but I don't think
> we've used multiple definitions on a single line anywhere else?
>
> But this is src/ipa/raspberrypi ... so I think you might get away with
> it :-)
>
> >  };
> >
> >  int IPARPi::init(const IPASettings &settings)
> > @@ -332,7 +337,8 @@ void IPARPi::configure(const CameraSensorInfo
> &sensorInfo,
> >               sensorMetadata = helper_->SensorEmbeddedDataPresent();
> >
> >               result->data.push_back(gainDelay);
> > -             result->data.push_back(exposureDelay);
> > +             result->data.push_back(exposureDelay); /* For EXPOSURE
> ctrl */
> > +             result->data.push_back(exposureDelay); /* For VBLANK ctrl
> */
> >               result->data.push_back(sensorMetadata);
> >
> >               result->operation |= RPi::IPA_CONFIG_STAGGERED_WRITE;
> > @@ -377,6 +383,9 @@ void IPARPi::configure(const CameraSensorInfo
> &sensorInfo,
> >               controller_.Initialise();
> >               controllerInit_ = true;
> >
> > +             minFrameDuration_ = defaultMinFrameDuration;
> > +             maxFrameDuration_ = defaultMaxFrameDuration;
> > +
> >               /* Supply initial values for gain and exposure. */
> >               ControlList ctrls(sensorCtrls_);
> >               AgcStatus agcStatus;
> > @@ -524,7 +533,8 @@ bool IPARPi::validateSensorControls()
> >  {
> >       static const uint32_t ctrls[] = {
> >               V4L2_CID_ANALOGUE_GAIN,
> > -             V4L2_CID_EXPOSURE
> > +             V4L2_CID_EXPOSURE,
> > +             V4L2_CID_VBLANK
>
> Should we keep a comma on the end so additions don't require a previous
> line replacement?
>
> >       };
> >
> >       for (auto c : ctrls) {
> > @@ -804,6 +814,24 @@ void IPARPi::queueRequest(const ControlList
> &controls)
> >                       break;
> >               }
> >
> > +             case controls::FRAME_DURATIONS: {
> > +                     auto frameDurations = ctrl.second.get<Span<const
> int64_t>>();
> > +
> > +                     /* This will be applied once AGC recalculations
> occur. */
> > +                     minFrameDuration_ = frameDurations[0] ?
> frameDurations[0] : defaultMinFrameDuration;
> > +                     maxFrameDuration_ = frameDurations[1] ?
> frameDurations[1] : defaultMaxFrameDuration;
> > +
> > +                     /*
> > +                      * \todo The values returned in the metadata below
> must be
> > +                      * correctly clipped by what the sensor mode
> supports and
> > +                      * what the AGC exposure mode or manual shutter
> speed limits
> > +                      */
> > +                     libcameraMetadata_.set(controls::FrameDurations,
> > +                                            {
> static_cast<int64_t>(minFrameDuration_),
> > +
> static_cast<int64_t>(maxFrameDuration_) });
> > +                     break;
> > +             }
> > +
> >               default:
> >                       LOG(IPARPI, Warning)
> >                               << "Ctrl " << controls::controls.at
> (ctrl.first)->name()
> > @@ -962,15 +990,27 @@ void IPARPi::applyAWB(const struct AwbStatus
> *awbStatus, ControlList &ctrls)
> >  void IPARPi::applyAGC(const struct AgcStatus *agcStatus, ControlList
> &ctrls)
> >  {
> >       int32_t gainCode = helper_->GainCode(agcStatus->analogue_gain);
> > -     int32_t exposureLines =
> helper_->ExposureLines(agcStatus->shutter_time);
> >
> > -     LOG(IPARPI, Debug) << "Applying AGC Exposure: " <<
> agcStatus->shutter_time
> > -                        << " (Shutter lines: " << exposureLines << ")
> Gain: "
> > +     /* GetVBlanking might clip exposure time to the fps limits. */
> > +     double exposure = agcStatus->shutter_time;
> > +     int32_t vblanking = helper_->GetVBlanking(exposure,
> minFrameDuration_,
> > +                                               maxFrameDuration_);
> > +     int32_t exposureLines = helper_->ExposureLines(exposure);
> > +
> > +     LOG(IPARPI, Debug) << "Applying AGC Exposure: " << exposure
> > +                        << " (Shutter lines: " << exposureLines << ",
> AGC requested "
> > +                        << agcStatus->shutter_time << ") Gain: "
> >                          << agcStatus->analogue_gain << " (Gain Code: "
> >                          << gainCode << ")";
> >
> > -     ctrls.set(V4L2_CID_ANALOGUE_GAIN, gainCode);
> > +     /*
> > +      * Due to the behavior of V4L2, the current value of VBLANK could
> clip the
> > +      * exposure time without us knowing. The next time though this
> function should
>
> The next time? You mean this only happens on the first call through? or
> something else?
>

By "next time", I mean the next time you go into this function to set
exposure, it will be validated against the previous VBLANK ctrl value which
is a bit annoything.  And the cycle continues on every subsequent call to
applyAGC().  Does not matter so much, I do have a workaround for this in my
next series.

Regards,
Naush



>
>
> Nothing blocking there that I see though.
>
> Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
>
> > +      * clip exposure correctly.
> > +      */
> > +     ctrls.set(V4L2_CID_VBLANK, vblanking);
> >       ctrls.set(V4L2_CID_EXPOSURE, exposureLines);
> > +     ctrls.set(V4L2_CID_ANALOGUE_GAIN, gainCode);
> >  }
> >
> >  void IPARPi::applyDG(const struct AgcStatus *dgStatus, ControlList
> &ctrls)
> > diff --git a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > index 7a5f5881..252cab64 100644
> > --- a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > +++ b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > @@ -1233,7 +1233,8 @@ int RPiCameraData::configureIPA(const
> CameraConfiguration *config)
> >               if (!staggeredCtrl_) {
> >                       staggeredCtrl_.init(unicam_[Unicam::Image].dev(),
> >                                           { { V4L2_CID_ANALOGUE_GAIN,
> result.data[resultIdx++] },
> > -                                           { V4L2_CID_EXPOSURE,
> result.data[resultIdx++] } });
> > +                                           { V4L2_CID_EXPOSURE,
> result.data[resultIdx++] },
> > +                                           { V4L2_CID_VBLANK,
> result.data[resultIdx++] } });
> >                       sensorMetadata_ = result.data[resultIdx++];
> >               }
> >       }
> >
>
> --
> Regards
> --
> Kieran
>

Hi Naush,

Thank you for the patch.

