[libcamera-devel] [PATCH v4 09/14] ipa: ipu3: agc: Use exposure in time for storage

[Umang Jain]

Hi JM,

On 11/11/21 7:39 PM, Jean-Michel Hautbois wrote:
> The minimum and maximum exposure are stored in lines. Replace it by
> values in time to simplify the calculations.
>
> Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois at ideasonboard.com>
> Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>


Reviewed-by: Umang Jain <umang.jain at ideasonboard.com>

> ---
>   src/ipa/ipu3/algorithms/agc.cpp | 21 +++++++++------------
>   src/ipa/ipu3/algorithms/agc.h   |  4 ++--
>   2 files changed, 11 insertions(+), 14 deletions(-)
>
> diff --git a/src/ipa/ipu3/algorithms/agc.cpp b/src/ipa/ipu3/algorithms/agc.cpp
> index d736f21c..86b71886 100644
> --- a/src/ipa/ipu3/algorithms/agc.cpp
> +++ b/src/ipa/ipu3/algorithms/agc.cpp
> @@ -79,8 +79,8 @@ static constexpr uint32_t kMaxLuminance = 255;
>   static constexpr double kNormalizedLumaTarget = 0.16;
>   
>   Agc::Agc()
> -	: frameCount_(0), iqMean_(0.0), lineDuration_(0s), minExposureLines_(0),
> -	  maxExposureLines_(0), filteredExposure_(0s), currentExposure_(0s)
> +	: frameCount_(0), iqMean_(0.0), lineDuration_(0s), minShutterSpeed_(0s),
> +	  maxShutterSpeed_(0s), filteredExposure_(0s), currentExposure_(0s)
>   {
>   }
>   
> @@ -99,17 +99,16 @@ int Agc::configure(IPAContext &context, const IPAConfigInfo &configInfo)
>   	lineDuration_ = configInfo.sensorInfo.lineLength * 1.0s
>   		      / configInfo.sensorInfo.pixelRate;
>   
> -	/* \todo replace the exposure in lines storage with time based ones. */
> -	minExposureLines_ = context.configuration.agc.minShutterSpeed / lineDuration_;
> -	maxExposureLines_ = std::min(context.configuration.agc.maxShutterSpeed / lineDuration_,
> -				     kMaxShutterSpeed / lineDuration_);
> +	minShutterSpeed_ = context.configuration.agc.minShutterSpeed;
> +	maxShutterSpeed_ = std::min(context.configuration.agc.maxShutterSpeed,
> +				    kMaxShutterSpeed);
>   
>   	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 = minAnalogueGain_;
> -	context.frameContext.agc.exposure = minExposureLines_;
> +	context.frameContext.agc.exposure = minShutterSpeed_ / lineDuration_;
>   
>   	return 0;
>   }
> @@ -242,11 +241,9 @@ void Agc::computeExposure(IPAFrameContext &frameContext, double currentYGain)
>   	 * exposure value applied multiplied by the new estimated gain.
>   	 */
>   	currentExposure_ = effectiveExposureValue * evGain;
> -	utils::Duration minShutterSpeed = minExposureLines_ * lineDuration_;
> -	utils::Duration maxShutterSpeed = maxExposureLines_ * lineDuration_;
>   
>   	/* Clamp the exposure value to the min and max authorized */
> -	utils::Duration maxTotalExposure = maxShutterSpeed * maxAnalogueGain_;
> +	utils::Duration maxTotalExposure = maxShutterSpeed_ * maxAnalogueGain_;
>   	currentExposure_ = std::min(currentExposure_, maxTotalExposure);
>   	LOG(IPU3Agc, Debug) << "Target total exposure " << currentExposure_
>   			    << ", maximum is " << maxTotalExposure;
> @@ -256,14 +253,14 @@ void Agc::computeExposure(IPAFrameContext &frameContext, double currentYGain)
>   
>   	/* Divide the exposure value as new exposure and gain values */
>   	utils::Duration exposureValue = filteredExposure_;
> -	utils::Duration shutterTime = minShutterSpeed;
> +	utils::Duration shutterTime;
>   
>   	/*
>   	* Push the shutter time up to the maximum first, and only then
>   	* increase the gain.
>   	*/
>   	shutterTime = std::clamp<utils::Duration>(exposureValue / minAnalogueGain_,
> -						  minShutterSpeed, maxShutterSpeed);
> +						  minShutterSpeed_, maxShutterSpeed_);
>   	double stepGain = std::clamp(exposureValue / shutterTime,
>   				     minAnalogueGain_, maxAnalogueGain_);
>   	LOG(IPU3Agc, Debug) << "Divided up shutter and gain are "
> diff --git a/src/ipa/ipu3/algorithms/agc.h b/src/ipa/ipu3/algorithms/agc.h
> index 1d085b40..f14d56b7 100644
> --- a/src/ipa/ipu3/algorithms/agc.h
> +++ b/src/ipa/ipu3/algorithms/agc.h
> @@ -46,8 +46,8 @@ private:
>   	double iqMean_;
>   
>   	utils::Duration lineDuration_;
> -	uint32_t minExposureLines_;
> -	uint32_t maxExposureLines_;
> +	utils::Duration minShutterSpeed_;
> +	utils::Duration maxShutterSpeed_;
>   
>   	double minAnalogueGain_;
>   	double maxAnalogueGain_;