[v3,07/19] ipa: camera_sensor_helper: Introduce minFrameDuration()

25059 diff mbox series

After having introduced CameraSensorHelper::maxShutterTime() which
calculates the maximum shutter time which can be achieved given
a frame duration, this patch introduces the opposite operation, that
given a desired shutter time calculates what is the minimum frame
duration required to achieve it.

The intended users of this function are IPA modules that after having
calculated a new exposure time need to regulate the frame duration to
achieve it.

Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
---
 src/ipa/libipa/camera_sensor_helper.cpp | 33 +++++++++++++++++++++++++++++++++
 src/ipa/libipa/camera_sensor_helper.h   |  2 ++
 2 files changed, 35 insertions(+)

Quoting Jacopo Mondi (2025-11-14 23:17:02)
> After having introduced CameraSensorHelper::maxShutterTime() which
> calculates the maximum shutter time which can be achieved given
> a frame duration, this patch introduces the opposite operation, that
> given a desired shutter time calculates what is the minimum frame
> duration required to achieve it.
> 
> The intended users of this function are IPA modules that after having
> calculated a new exposure time need to regulate the frame duration to
> achieve it.
> 
> Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
> ---
>  src/ipa/libipa/camera_sensor_helper.cpp | 33 +++++++++++++++++++++++++++++++++
>  src/ipa/libipa/camera_sensor_helper.h   |  2 ++
>  2 files changed, 35 insertions(+)
> 
> diff --git a/src/ipa/libipa/camera_sensor_helper.cpp b/src/ipa/libipa/camera_sensor_helper.cpp
> index 3c3e24c1cdefa4bca059352482bb29654a37b42f..a38f1eb40446b98a0db4642f086742674a13854f 100644
> --- a/src/ipa/libipa/camera_sensor_helper.cpp
> +++ b/src/ipa/libipa/camera_sensor_helper.cpp
> @@ -184,6 +184,39 @@ utils::Duration CameraSensorHelper::maxShutterTime(utils::Duration maxFrameDurat
>         return maxFrameDuration - exposureMargin * lineDuration;
>  }
>  
> +/**
> + * \brief Compute the minimum frame duration required for a desired exposure
> + * \param[in] shutterTime The shutter time
> + * \param[in] lineDuration The current sensor line duration
> + *
> + * This function returns the minimum frame duration required to achieve the
> + * desired \a shutterTime. The frame duration is calculated by adding to
> + * \a shutterTime the difference between the frame length and the maximum
> + * achievable integration time.
> + *
> + * The intended users of this function are IPA modules that want to calculate
> + * the minium required frame duration give a newly calculated shutter time.

s/minium/minimum/

s/give/given/

Otherwise, looks good to me.

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

> + *
> + * \todo The line duration should be a property of the CameraSensorHelper class
> + * instead of being provided by the IPA.
> + *
> + * \return The minimum frame duration required to achieve the desired shutter
> + * time
> + */
> +utils::Duration CameraSensorHelper::minFrameDuration(utils::Duration shutterTime,
> +                                                    utils::Duration lineDuration) const
> +{
> +       /* Use a static to rate-limit the error message. */
> +       static uint32_t exposureMargin = exposureMargin_.has_value()
> +                                      ? exposureMargin_.value() : 0;
> +       if (!exposureMargin_.has_value() && !exposureMargin) {
> +               LOG(CameraSensorHelper, Warning)
> +                       << "Exposure margin not known. Default to 4";
> +               exposureMargin = 4;
> +       }
> +
> +       return shutterTime + exposureMargin * lineDuration;
> +}
>  /**
>   * \struct CameraSensorHelper::AnalogueGainLinear
>   * \brief Analogue gain constants for the linear gain model
> diff --git a/src/ipa/libipa/camera_sensor_helper.h b/src/ipa/libipa/camera_sensor_helper.h
> index a1cf4bc334ad3b9a51d26b345bd5f0630c7ae87c..e9b53f183e8e6d305b50b5f3b46dc0199efee018 100644
> --- a/src/ipa/libipa/camera_sensor_helper.h
> +++ b/src/ipa/libipa/camera_sensor_helper.h
> @@ -33,6 +33,8 @@ public:
>         double quantizeGain(double gain, double *quantizationGain) const;
>         utils::Duration maxShutterTime(utils::Duration maxFrameDuration,
>                                        utils::Duration lineDuration) const;
> +       utils::Duration minFrameDuration(utils::Duration exposureTime,
> +                                        utils::Duration lineDuration) const;
>  
>  protected:
>         struct AnalogueGainLinear {
> 
> -- 
> 2.51.1
>