On Fri, Dec 18, 2020 at 10:06:26AM +0000, Naushir Patuck wrote:
> Add support for setting V4L2_CID_VBLANK appropriately when setting
> V4L2_CID_EXPOSURE. This will allow adaptive framerates during
> viewfinder use cases (e.g. when the exposure time goes above 33ms, we
> can reduce the framerate to lower than 30fps).
> 
> The minimum and maximum frame durations are provided via libcamera
> controls, and will prioritise exposure time limits over any AGC request.
> 
> V4L2_CID_VBLANK is controlled through the staggered writer, just like
> the exposure and gain controls.
> 
> Signed-off-by: Naushir Patuck <naush@raspberrypi.com>
> Reviewed-by: David Plowman <david.plowman@raspberrypi.com>
> Tested-by: David Plowman <david.plowman@raspberrypi.com>
> Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
> ---
>  include/libcamera/ipa/raspberrypi.h           |  1 +
>  src/ipa/raspberrypi/cam_helper.cpp            | 35 ++++++++++++-
>  src/ipa/raspberrypi/cam_helper.hpp            | 15 +++++-
>  src/ipa/raspberrypi/cam_helper_imx219.cpp     | 13 ++++-
>  src/ipa/raspberrypi/cam_helper_imx477.cpp     | 11 +++-
>  src/ipa/raspberrypi/cam_helper_ov5647.cpp     | 11 +++-
>  src/ipa/raspberrypi/raspberrypi.cpp           | 52 ++++++++++++++++---
>  .../pipeline/raspberrypi/raspberrypi.cpp      |  3 +-
>  8 files changed, 127 insertions(+), 14 deletions(-)
> 
> diff --git a/include/libcamera/ipa/raspberrypi.h b/include/libcamera/ipa/raspberrypi.h
> index 01fe5abc..1de36039 100644
> --- a/include/libcamera/ipa/raspberrypi.h
> +++ b/include/libcamera/ipa/raspberrypi.h
> @@ -65,6 +65,7 @@ static const ControlInfoMap Controls = {
>  	{ &controls::Sharpness, ControlInfo(0.0f, 16.0f, 1.0f) },
>  	{ &controls::ColourCorrectionMatrix, ControlInfo(-16.0f, 16.0f) },
>  	{ &controls::ScalerCrop, ControlInfo(Rectangle{}, Rectangle(65535, 65535, 65535, 65535), Rectangle{}) },
> +	{ &controls::FrameDurations, ControlInfo(1000, 1000000000) },
>  };
>  
>  } /* namespace RPi */
> diff --git a/src/ipa/raspberrypi/cam_helper.cpp b/src/ipa/raspberrypi/cam_helper.cpp
> index 6efa0d7f..018c17b9 100644
> --- a/src/ipa/raspberrypi/cam_helper.cpp
> +++ b/src/ipa/raspberrypi/cam_helper.cpp
> @@ -34,8 +34,10 @@ CamHelper *CamHelper::Create(std::string const &cam_name)
>  	return nullptr;
>  }
>  
> -CamHelper::CamHelper(MdParser *parser)
> -	: parser_(parser), initialized_(false)
> +CamHelper::CamHelper(MdParser *parser, unsigned int maxFrameLength,
> +		     unsigned int frameIntegrationDiff)
> +	: parser_(parser), initialized_(false), maxFrameLength_(maxFrameLength),
> +	  frameIntegrationDiff_(frameIntegrationDiff)
>  {
>  }
>  
> @@ -56,6 +58,35 @@ double CamHelper::Exposure(uint32_t exposure_lines) const
>  	return exposure_lines * mode_.line_length / 1000.0;
>  }
>  
> +uint32_t CamHelper::GetVBlanking(double &exposure, double minFrameDuration,
> +				 double maxFrameDuration) const
> +{
> +	uint32_t frameLengthMin, frameLengthMax, vblank;
> +	uint32_t exposureLines = ExposureLines(exposure);
> +
> +	assert(initialized_);
> +
> +	/*
> +	 * Clip frame length by the frame duration range and the maximum allowable
> +	 * value in the sensor, given by maxFrameLength_.
> +	 */
> +	frameLengthMin = std::clamp<uint32_t>(1e3 * minFrameDuration / mode_.line_length,
> +					      mode_.height, maxFrameLength_);
> +	frameLengthMax = std::clamp<uint32_t>(1e3 * maxFrameDuration / mode_.line_length,
> +					      mode_.height, maxFrameLength_);
> +	/*
> +	 * Limit the exposure to the maximum frame duration requested, and
> +	 * re-calculate if it has been clipped.
> +	 */
> +	exposureLines = std::min(frameLengthMax - frameIntegrationDiff_, exposureLines);
> +	exposure = Exposure(exposureLines);
> +
> +	/* Limit the vblank to the range allowed by the frame length limits. */
> +	vblank = std::clamp(exposureLines + frameIntegrationDiff_,
> +			    frameLengthMin, frameLengthMax) - mode_.height;
> +	return vblank;
> +}
> +
>  void CamHelper::SetCameraMode(const CameraMode &mode)
>  {
>  	mode_ = mode;
> diff --git a/src/ipa/raspberrypi/cam_helper.hpp b/src/ipa/raspberrypi/cam_helper.hpp
> index 044c2866..b1739a57 100644
> --- a/src/ipa/raspberrypi/cam_helper.hpp
> +++ b/src/ipa/raspberrypi/cam_helper.hpp
> @@ -62,12 +62,15 @@ class CamHelper
>  {
>  public:
>  	static CamHelper *Create(std::string const &cam_name);
> -	CamHelper(MdParser *parser);
> +	CamHelper(MdParser *parser, unsigned int maxFrameLength,
> +		  unsigned int frameIntegrationDiff);
>  	virtual ~CamHelper();
>  	void SetCameraMode(const CameraMode &mode);
>  	MdParser &Parser() const { return *parser_; }
>  	uint32_t ExposureLines(double exposure_us) const;
>  	double Exposure(uint32_t exposure_lines) const; // in us
> +	virtual uint32_t GetVBlanking(double &exposure_us, double minFrameDuration,
> +				      double maxFrameDuration) const;
>  	virtual uint32_t GainCode(double gain) const = 0;
>  	virtual double Gain(uint32_t gain_code) const = 0;
>  	virtual void GetDelays(int &exposure_delay, int &gain_delay) const;
> @@ -76,10 +79,20 @@ public:
>  	virtual unsigned int HideFramesModeSwitch() const;
>  	virtual unsigned int MistrustFramesStartup() const;
>  	virtual unsigned int MistrustFramesModeSwitch() const;
> +
>  protected:
>  	MdParser *parser_;
>  	CameraMode mode_;
> +
> +private:
>  	bool initialized_;
> +	/* Largest possible frame length, in units of lines. */
> +	unsigned int maxFrameLength_;
> +	/*
> +	 * Smallest difference between the frame length and integration time,
> +	 * in units of lines.
> +	 */
> +	unsigned int frameIntegrationDiff_;
>  };
>  
>  // This is for registering camera helpers with the system, so that the
> diff --git a/src/ipa/raspberrypi/cam_helper_imx219.cpp b/src/ipa/raspberrypi/cam_helper_imx219.cpp
> index db8ab879..8688ec09 100644
> --- a/src/ipa/raspberrypi/cam_helper_imx219.cpp
> +++ b/src/ipa/raspberrypi/cam_helper_imx219.cpp
> @@ -49,13 +49,22 @@ public:
>  	double Gain(uint32_t gain_code) const override;
>  	unsigned int MistrustFramesModeSwitch() const override;
>  	bool SensorEmbeddedDataPresent() const override;
> +
> +private:
> +	/*
> +	 * Smallest difference between the frame length and integration time,
> +	 * in units of lines.
> +	 */
> +	static constexpr int frameIntegrationDiff = 4;
> +	/* Largest possible frame length, in units of lines. */
> +	static constexpr int maxFrameLength = 0xffff;
>  };
>  
>  CamHelperImx219::CamHelperImx219()
>  #if ENABLE_EMBEDDED_DATA
> -	: CamHelper(new MdParserImx219())
> +	: CamHelper(new MdParserImx219(), maxFrameLength, frameIntegrationDiff)
>  #else
> -	: CamHelper(new MdParserRPi())
> +	: CamHelper(new MdParserRPi(), maxFrameLength, frameIntegrationDiff)
>  #endif
>  {
>  }
> diff --git a/src/ipa/raspberrypi/cam_helper_imx477.cpp b/src/ipa/raspberrypi/cam_helper_imx477.cpp
> index 0e896ac7..53961310 100644
> --- a/src/ipa/raspberrypi/cam_helper_imx477.cpp
> +++ b/src/ipa/raspberrypi/cam_helper_imx477.cpp
> @@ -38,10 +38,19 @@ public:
>  	uint32_t GainCode(double gain) const override;
>  	double Gain(uint32_t gain_code) const override;
>  	bool SensorEmbeddedDataPresent() const override;
> +
> +private:
> +	/*
> +	 * Smallest difference between the frame length and integration time,
> +	 * in units of lines.
> +	 */
> +	static constexpr int frameIntegrationDiff = 22;
> +	/* Largest possible frame length, in units of lines. */
> +	static constexpr int maxFrameLength = 0xffdc;
>  };
>  
>  CamHelperImx477::CamHelperImx477()
> -	: CamHelper(new MdParserImx477())
> +	: CamHelper(new MdParserImx477(), maxFrameLength, frameIntegrationDiff)
>  {
>  }
>  
> diff --git a/src/ipa/raspberrypi/cam_helper_ov5647.cpp b/src/ipa/raspberrypi/cam_helper_ov5647.cpp
> index 0b841cd1..2bd8a754 100644
> --- a/src/ipa/raspberrypi/cam_helper_ov5647.cpp
> +++ b/src/ipa/raspberrypi/cam_helper_ov5647.cpp
> @@ -23,6 +23,15 @@ public:
>  	unsigned int HideFramesModeSwitch() const override;
>  	unsigned int MistrustFramesStartup() const override;
>  	unsigned int MistrustFramesModeSwitch() const override;
> +
> +private:
> +	/*
> +	 * Smallest difference between the frame length and integration time,
> +	 * in units of lines.
> +	 */
> +	static constexpr int frameIntegrationDiff = 4;
> +	/* Largest possible frame length, in units of lines. */
> +	static constexpr int maxFrameLength = 0xffff;
>  };
>  
>  /*
> @@ -31,7 +40,7 @@ public:
>   */
>  
>  CamHelperOv5647::CamHelperOv5647()
> -	: CamHelper(new MdParserRPi())
> +	: CamHelper(new MdParserRPi(), maxFrameLength, frameIntegrationDiff)
>  {
>  }
>  
> diff --git a/src/ipa/raspberrypi/raspberrypi.cpp b/src/ipa/raspberrypi/raspberrypi.cpp
> index d087b07e..d309536b 100644
> --- a/src/ipa/raspberrypi/raspberrypi.cpp
> +++ b/src/ipa/raspberrypi/raspberrypi.cpp
> @@ -58,6 +58,8 @@ namespace libcamera {
>  /* Configure the sensor with these values initially. */
>  constexpr double DefaultAnalogueGain = 1.0;
>  constexpr unsigned int DefaultExposureTime = 20000;
> +constexpr double defaultMinFrameDuration = 1e6 / 30.0;
> +constexpr double defaultMaxFrameDuration = 1e6 / 0.01;
>  
>  LOG_DEFINE_CATEGORY(IPARPI)
>  
> @@ -150,6 +152,9 @@ private:
>  
>  	/* Distinguish the first camera start from others. */
>  	bool firstStart_;
> +
> +	/* Frame duration (1/fps) given in microseconds. */
> +	double minFrameDuration_, maxFrameDuration_;
>  };
>  
>  int IPARPi::init(const IPASettings &settings)
> @@ -332,7 +337,8 @@ void IPARPi::configure(const CameraSensorInfo &sensorInfo,
>  		sensorMetadata = helper_->SensorEmbeddedDataPresent();
>  
>  		result->data.push_back(gainDelay);
> -		result->data.push_back(exposureDelay);
> +		result->data.push_back(exposureDelay); /* For EXPOSURE ctrl */
> +		result->data.push_back(exposureDelay); /* For VBLANK ctrl */
>  		result->data.push_back(sensorMetadata);
>  
>  		result->operation |= RPi::IPA_CONFIG_STAGGERED_WRITE;
> @@ -377,6 +383,9 @@ void IPARPi::configure(const CameraSensorInfo &sensorInfo,
>  		controller_.Initialise();
>  		controllerInit_ = true;
>  
> +		minFrameDuration_ = defaultMinFrameDuration;
> +		maxFrameDuration_ = defaultMaxFrameDuration;
> +
>  		/* Supply initial values for gain and exposure. */
>  		ControlList ctrls(sensorCtrls_);
>  		AgcStatus agcStatus;
> @@ -524,7 +533,8 @@ bool IPARPi::validateSensorControls()
>  {
>  	static const uint32_t ctrls[] = {
>  		V4L2_CID_ANALOGUE_GAIN,
> -		V4L2_CID_EXPOSURE
> +		V4L2_CID_EXPOSURE,
> +		V4L2_CID_VBLANK
>  	};
>  
>  	for (auto c : ctrls) {
> @@ -804,6 +814,24 @@ void IPARPi::queueRequest(const ControlList &controls)
>  			break;
>  		}
>  
> +		case controls::FRAME_DURATIONS: {
> +			auto frameDurations = ctrl.second.get<Span<const int64_t>>();
> +
> +			/* This will be applied once AGC recalculations occur. */
> +			minFrameDuration_ = frameDurations[0] ? frameDurations[0] : defaultMinFrameDuration;
> +			maxFrameDuration_ = frameDurations[1] ? frameDurations[1] : defaultMaxFrameDuration;

