[libcamera-devel] [PATCH 1/4] ipa: ipu3: Return filtered value

[Jean-Michel Hautbois]

When the current exposure value is calculated, it is cached and used by
filterExposure(). Use private filteredExposure_ and pass currentExposure
as a member variable.

In order to limit the use of filteredExposure_, return the value from
filterExposure().

While at it, remove a stale comment.

Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois at ideasonboard.com>
---
 src/ipa/ipu3/algorithms/agc.cpp | 31 ++++++++++++++++---------------
 src/ipa/ipu3/algorithms/agc.h   |  3 +--
 2 files changed, 17 insertions(+), 17 deletions(-)

diff --git a/src/ipa/ipu3/algorithms/agc.cpp b/src/ipa/ipu3/algorithms/agc.cpp
index 582f0ae1..2945a138 100644
--- a/src/ipa/ipu3/algorithms/agc.cpp
+++ b/src/ipa/ipu3/algorithms/agc.cpp
@@ -71,7 +71,7 @@ static constexpr double kRelativeLuminanceTarget = 0.16;
 
 Agc::Agc()
 	: frameCount_(0), lineDuration_(0s), minShutterSpeed_(0s),
-	  maxShutterSpeed_(0s), filteredExposure_(0s), currentExposure_(0s)
+	  maxShutterSpeed_(0s), filteredExposure_(0s)
 {
 }
 
@@ -143,7 +143,7 @@ double Agc::measureBrightness(const ipu3_uapi_stats_3a *stats,
 /**
  * \brief Apply a filter on the exposure value to limit the speed of changes
  */
-void Agc::filterExposure()
+utils::Duration Agc::filterExposure(utils::Duration currentExposure)
 {
 	double speed = 0.2;
 
@@ -152,23 +152,24 @@ void Agc::filterExposure()
 		speed = 1.0;
 
 	if (filteredExposure_ == 0s) {
-		/* DG stands for digital gain.*/
-		filteredExposure_ = currentExposure_;
+		filteredExposure_ = currentExposure;
 	} else {
 		/*
 		 * If we are close to the desired result, go faster to avoid making
 		 * multiple micro-adjustments.
 		 * \todo Make this customisable?
 		 */
-		if (filteredExposure_ < 1.2 * currentExposure_ &&
-		    filteredExposure_ > 0.8 * currentExposure_)
+		if (filteredExposure_ < 1.2 * currentExposure &&
+		    filteredExposure_ > 0.8 * currentExposure)
 			speed = sqrt(speed);
 
-		filteredExposure_ = speed * currentExposure_ +
+		filteredExposure_ = speed * currentExposure +
 				filteredExposure_ * (1.0 - speed);
 	}
 
 	LOG(IPU3Agc, Debug) << "After filtering, total_exposure " << filteredExposure_;
+
+	return filteredExposure_;
 }
 
 /**
@@ -212,19 +213,19 @@ void Agc::computeExposure(IPAFrameContext &frameContext, double yGain,
 	 * Calculate the current exposure value for the scene as the latest
 	 * exposure value applied multiplied by the new estimated gain.
 	 */
-	currentExposure_ = effectiveExposureValue * evGain;
+	utils::Duration currentExposure = effectiveExposureValue * evGain;
 
 	/* Clamp the exposure value to the min and max authorized */
 	utils::Duration maxTotalExposure = maxShutterSpeed_ * maxAnalogueGain_;
-	currentExposure_ = std::min(currentExposure_, maxTotalExposure);
-	LOG(IPU3Agc, Debug) << "Target total exposure " << currentExposure_
+	currentExposure = std::min(currentExposure, maxTotalExposure);
+	LOG(IPU3Agc, Debug) << "Target total exposure " << currentExposure
 			    << ", maximum is " << maxTotalExposure;
 
-	/* \todo: estimate if we need to desaturate */
-	filterExposure();
-
-	/* Divide the exposure value as new exposure and gain values */
-	utils::Duration exposureValue = filteredExposure_;
+	/*
+	 * Divide the exposure value as new exposure and gain values
+	 * \todo: estimate if we need to desaturate
+	 */
+	utils::Duration exposureValue = filterExposure(currentExposure);
 	utils::Duration shutterTime;
 
 	/*
diff --git a/src/ipa/ipu3/algorithms/agc.h b/src/ipa/ipu3/algorithms/agc.h
index 96ec7005..84bfe045 100644
--- a/src/ipa/ipu3/algorithms/agc.h
+++ b/src/ipa/ipu3/algorithms/agc.h
@@ -33,7 +33,7 @@ public:
 private:
 	double measureBrightness(const ipu3_uapi_stats_3a *stats,
 				 const ipu3_uapi_grid_config &grid) const;
-	void filterExposure();
+	utils::Duration filterExposure(utils::Duration currentExposure);
 	void computeExposure(IPAFrameContext &frameContext, double yGain,
 			     double iqMeanGain);
 	double estimateLuminance(IPAFrameContext &frameContext,
@@ -51,7 +51,6 @@ private:
 	double maxAnalogueGain_;
 
 	utils::Duration filteredExposure_;
-	utils::Duration currentExposure_;
 
 	uint32_t stride_;
 };
-- 
2.32.0