[libcamera-devel] [PATCH v2 10/13] ipa: ipu3: agc: Introduce previous exposure value

[Jean-Michel Hautbois]

We need to calculate the gain on the previous exposure value calculated.
Now that we initialise the exposure and gain values in configure(), we
know the initial exposure value, and we can set it before any loop is
running.

Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois at ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
---
 src/ipa/ipu3/algorithms/agc.cpp | 13 +++++++++++--
 src/ipa/ipu3/algorithms/agc.h   |  1 +
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/src/ipa/ipu3/algorithms/agc.cpp b/src/ipa/ipu3/algorithms/agc.cpp
index eec77378..19f3a420 100644
--- a/src/ipa/ipu3/algorithms/agc.cpp
+++ b/src/ipa/ipu3/algorithms/agc.cpp
@@ -42,7 +42,8 @@ static constexpr double kEvGainTarget = 0.5;
 Agc::Agc()
 	: frameCount_(0), lastFrame_(0), iqMean_(0.0), lineDuration_(0s),
 	  minExposureLines_(0), maxExposureLines_(0), filteredExposure_(0s),
-	  filteredExposureNoDg_(0s), currentExposure_(0s), currentExposureNoDg_(0s)
+	  filteredExposureNoDg_(0s), currentExposure_(0s),
+	  currentExposureNoDg_(0s), prevExposureValue_(0s)
 {
 }
 
@@ -58,9 +59,14 @@ int Agc::configure(IPAContext &context, const IPAConfigInfo &configInfo)
 		context.configuration.agc.minAnalogueGain;
 	context.frameContext.agc.exposure = minExposureLines_;
 
+	/* \todo replace the exposure in lines storage with time based ones */
 	minExposureLines_ = context.configuration.agc.minShutterSpeed / lineDuration_;
 	maxExposureLines_ = context.configuration.agc.maxShutterSpeed / lineDuration_;
 
+	prevExposureValue_ = context.frameContext.agc.gain
+			   * context.frameContext.agc.exposure
+			   * lineDuration_;
+
 	return 0;
 }
 
@@ -146,7 +152,7 @@ void Agc::lockExposureGain(uint32_t &exposure, double &analogueGain)
 				    << " Gain " << analogueGain
 				    << " Needed ev gain " << evGain;
 
-		currentExposure_ = currentExposureNoDg_ * evGain;
+		currentExposure_ = prevExposureValue_ * evGain;
 		utils::Duration minShutterSpeed = minExposureLines_ * lineDuration_;
 		utils::Duration maxShutterSpeed = maxExposureLines_ * lineDuration_;
 
@@ -175,6 +181,9 @@ void Agc::lockExposureGain(uint32_t &exposure, double &analogueGain)
 
 		exposure = shutterTime / lineDuration_;
 		analogueGain = stepGain;
+
+		/* Update the exposure value for the next process call */
+		prevExposureValue_ = shutterTime * analogueGain;
 	}
 	lastFrame_ = frameCount_;
 }
diff --git a/src/ipa/ipu3/algorithms/agc.h b/src/ipa/ipu3/algorithms/agc.h
index cd26d08c..2ae88e9f 100644
--- a/src/ipa/ipu3/algorithms/agc.h
+++ b/src/ipa/ipu3/algorithms/agc.h
@@ -49,6 +49,7 @@ private:
 	utils::Duration filteredExposureNoDg_;
 	utils::Duration currentExposure_;
 	utils::Duration currentExposureNoDg_;
+	utils::Duration prevExposureValue_;
 
 	uint32_t stride_;
 };
-- 
2.32.0