Should it be documented in patch 1/3 that setting the min or max to 0
will reset the limit to the default ?

Will the code behave correctly if min > max ?

> +
> +			/*
> +			 * \todo The values returned in the metadata below must be
> +			 * correctly clipped by what the sensor mode supports and
> +			 * what the AGC exposure mode or manual shutter speed limits
> +			 */
> +			libcameraMetadata_.set(controls::FrameDurations,
> +					       { static_cast<int64_t>(minFrameDuration_),
> +						 static_cast<int64_t>(maxFrameDuration_) });
> +			break;
> +		}
> +
>  		default:
>  			LOG(IPARPI, Warning)
>  				<< "Ctrl " << controls::controls.at(ctrl.first)->name()
> @@ -962,15 +990,27 @@ void IPARPi::applyAWB(const struct AwbStatus *awbStatus, ControlList &ctrls)
>  void IPARPi::applyAGC(const struct AgcStatus *agcStatus, ControlList &ctrls)
>  {
>  	int32_t gainCode = helper_->GainCode(agcStatus->analogue_gain);
> -	int32_t exposureLines = helper_->ExposureLines(agcStatus->shutter_time);
>  
> -	LOG(IPARPI, Debug) << "Applying AGC Exposure: " << agcStatus->shutter_time
> -			   << " (Shutter lines: " << exposureLines << ") Gain: "
> +	/* GetVBlanking might clip exposure time to the fps limits. */
> +	double exposure = agcStatus->shutter_time;
> +	int32_t vblanking = helper_->GetVBlanking(exposure, minFrameDuration_,
> +						  maxFrameDuration_);
> +	int32_t exposureLines = helper_->ExposureLines(exposure);
> +
> +	LOG(IPARPI, Debug) << "Applying AGC Exposure: " << exposure
> +			   << " (Shutter lines: " << exposureLines << ", AGC requested "
> +			   << agcStatus->shutter_time << ") Gain: "
>  			   << agcStatus->analogue_gain << " (Gain Code: "
>  			   << gainCode << ")";
>  
> -	ctrls.set(V4L2_CID_ANALOGUE_GAIN, gainCode);
> +	/*
> +	 * Due to the behavior of V4L2, the current value of VBLANK could clip the
> +	 * exposure time without us knowing. The next time though this function should
> +	 * clip exposure correctly.
> +	 */

This is something we should address in V4L2 (obviously not a blocker for
this series). If you could design it from scratch, what would be a good
API to configure the h/v blanking (possibly expressed as h/v active
instead of blanking) and exposure time ?

> +	ctrls.set(V4L2_CID_VBLANK, vblanking);
>  	ctrls.set(V4L2_CID_EXPOSURE, exposureLines);
> +	ctrls.set(V4L2_CID_ANALOGUE_GAIN, gainCode);
>  }
>  
>  void IPARPi::applyDG(const struct AgcStatus *dgStatus, ControlList &ctrls)
> diff --git a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> index 7a5f5881..252cab64 100644
> --- a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> +++ b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> @@ -1233,7 +1233,8 @@ int RPiCameraData::configureIPA(const CameraConfiguration *config)
>  		if (!staggeredCtrl_) {
>  			staggeredCtrl_.init(unicam_[Unicam::Image].dev(),
>  					    { { V4L2_CID_ANALOGUE_GAIN, result.data[resultIdx++] },
> -					      { V4L2_CID_EXPOSURE, result.data[resultIdx++] } });
> +					      { V4L2_CID_EXPOSURE, result.data[resultIdx++] },
> +					      { V4L2_CID_VBLANK, result.data[resultIdx++] } });
>  			sensorMetadata_ = result.data[resultIdx++];
>  		}
>  	}

Hi Laurent,

Thank you for your review feedback.

