[libcamera-devel] [PATCH v3 14/14] ipa: ipu3: Use sensor limits for analogue gain

[Kieran Bingham]

Quoting Jean-Michel Hautbois (2021-10-21 17:44:01)
> Instead of using constants for the analogue gains limits, use the
> minimum and maximum from the configured sensor.
> 
> Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois at ideasonboard.com>
> Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>


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

> ---
>  src/ipa/ipu3/algorithms/agc.cpp | 19 ++++++++++---------
>  src/ipa/ipu3/algorithms/agc.h   |  3 +++
>  2 files changed, 13 insertions(+), 9 deletions(-)
> 
> diff --git a/src/ipa/ipu3/algorithms/agc.cpp b/src/ipa/ipu3/algorithms/agc.cpp
> index be59d0b0..2981abc7 100644
> --- a/src/ipa/ipu3/algorithms/agc.cpp
> +++ b/src/ipa/ipu3/algorithms/agc.cpp
> @@ -30,10 +30,9 @@ static constexpr uint32_t kInitialFrameMinAECount = 4;
>  /* Number of frames to wait between new gain/exposure estimations */
>  static constexpr uint32_t kFrameSkipCount = 6;
>  
> -/* Maximum analogue gain value
> - * \todo grab it from a camera helper */
> -static constexpr double kMinGain = 1.0;
> -static constexpr double kMaxGain = 8.0;
> +/* Limits for analogue gain values */
> +static constexpr double kMinAnalogueGain = 1.0;
> +static constexpr double kMaxAnalogueGain = 8.0;
>  
>  /* Histogram constants */
>  static constexpr uint32_t knumHistogramBins = 256;
> @@ -57,9 +56,11 @@ int Agc::configure(IPAContext &context, const IPAConfigInfo &configInfo)
>         minExposureLines_ = context.configuration.agc.minShutterSpeed / lineDuration_;
>         maxExposureLines_ = context.configuration.agc.maxShutterSpeed / lineDuration_;
>  
> +       minAnalogueGain_ = std::max(context.configuration.agc.minAnalogueGain, kMinAnalogueGain);
> +       maxAnalogueGain_ = std::min(context.configuration.agc.maxAnalogueGain, kMaxAnalogueGain);
> +
>         /* Configure the default exposure and gain. */
> -       context.frameContext.agc.gain =
> -               context.configuration.agc.minAnalogueGain;
> +       context.frameContext.agc.gain = minAnalogueGain_;
>         context.frameContext.agc.exposure = minExposureLines_;
>  
>         prevExposureValue_ = context.frameContext.agc.gain
> @@ -142,7 +143,7 @@ void Agc::lockExposureGain(uint32_t &exposure, double &analogueGain)
>         utils::Duration minShutterSpeed = minExposureLines_ * lineDuration_;
>         utils::Duration maxShutterSpeed = maxExposureLines_ * lineDuration_;
>  
> -       utils::Duration maxTotalExposure = maxShutterSpeed * kMaxGain;
> +       utils::Duration maxTotalExposure = maxShutterSpeed * maxAnalogueGain_;
>         currentExposure_ = std::min(currentExposure_, maxTotalExposure);
>         LOG(IPU3Agc, Debug) << "Target total exposure " << currentExposure_
>                             << ", maximum is " << maxTotalExposure;
> @@ -157,10 +158,10 @@ void Agc::lockExposureGain(uint32_t &exposure, double &analogueGain)
>         * Push the shutter time up to the maximum first, and only then
>         * increase the gain.
>         */
> -       shutterTime = std::clamp<utils::Duration>(exposureValue / kMinGain,
> +       shutterTime = std::clamp<utils::Duration>(exposureValue / minAnalogueGain_,
>                                                   minShutterSpeed, maxShutterSpeed);
>         double stepGain = std::clamp(exposureValue / shutterTime,
> -                                    kMinGain, kMaxGain);
> +                                    minAnalogueGain_, maxAnalogueGain_);
>         LOG(IPU3Agc, Debug) << "Divided up shutter and gain are "
>                             << shutterTime << " and "
>                             << stepGain;
> diff --git a/src/ipa/ipu3/algorithms/agc.h b/src/ipa/ipu3/algorithms/agc.h
> index ad133b98..1840205b 100644
> --- a/src/ipa/ipu3/algorithms/agc.h
> +++ b/src/ipa/ipu3/algorithms/agc.h
> @@ -45,6 +45,9 @@ private:
>         uint32_t minExposureLines_;
>         uint32_t maxExposureLines_;
>  
> +       double minAnalogueGain_;
> +       double maxAnalogueGain_;
> +
>         utils::Duration filteredExposure_;
>         utils::Duration currentExposure_;
>         utils::Duration prevExposureValue_;
> -- 
> 2.32.0
>