On Sun, 20 Dec 2020 at 05:52, Laurent Pinchart <
laurent.pinchart@ideasonboard.com> wrote:

> Hi Naush,
>
> Thank you for the patch.
>
> On Fri, Dec 18, 2020 at 10:06:26AM +0000, Naushir Patuck wrote:
> > Add support for setting V4L2_CID_VBLANK appropriately when setting
> > V4L2_CID_EXPOSURE. This will allow adaptive framerates during
> > viewfinder use cases (e.g. when the exposure time goes above 33ms, we
> > can reduce the framerate to lower than 30fps).
> >
> > The minimum and maximum frame durations are provided via libcamera
> > controls, and will prioritise exposure time limits over any AGC request.
> >
> > V4L2_CID_VBLANK is controlled through the staggered writer, just like
> > the exposure and gain controls.
> >
> > Signed-off-by: Naushir Patuck <naush@raspberrypi.com>
> > Reviewed-by: David Plowman <david.plowman@raspberrypi.com>
> > Tested-by: David Plowman <david.plowman@raspberrypi.com>
> > Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
> > ---
> >  include/libcamera/ipa/raspberrypi.h           |  1 +
> >  src/ipa/raspberrypi/cam_helper.cpp            | 35 ++++++++++++-
> >  src/ipa/raspberrypi/cam_helper.hpp            | 15 +++++-
> >  src/ipa/raspberrypi/cam_helper_imx219.cpp     | 13 ++++-
> >  src/ipa/raspberrypi/cam_helper_imx477.cpp     | 11 +++-
> >  src/ipa/raspberrypi/cam_helper_ov5647.cpp     | 11 +++-
> >  src/ipa/raspberrypi/raspberrypi.cpp           | 52 ++++++++++++++++---
> >  .../pipeline/raspberrypi/raspberrypi.cpp      |  3 +-
> >  8 files changed, 127 insertions(+), 14 deletions(-)
> >
> > diff --git a/include/libcamera/ipa/raspberrypi.h
> b/include/libcamera/ipa/raspberrypi.h
> > index 01fe5abc..1de36039 100644
> > --- a/include/libcamera/ipa/raspberrypi.h
> > +++ b/include/libcamera/ipa/raspberrypi.h
> > @@ -65,6 +65,7 @@ static const ControlInfoMap Controls = {
> >       { &controls::Sharpness, ControlInfo(0.0f, 16.0f, 1.0f) },
> >       { &controls::ColourCorrectionMatrix, ControlInfo(-16.0f, 16.0f) },
> >       { &controls::ScalerCrop, ControlInfo(Rectangle{}, Rectangle(65535,
> 65535, 65535, 65535), Rectangle{}) },
> > +     { &controls::FrameDurations, ControlInfo(1000, 1000000000) },
> >  };
> >
> >  } /* namespace RPi */
> > diff --git a/src/ipa/raspberrypi/cam_helper.cpp
> b/src/ipa/raspberrypi/cam_helper.cpp
> > index 6efa0d7f..018c17b9 100644
> > --- a/src/ipa/raspberrypi/cam_helper.cpp
> > +++ b/src/ipa/raspberrypi/cam_helper.cpp
> > @@ -34,8 +34,10 @@ CamHelper *CamHelper::Create(std::string const
> &cam_name)
> >       return nullptr;
> >  }
> >
> > -CamHelper::CamHelper(MdParser *parser)
> > -     : parser_(parser), initialized_(false)
> > +CamHelper::CamHelper(MdParser *parser, unsigned int maxFrameLength,
> > +                  unsigned int frameIntegrationDiff)
> > +     : parser_(parser), initialized_(false),
> maxFrameLength_(maxFrameLength),
> > +       frameIntegrationDiff_(frameIntegrationDiff)
> >  {
> >  }
> >
> > @@ -56,6 +58,35 @@ double CamHelper::Exposure(uint32_t exposure_lines)
> const
> >       return exposure_lines * mode_.line_length / 1000.0;
> >  }
> >
> > +uint32_t CamHelper::GetVBlanking(double &exposure, double
> minFrameDuration,
> > +                              double maxFrameDuration) const
> > +{
> > +     uint32_t frameLengthMin, frameLengthMax, vblank;
> > +     uint32_t exposureLines = ExposureLines(exposure);
> > +
> > +     assert(initialized_);
> > +
> > +     /*
> > +      * Clip frame length by the frame duration range and the maximum
> allowable
> > +      * value in the sensor, given by maxFrameLength_.
> > +      */
> > +     frameLengthMin = std::clamp<uint32_t>(1e3 * minFrameDuration /
> mode_.line_length,
> > +                                           mode_.height,
> maxFrameLength_);
> > +     frameLengthMax = std::clamp<uint32_t>(1e3 * maxFrameDuration /
> mode_.line_length,
> > +                                           mode_.height,
> maxFrameLength_);
> > +     /*
> > +      * Limit the exposure to the maximum frame duration requested, and
> > +      * re-calculate if it has been clipped.
> > +      */
> > +     exposureLines = std::min(frameLengthMax - frameIntegrationDiff_,
> exposureLines);
> > +     exposure = Exposure(exposureLines);
> > +
> > +     /* Limit the vblank to the range allowed by the frame length
> limits. */
> > +     vblank = std::clamp(exposureLines + frameIntegrationDiff_,
> > +                         frameLengthMin, frameLengthMax) - mode_.height;
> > +     return vblank;
> > +}
> > +
> >  void CamHelper::SetCameraMode(const CameraMode &mode)
> >  {
> >       mode_ = mode;
> > diff --git a/src/ipa/raspberrypi/cam_helper.hpp
> b/src/ipa/raspberrypi/cam_helper.hpp
> > index 044c2866..b1739a57 100644
> > --- a/src/ipa/raspberrypi/cam_helper.hpp
> > +++ b/src/ipa/raspberrypi/cam_helper.hpp
> > @@ -62,12 +62,15 @@ class CamHelper
> >  {
> >  public:
> >       static CamHelper *Create(std::string const &cam_name);
> > -     CamHelper(MdParser *parser);
> > +     CamHelper(MdParser *parser, unsigned int maxFrameLength,
> > +               unsigned int frameIntegrationDiff);
> >       virtual ~CamHelper();
> >       void SetCameraMode(const CameraMode &mode);
> >       MdParser &Parser() const { return *parser_; }
> >       uint32_t ExposureLines(double exposure_us) const;
> >       double Exposure(uint32_t exposure_lines) const; // in us
> > +     virtual uint32_t GetVBlanking(double &exposure_us, double
> minFrameDuration,
> > +                                   double maxFrameDuration) const;
> >       virtual uint32_t GainCode(double gain) const = 0;
> >       virtual double Gain(uint32_t gain_code) const = 0;
> >       virtual void GetDelays(int &exposure_delay, int &gain_delay) const;
> > @@ -76,10 +79,20 @@ public:
> >       virtual unsigned int HideFramesModeSwitch() const;
> >       virtual unsigned int MistrustFramesStartup() const;
> >       virtual unsigned int MistrustFramesModeSwitch() const;
> > +
> >  protected:
> >       MdParser *parser_;
> >       CameraMode mode_;
> > +
> > +private:
> >       bool initialized_;
> > +     /* Largest possible frame length, in units of lines. */
> > +     unsigned int maxFrameLength_;
> > +     /*
> > +      * Smallest difference between the frame length and integration
> time,
> > +      * in units of lines.
> > +      */
> > +     unsigned int frameIntegrationDiff_;
> >  };
> >
> >  // This is for registering camera helpers with the system, so that the
> > diff --git a/src/ipa/raspberrypi/cam_helper_imx219.cpp
> b/src/ipa/raspberrypi/cam_helper_imx219.cpp
> > index db8ab879..8688ec09 100644
> > --- a/src/ipa/raspberrypi/cam_helper_imx219.cpp
> > +++ b/src/ipa/raspberrypi/cam_helper_imx219.cpp
> > @@ -49,13 +49,22 @@ public:
> >       double Gain(uint32_t gain_code) const override;
> >       unsigned int MistrustFramesModeSwitch() const override;
> >       bool SensorEmbeddedDataPresent() const override;
> > +
> > +private:
> > +     /*
> > +      * Smallest difference between the frame length and integration
> time,
> > +      * in units of lines.
> > +      */
> > +     static constexpr int frameIntegrationDiff = 4;
> > +     /* Largest possible frame length, in units of lines. */
> > +     static constexpr int maxFrameLength = 0xffff;
> >  };
> >
> >  CamHelperImx219::CamHelperImx219()
> >  #if ENABLE_EMBEDDED_DATA
> > -     : CamHelper(new MdParserImx219())
> > +     : CamHelper(new MdParserImx219(), maxFrameLength,
> frameIntegrationDiff)
> >  #else
> > -     : CamHelper(new MdParserRPi())
> > +     : CamHelper(new MdParserRPi(), maxFrameLength,
> frameIntegrationDiff)
> >  #endif
> >  {
> >  }
> > diff --git a/src/ipa/raspberrypi/cam_helper_imx477.cpp
> b/src/ipa/raspberrypi/cam_helper_imx477.cpp
> > index 0e896ac7..53961310 100644
> > --- a/src/ipa/raspberrypi/cam_helper_imx477.cpp
> > +++ b/src/ipa/raspberrypi/cam_helper_imx477.cpp
> > @@ -38,10 +38,19 @@ public:
> >       uint32_t GainCode(double gain) const override;
> >       double Gain(uint32_t gain_code) const override;
> >       bool SensorEmbeddedDataPresent() const override;
> > +
> > +private:
> > +     /*
> > +      * Smallest difference between the frame length and integration
> time,
> > +      * in units of lines.
> > +      */
> > +     static constexpr int frameIntegrationDiff = 22;
> > +     /* Largest possible frame length, in units of lines. */
> > +     static constexpr int maxFrameLength = 0xffdc;
> >  };
> >
> >  CamHelperImx477::CamHelperImx477()
> > -     : CamHelper(new MdParserImx477())
> > +     : CamHelper(new MdParserImx477(), maxFrameLength,
> frameIntegrationDiff)
> >  {
> >  }
> >
> > diff --git a/src/ipa/raspberrypi/cam_helper_ov5647.cpp
> b/src/ipa/raspberrypi/cam_helper_ov5647.cpp
> > index 0b841cd1..2bd8a754 100644
> > --- a/src/ipa/raspberrypi/cam_helper_ov5647.cpp
> > +++ b/src/ipa/raspberrypi/cam_helper_ov5647.cpp
> > @@ -23,6 +23,15 @@ public:
> >       unsigned int HideFramesModeSwitch() const override;
> >       unsigned int MistrustFramesStartup() const override;
> >       unsigned int MistrustFramesModeSwitch() const override;
> > +
> > +private:
> > +     /*
> > +      * Smallest difference between the frame length and integration
> time,
> > +      * in units of lines.
> > +      */
> > +     static constexpr int frameIntegrationDiff = 4;
> > +     /* Largest possible frame length, in units of lines. */
> > +     static constexpr int maxFrameLength = 0xffff;
> >  };
> >
> >  /*
> > @@ -31,7 +40,7 @@ public:
> >   */
> >
> >  CamHelperOv5647::CamHelperOv5647()
> > -     : CamHelper(new MdParserRPi())
> > +     : CamHelper(new MdParserRPi(), maxFrameLength,
> frameIntegrationDiff)
> >  {
> >  }
> >
> > diff --git a/src/ipa/raspberrypi/raspberrypi.cpp
> b/src/ipa/raspberrypi/raspberrypi.cpp
> > index d087b07e..d309536b 100644
> > --- a/src/ipa/raspberrypi/raspberrypi.cpp
> > +++ b/src/ipa/raspberrypi/raspberrypi.cpp
> > @@ -58,6 +58,8 @@ namespace libcamera {
> >  /* Configure the sensor with these values initially. */
> >  constexpr double DefaultAnalogueGain = 1.0;
> >  constexpr unsigned int DefaultExposureTime = 20000;
> > +constexpr double defaultMinFrameDuration = 1e6 / 30.0;
> > +constexpr double defaultMaxFrameDuration = 1e6 / 0.01;
> >
> >  LOG_DEFINE_CATEGORY(IPARPI)
> >
> > @@ -150,6 +152,9 @@ private:
> >
> >       /* Distinguish the first camera start from others. */
> >       bool firstStart_;
> > +
> > +     /* Frame duration (1/fps) given in microseconds. */
> > +     double minFrameDuration_, maxFrameDuration_;
> >  };
> >
> >  int IPARPi::init(const IPASettings &settings)
> > @@ -332,7 +337,8 @@ void IPARPi::configure(const CameraSensorInfo
> &sensorInfo,
> >               sensorMetadata = helper_->SensorEmbeddedDataPresent();
> >
> >               result->data.push_back(gainDelay);
> > -             result->data.push_back(exposureDelay);
> > +             result->data.push_back(exposureDelay); /* For EXPOSURE
> ctrl */
> > +             result->data.push_back(exposureDelay); /* For VBLANK ctrl
> */
> >               result->data.push_back(sensorMetadata);
> >
> >               result->operation |= RPi::IPA_CONFIG_STAGGERED_WRITE;
> > @@ -377,6 +383,9 @@ void IPARPi::configure(const CameraSensorInfo
> &sensorInfo,
> >               controller_.Initialise();
> >               controllerInit_ = true;
> >
> > +             minFrameDuration_ = defaultMinFrameDuration;
> > +             maxFrameDuration_ = defaultMaxFrameDuration;
> > +
> >               /* Supply initial values for gain and exposure. */
> >               ControlList ctrls(sensorCtrls_);
> >               AgcStatus agcStatus;
> > @@ -524,7 +533,8 @@ bool IPARPi::validateSensorControls()
> >  {
> >       static const uint32_t ctrls[] = {
> >               V4L2_CID_ANALOGUE_GAIN,
> > -             V4L2_CID_EXPOSURE
> > +             V4L2_CID_EXPOSURE,
> > +             V4L2_CID_VBLANK
> >       };
> >
> >       for (auto c : ctrls) {
> > @@ -804,6 +814,24 @@ void IPARPi::queueRequest(const ControlList
> &controls)
> >                       break;
> >               }
> >
> > +             case controls::FRAME_DURATIONS: {
> > +                     auto frameDurations = ctrl.second.get<Span<const
> int64_t>>();
> > +
> > +                     /* This will be applied once AGC recalculations
> occur. */
> > +                     minFrameDuration_ = frameDurations[0] ?
> frameDurations[0] : defaultMinFrameDuration;
> > +                     maxFrameDuration_ = frameDurations[1] ?
> frameDurations[1] : defaultMaxFrameDuration;
>
> Should it be documented in patch 1/3 that setting the min or max to 0
> will reset the limit to the default ?
>

There was a mention of this in the control documentation at an earlier
revision.  Jacopo suggested we remove it for now, as it was a bit ambiguous
as to what a "default" frame duration is.  It could be a sensor provided
default, or as is the case with Raspberry Pi, an IPA provided default,
or...  I was a bit torn as to whether we needed a way to set defaults at
all.  What do you think?


>
> Will the code behave correctly if min > max ?
>

No, bad things will happen :)  I will guard against this by ensuring max >=
min.


>
> > +
> > +                     /*
> > +                      * \todo The values returned in the metadata below
> must be
> > +                      * correctly clipped by what the sensor mode
> supports and
> > +                      * what the AGC exposure mode or manual shutter
> speed limits
> > +                      */
> > +                     libcameraMetadata_.set(controls::FrameDurations,
> > +                                            {
> static_cast<int64_t>(minFrameDuration_),
> > +
> static_cast<int64_t>(maxFrameDuration_) });
> > +                     break;
> > +             }
> > +
> >               default:
> >                       LOG(IPARPI, Warning)
> >                               << "Ctrl " << controls::controls.at
> (ctrl.first)->name()
> > @@ -962,15 +990,27 @@ void IPARPi::applyAWB(const struct AwbStatus
> *awbStatus, ControlList &ctrls)
> >  void IPARPi::applyAGC(const struct AgcStatus *agcStatus, ControlList
> &ctrls)
> >  {
> >       int32_t gainCode = helper_->GainCode(agcStatus->analogue_gain);
> > -     int32_t exposureLines =
> helper_->ExposureLines(agcStatus->shutter_time);
> >
> > -     LOG(IPARPI, Debug) << "Applying AGC Exposure: " <<
> agcStatus->shutter_time
> > -                        << " (Shutter lines: " << exposureLines << ")
> Gain: "
> > +     /* GetVBlanking might clip exposure time to the fps limits. */
> > +     double exposure = agcStatus->shutter_time;
> > +     int32_t vblanking = helper_->GetVBlanking(exposure,
> minFrameDuration_,
> > +                                               maxFrameDuration_);
> > +     int32_t exposureLines = helper_->ExposureLines(exposure);
> > +
> > +     LOG(IPARPI, Debug) << "Applying AGC Exposure: " << exposure
> > +                        << " (Shutter lines: " << exposureLines << ",
> AGC requested "
> > +                        << agcStatus->shutter_time << ") Gain: "
> >                          << agcStatus->analogue_gain << " (Gain Code: "
> >                          << gainCode << ")";
> >
> > -     ctrls.set(V4L2_CID_ANALOGUE_GAIN, gainCode);
> > +     /*
> > +      * Due to the behavior of V4L2, the current value of VBLANK could
> clip the
> > +      * exposure time without us knowing. The next time though this
> function should
> > +      * clip exposure correctly.
> > +      */
>
> This is something we should address in V4L2 (obviously not a blocker for
> this series). If you could design it from scratch, what would be a good
> API to configure the h/v blanking (possibly expressed as h/v active
> instead of blanking) and exposure time ?
>

This is purely personal preference of course, but I would love it if the
world worked like this:

1) Userland sets a minimum and maximum frame rate (or frame duration) on a
sensor device driver.  This can happen at the start of day, or during
runtime.
2) Userland then provides an exposure time (in us or ns rather than in
lines) to the sensor device driver during normal AE operation.
3) Based on the frame rate/duration limits the sensor will
automatically adjust the V and H blanking to fulfil the exposure time if it
can.

For normal sensors, H/V blanking operations have very similar meaning, but
for more advanced modes (e.g. ultra long exposures or global shutter modes
of operation) they lose that meaning.  I feel trying to encode all of that
in a kernel API might be hard as it's a moving target.  This is why I think
that the blanking is probably left to the driver to deal with in a device
specific way.  With useland in control of setting framerate/duration
limits, I see no reason why it would have any need to set blanking limits,
but of course, I could be missing use cases that I have never had to deal
with!

Regards,
Naush



>
> > +     ctrls.set(V4L2_CID_VBLANK, vblanking);
> >       ctrls.set(V4L2_CID_EXPOSURE, exposureLines);
> > +     ctrls.set(V4L2_CID_ANALOGUE_GAIN, gainCode);
> >  }
> >
> >  void IPARPi::applyDG(const struct AgcStatus *dgStatus, ControlList
> &ctrls)
> > diff --git a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > index 7a5f5881..252cab64 100644
> > --- a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > +++ b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > @@ -1233,7 +1233,8 @@ int RPiCameraData::configureIPA(const
> CameraConfiguration *config)
> >               if (!staggeredCtrl_) {
> >                       staggeredCtrl_.init(unicam_[Unicam::Image].dev(),
> >                                           { { V4L2_CID_ANALOGUE_GAIN,
> result.data[resultIdx++] },
> > -                                           { V4L2_CID_EXPOSURE,
> result.data[resultIdx++] } });
> > +                                           { V4L2_CID_EXPOSURE,
> result.data[resultIdx++] },
> > +                                           { V4L2_CID_VBLANK,
> result.data[resultIdx++] } });
> >                       sensorMetadata_ = result.data[resultIdx++];
> >               }
> >       }
>
> --
> Regards,
>
> Laurent Pinchart
>

Hi Naush,

On Mon, Dec 21, 2020 at 11:26:58AM +0000, Naushir Patuck wrote:
> On Sun, 20 Dec 2020 at 05:52, Laurent Pinchart wrote:
> > On Fri, Dec 18, 2020 at 10:06:26AM +0000, Naushir Patuck wrote:
> > > Add support for setting V4L2_CID_VBLANK appropriately when setting
> > > V4L2_CID_EXPOSURE. This will allow adaptive framerates during
> > > viewfinder use cases (e.g. when the exposure time goes above 33ms, we
> > > can reduce the framerate to lower than 30fps).
> > >
> > > The minimum and maximum frame durations are provided via libcamera
> > > controls, and will prioritise exposure time limits over any AGC request.
> > >
> > > V4L2_CID_VBLANK is controlled through the staggered writer, just like
> > > the exposure and gain controls.
> > >
> > > Signed-off-by: Naushir Patuck <naush@raspberrypi.com>
> > > Reviewed-by: David Plowman <david.plowman@raspberrypi.com>
> > > Tested-by: David Plowman <david.plowman@raspberrypi.com>
> > > Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
> > > ---
> > >  include/libcamera/ipa/raspberrypi.h           |  1 +
> > >  src/ipa/raspberrypi/cam_helper.cpp            | 35 ++++++++++++-
> > >  src/ipa/raspberrypi/cam_helper.hpp            | 15 +++++-
> > >  src/ipa/raspberrypi/cam_helper_imx219.cpp     | 13 ++++-
> > >  src/ipa/raspberrypi/cam_helper_imx477.cpp     | 11 +++-
> > >  src/ipa/raspberrypi/cam_helper_ov5647.cpp     | 11 +++-
> > >  src/ipa/raspberrypi/raspberrypi.cpp           | 52 ++++++++++++++++---
> > >  .../pipeline/raspberrypi/raspberrypi.cpp      |  3 +-
> > >  8 files changed, 127 insertions(+), 14 deletions(-)
> > >
> > > diff --git a/include/libcamera/ipa/raspberrypi.h b/include/libcamera/ipa/raspberrypi.h
> > > index 01fe5abc..1de36039 100644
> > > --- a/include/libcamera/ipa/raspberrypi.h
> > > +++ b/include/libcamera/ipa/raspberrypi.h
> > > @@ -65,6 +65,7 @@ static const ControlInfoMap Controls = {
> > >       { &controls::Sharpness, ControlInfo(0.0f, 16.0f, 1.0f) },
> > >       { &controls::ColourCorrectionMatrix, ControlInfo(-16.0f, 16.0f) },
> > >       { &controls::ScalerCrop, ControlInfo(Rectangle{}, Rectangle(65535, 65535, 65535, 65535), Rectangle{}) },
> > > +     { &controls::FrameDurations, ControlInfo(1000, 1000000000) },
> > >  };
> > >
> > >  } /* namespace RPi */
> > > diff --git a/src/ipa/raspberrypi/cam_helper.cpp b/src/ipa/raspberrypi/cam_helper.cpp
> > > index 6efa0d7f..018c17b9 100644
> > > --- a/src/ipa/raspberrypi/cam_helper.cpp
> > > +++ b/src/ipa/raspberrypi/cam_helper.cpp
> > > @@ -34,8 +34,10 @@ CamHelper *CamHelper::Create(std::string const &cam_name)
> > >       return nullptr;
> > >  }
> > >
> > > -CamHelper::CamHelper(MdParser *parser)
> > > -     : parser_(parser), initialized_(false)
> > > +CamHelper::CamHelper(MdParser *parser, unsigned int maxFrameLength,
> > > +                  unsigned int frameIntegrationDiff)
> > > +     : parser_(parser), initialized_(false), maxFrameLength_(maxFrameLength),
> > > +       frameIntegrationDiff_(frameIntegrationDiff)
> > >  {
> > >  }
> > >
> > > @@ -56,6 +58,35 @@ double CamHelper::Exposure(uint32_t exposure_lines) const
> > >       return exposure_lines * mode_.line_length / 1000.0;
> > >  }
> > >
> > > +uint32_t CamHelper::GetVBlanking(double &exposure, double minFrameDuration,
> > > +                              double maxFrameDuration) const
> > > +{
> > > +     uint32_t frameLengthMin, frameLengthMax, vblank;
> > > +     uint32_t exposureLines = ExposureLines(exposure);
> > > +
> > > +     assert(initialized_);
> > > +
> > > +     /*
> > > +      * Clip frame length by the frame duration range and the maximum allowable
> > > +      * value in the sensor, given by maxFrameLength_.
> > > +      */
> > > +     frameLengthMin = std::clamp<uint32_t>(1e3 * minFrameDuration / mode_.line_length,
> > > +                                           mode_.height, maxFrameLength_);
> > > +     frameLengthMax = std::clamp<uint32_t>(1e3 * maxFrameDuration / mode_.line_length,
> > > +                                           mode_.height, maxFrameLength_);
> > > +     /*
> > > +      * Limit the exposure to the maximum frame duration requested, and
> > > +      * re-calculate if it has been clipped.
> > > +      */
> > > +     exposureLines = std::min(frameLengthMax - frameIntegrationDiff_, exposureLines);
> > > +     exposure = Exposure(exposureLines);
> > > +
> > > +     /* Limit the vblank to the range allowed by the frame length limits. */
> > > +     vblank = std::clamp(exposureLines + frameIntegrationDiff_,
> > > +                         frameLengthMin, frameLengthMax) - mode_.height;
> > > +     return vblank;
> > > +}
> > > +
> > >  void CamHelper::SetCameraMode(const CameraMode &mode)
> > >  {
> > >       mode_ = mode;
> > > diff --git a/src/ipa/raspberrypi/cam_helper.hpp b/src/ipa/raspberrypi/cam_helper.hpp
> > > index 044c2866..b1739a57 100644
> > > --- a/src/ipa/raspberrypi/cam_helper.hpp
> > > +++ b/src/ipa/raspberrypi/cam_helper.hpp
> > > @@ -62,12 +62,15 @@ class CamHelper
> > >  {
> > >  public:
> > >       static CamHelper *Create(std::string const &cam_name);
> > > -     CamHelper(MdParser *parser);
> > > +     CamHelper(MdParser *parser, unsigned int maxFrameLength,
> > > +               unsigned int frameIntegrationDiff);
> > >       virtual ~CamHelper();
> > >       void SetCameraMode(const CameraMode &mode);
> > >       MdParser &Parser() const { return *parser_; }
> > >       uint32_t ExposureLines(double exposure_us) const;
> > >       double Exposure(uint32_t exposure_lines) const; // in us
> > > +     virtual uint32_t GetVBlanking(double &exposure_us, double minFrameDuration,
> > > +                                   double maxFrameDuration) const;
> > >       virtual uint32_t GainCode(double gain) const = 0;
> > >       virtual double Gain(uint32_t gain_code) const = 0;
> > >       virtual void GetDelays(int &exposure_delay, int &gain_delay) const;
> > > @@ -76,10 +79,20 @@ public:
> > >       virtual unsigned int HideFramesModeSwitch() const;
> > >       virtual unsigned int MistrustFramesStartup() const;
> > >       virtual unsigned int MistrustFramesModeSwitch() const;
> > > +
> > >  protected:
> > >       MdParser *parser_;
> > >       CameraMode mode_;
> > > +
> > > +private:
> > >       bool initialized_;
> > > +     /* Largest possible frame length, in units of lines. */
> > > +     unsigned int maxFrameLength_;
> > > +     /*
> > > +      * Smallest difference between the frame length and integration time,
> > > +      * in units of lines.
> > > +      */
> > > +     unsigned int frameIntegrationDiff_;
> > >  };
> > >
> > >  // This is for registering camera helpers with the system, so that the
> > > diff --git a/src/ipa/raspberrypi/cam_helper_imx219.cpp b/src/ipa/raspberrypi/cam_helper_imx219.cpp
> > > index db8ab879..8688ec09 100644
> > > --- a/src/ipa/raspberrypi/cam_helper_imx219.cpp
> > > +++ b/src/ipa/raspberrypi/cam_helper_imx219.cpp
> > > @@ -49,13 +49,22 @@ public:
> > >       double Gain(uint32_t gain_code) const override;
> > >       unsigned int MistrustFramesModeSwitch() const override;
> > >       bool SensorEmbeddedDataPresent() const override;
> > > +
> > > +private:
> > > +     /*
> > > +      * Smallest difference between the frame length and integration time,
> > > +      * in units of lines.
> > > +      */
> > > +     static constexpr int frameIntegrationDiff = 4;
> > > +     /* Largest possible frame length, in units of lines. */
> > > +     static constexpr int maxFrameLength = 0xffff;
> > >  };
> > >
> > >  CamHelperImx219::CamHelperImx219()
> > >  #if ENABLE_EMBEDDED_DATA
> > > -     : CamHelper(new MdParserImx219())
> > > +     : CamHelper(new MdParserImx219(), maxFrameLength, frameIntegrationDiff)
> > >  #else
> > > -     : CamHelper(new MdParserRPi())
> > > +     : CamHelper(new MdParserRPi(), maxFrameLength, frameIntegrationDiff)
> > >  #endif
> > >  {
> > >  }
> > > diff --git a/src/ipa/raspberrypi/cam_helper_imx477.cpp b/src/ipa/raspberrypi/cam_helper_imx477.cpp
> > > index 0e896ac7..53961310 100644
> > > --- a/src/ipa/raspberrypi/cam_helper_imx477.cpp
> > > +++ b/src/ipa/raspberrypi/cam_helper_imx477.cpp
> > > @@ -38,10 +38,19 @@ public:
> > >       uint32_t GainCode(double gain) const override;
> > >       double Gain(uint32_t gain_code) const override;
> > >       bool SensorEmbeddedDataPresent() const override;
> > > +
> > > +private:
> > > +     /*
> > > +      * Smallest difference between the frame length and integration time,
> > > +      * in units of lines.
> > > +      */
> > > +     static constexpr int frameIntegrationDiff = 22;
> > > +     /* Largest possible frame length, in units of lines. */
> > > +     static constexpr int maxFrameLength = 0xffdc;
> > >  };
> > >
> > >  CamHelperImx477::CamHelperImx477()
> > > -     : CamHelper(new MdParserImx477())
> > > +     : CamHelper(new MdParserImx477(), maxFrameLength, frameIntegrationDiff)
> > >  {
> > >  }
> > >
> > > diff --git a/src/ipa/raspberrypi/cam_helper_ov5647.cpp b/src/ipa/raspberrypi/cam_helper_ov5647.cpp
> > > index 0b841cd1..2bd8a754 100644
> > > --- a/src/ipa/raspberrypi/cam_helper_ov5647.cpp
> > > +++ b/src/ipa/raspberrypi/cam_helper_ov5647.cpp
> > > @@ -23,6 +23,15 @@ public:
> > >       unsigned int HideFramesModeSwitch() const override;
> > >       unsigned int MistrustFramesStartup() const override;
> > >       unsigned int MistrustFramesModeSwitch() const override;
> > > +
> > > +private:
> > > +     /*
> > > +      * Smallest difference between the frame length and integration time,
> > > +      * in units of lines.
> > > +      */
> > > +     static constexpr int frameIntegrationDiff = 4;
> > > +     /* Largest possible frame length, in units of lines. */
> > > +     static constexpr int maxFrameLength = 0xffff;
> > >  };
> > >
> > >  /*
> > > @@ -31,7 +40,7 @@ public:
> > >   */
> > >
> > >  CamHelperOv5647::CamHelperOv5647()
> > > -     : CamHelper(new MdParserRPi())
> > > +     : CamHelper(new MdParserRPi(), maxFrameLength, frameIntegrationDiff)
> > >  {
> > >  }
> > >
> > > diff --git a/src/ipa/raspberrypi/raspberrypi.cpp b/src/ipa/raspberrypi/raspberrypi.cpp
> > > index d087b07e..d309536b 100644
> > > --- a/src/ipa/raspberrypi/raspberrypi.cpp
> > > +++ b/src/ipa/raspberrypi/raspberrypi.cpp
> > > @@ -58,6 +58,8 @@ namespace libcamera {
> > >  /* Configure the sensor with these values initially. */
> > >  constexpr double DefaultAnalogueGain = 1.0;
> > >  constexpr unsigned int DefaultExposureTime = 20000;
> > > +constexpr double defaultMinFrameDuration = 1e6 / 30.0;
> > > +constexpr double defaultMaxFrameDuration = 1e6 / 0.01;
> > >
> > >  LOG_DEFINE_CATEGORY(IPARPI)
> > >
> > > @@ -150,6 +152,9 @@ private:
> > >
> > >       /* Distinguish the first camera start from others. */
> > >       bool firstStart_;
> > > +
> > > +     /* Frame duration (1/fps) given in microseconds. */
> > > +     double minFrameDuration_, maxFrameDuration_;
> > >  };
> > >
> > >  int IPARPi::init(const IPASettings &settings)
> > > @@ -332,7 +337,8 @@ void IPARPi::configure(const CameraSensorInfo &sensorInfo,
> > >               sensorMetadata = helper_->SensorEmbeddedDataPresent();
> > >
> > >               result->data.push_back(gainDelay);
> > > -             result->data.push_back(exposureDelay);
> > > +             result->data.push_back(exposureDelay); /* For EXPOSURE ctrl */
> > > +             result->data.push_back(exposureDelay); /* For VBLANK ctrl */
> > >               result->data.push_back(sensorMetadata);
> > >
> > >               result->operation |= RPi::IPA_CONFIG_STAGGERED_WRITE;
> > > @@ -377,6 +383,9 @@ void IPARPi::configure(const CameraSensorInfo &sensorInfo,
> > >               controller_.Initialise();
> > >               controllerInit_ = true;
> > >
> > > +             minFrameDuration_ = defaultMinFrameDuration;
> > > +             maxFrameDuration_ = defaultMaxFrameDuration;
> > > +
> > >               /* Supply initial values for gain and exposure. */
> > >               ControlList ctrls(sensorCtrls_);
> > >               AgcStatus agcStatus;
> > > @@ -524,7 +533,8 @@ bool IPARPi::validateSensorControls()
> > >  {
> > >       static const uint32_t ctrls[] = {
> > >               V4L2_CID_ANALOGUE_GAIN,
> > > -             V4L2_CID_EXPOSURE
> > > +             V4L2_CID_EXPOSURE,
> > > +             V4L2_CID_VBLANK
> > >       };
> > >
> > >       for (auto c : ctrls) {
> > > @@ -804,6 +814,24 @@ void IPARPi::queueRequest(const ControlList &controls)
> > >                       break;
> > >               }
> > >
> > > +             case controls::FRAME_DURATIONS: {
> > > +                     auto frameDurations = ctrl.second.get<Span<const int64_t>>();
> > > +
> > > +                     /* This will be applied once AGC recalculations occur. */
> > > +                     minFrameDuration_ = frameDurations[0] ? frameDurations[0] : defaultMinFrameDuration;
> > > +                     maxFrameDuration_ = frameDurations[1] ? frameDurations[1] : defaultMaxFrameDuration;
> >
> > Should it be documented in patch 1/3 that setting the min or max to 0
> > will reset the limit to the default ?
> 
> There was a mention of this in the control documentation at an earlier
> revision.  Jacopo suggested we remove it for now, as it was a bit ambiguous
> as to what a "default" frame duration is.  It could be a sensor provided
> default, or as is the case with Raspberry Pi, an IPA provided default,
> or...  I was a bit torn as to whether we needed a way to set defaults at
> all.  What do you think?

The concept of default control values is indeed not explicit in the
documentation (something else for my todo list :-)), but we have
defaults already, they are used when applications don't set values for
all controls in requests. My concern here is that we document how to
constraint the frame duration (which will be used, in many cases, to set
a fixed frame duration), but we don't tell how to go back to a variable
frame rate.

The same issue exists with the ExposureTime and AnalogueGain controls,
applications can go back to variable exposure time and gain but setting
the controls to 0, but this isn't documented. We need to fix this
globally.

Could you add a \todo comment in patch 1/3 to remind of the issue ? I
think it could be useful to also already include a sentence explaining
how to go back to unconstrained mode, but feel free to disagree.

> > Will the code behave correctly if min > max ?
> 
> No, bad things will happen :)  I will guard against this by ensuring max >=
> min.
> 
> > > +
> > > +                     /*
> > > +                      * \todo The values returned in the metadata below must be
> > > +                      * correctly clipped by what the sensor mode supports and
> > > +                      * what the AGC exposure mode or manual shutter speed limits
> > > +                      */
> > > +                     libcameraMetadata_.set(controls::FrameDurations,
> > > +                                            { static_cast<int64_t>(minFrameDuration_),
> > > + static_cast<int64_t>(maxFrameDuration_) });
> > > +                     break;
> > > +             }
> > > +
> > >               default:
> > >                       LOG(IPARPI, Warning)
> > >                               << "Ctrl " << controls::controls.at (ctrl.first)->name()
> > > @@ -962,15 +990,27 @@ void IPARPi::applyAWB(const struct AwbStatus *awbStatus, ControlList &ctrls)
> > >  void IPARPi::applyAGC(const struct AgcStatus *agcStatus, ControlList &ctrls)
> > >  {
> > >       int32_t gainCode = helper_->GainCode(agcStatus->analogue_gain);
> > > -     int32_t exposureLines = helper_->ExposureLines(agcStatus->shutter_time);
> > >
> > > -     LOG(IPARPI, Debug) << "Applying AGC Exposure: " << agcStatus->shutter_time
> > > -                        << " (Shutter lines: " << exposureLines << ") Gain: "
> > > +     /* GetVBlanking might clip exposure time to the fps limits. */
> > > +     double exposure = agcStatus->shutter_time;
> > > +     int32_t vblanking = helper_->GetVBlanking(exposure, minFrameDuration_,
> > > +                                               maxFrameDuration_);
> > > +     int32_t exposureLines = helper_->ExposureLines(exposure);
> > > +
> > > +     LOG(IPARPI, Debug) << "Applying AGC Exposure: " << exposure
> > > +                        << " (Shutter lines: " << exposureLines << ", AGC requested "
> > > +                        << agcStatus->shutter_time << ") Gain: "
> > >                          << agcStatus->analogue_gain << " (Gain Code: "
> > >                          << gainCode << ")";
> > >
> > > -     ctrls.set(V4L2_CID_ANALOGUE_GAIN, gainCode);
> > > +     /*
> > > +      * Due to the behavior of V4L2, the current value of VBLANK could clip the
> > > +      * exposure time without us knowing. The next time though this function should
> > > +      * clip exposure correctly.
> > > +      */
> >
> > This is something we should address in V4L2 (obviously not a blocker for
> > this series). If you could design it from scratch, what would be a good
> > API to configure the h/v blanking (possibly expressed as h/v active
> > instead of blanking) and exposure time ?
> 
> This is purely personal preference of course, but I would love it if the
> world worked like this:
> 
> 1) Userland sets a minimum and maximum frame rate (or frame duration) on a
> sensor device driver.  This can happen at the start of day, or during
> runtime.
> 2) Userland then provides an exposure time (in us or ns rather than in
> lines) to the sensor device driver during normal AE operation.
> 3) Based on the frame rate/duration limits the sensor will
> automatically adjust the V and H blanking to fulfil the exposure time if it
> can.
> 
> For normal sensors, H/V blanking operations have very similar meaning, but
> for more advanced modes (e.g. ultra long exposures or global shutter modes
> of operation) they lose that meaning.  I feel trying to encode all of that
> in a kernel API might be hard as it's a moving target.  This is why I think
> that the blanking is probably left to the driver to deal with in a device
> specific way.  With useland in control of setting framerate/duration
> limits, I see no reason why it would have any need to set blanking limits,
> but of course, I could be missing use cases that I have never had to deal
> with!

It's interesting that you would like to see this moved to the kernel
side, I didn't expect that. There are multiple reasons we tried to push
this to userspace instead, the two main ones being that horizontal and
vertical blanking may have different implications (as you mentioned
above, it's not always the case but can be), and the other one being
that leaving blanking calculation to driver will mean different
behaviours in different drivers, which would get messy for userspace
pretty quickly.

One (smallà change I was considering recently was a replacement of the
blanking controls with H/V total controls. Sensors usually have hardware
limits on the horizontal and vertical total sizes, not on the blanking
itself (but it may not be the case for all hardware...).

> > > +     ctrls.set(V4L2_CID_VBLANK, vblanking);
> > >       ctrls.set(V4L2_CID_EXPOSURE, exposureLines);
> > > +     ctrls.set(V4L2_CID_ANALOGUE_GAIN, gainCode);
> > >  }
> > >
> > >  void IPARPi::applyDG(const struct AgcStatus *dgStatus, ControlList &ctrls)
> > > diff --git a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > > index 7a5f5881..252cab64 100644
> > > --- a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > > +++ b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > > @@ -1233,7 +1233,8 @@ int RPiCameraData::configureIPA(const CameraConfiguration *config)
> > >               if (!staggeredCtrl_) {
> > >                       staggeredCtrl_.init(unicam_[Unicam::Image].dev(),
> > >                                           { { V4L2_CID_ANALOGUE_GAIN, result.data[resultIdx++] },
> > > -                                           { V4L2_CID_EXPOSURE, result.data[resultIdx++] } });
> > > +                                           { V4L2_CID_EXPOSURE, result.data[resultIdx++] },
> > > +                                           { V4L2_CID_VBLANK, result.data[resultIdx++] } });
> > >                       sensorMetadata_ = result.data[resultIdx++];
> > >               }
> > >       }