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

[Jean-Michel Hautbois]

We need to calculate the gain on the previous exposure value calculated.
This value needs to be updated after each process call, initialised to
0s.

Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois at ideasonboard.com>
---
 src/ipa/ipu3/algorithms/agc.cpp | 8 ++++++--
 src/ipa/ipu3/algorithms/agc.h   | 1 +
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/ipa/ipu3/algorithms/agc.cpp b/src/ipa/ipu3/algorithms/agc.cpp
index bd28998a..7efe0907 100644
--- a/src/ipa/ipu3/algorithms/agc.cpp
+++ b/src/ipa/ipu3/algorithms/agc.cpp
@@ -46,7 +46,8 @@ 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)
 {
 }
 
@@ -145,7 +146,7 @@ void Agc::lockExposureGain(uint32_t &exposure, double &analogueGain)
 				    << " Gain " << analogueGain
 				    << " Needed ev gain " << evGain;
 
-		currentExposure_ = currentExposureNoDg_ * evGain;
+		currentExposure_ = prevExposureValue * evGain;
 		Duration maxTotalExposure = kMaxShutterSpeed * kMaxGain;
 		currentExposure_ = std::min(currentExposure_, maxTotalExposure);
 		LOG(IPU3Agc, Debug) << "Target total exposure " << currentExposure_
@@ -182,6 +183,9 @@ 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 7605ab39..32817c4f 100644
--- a/src/ipa/ipu3/algorithms/agc.h
+++ b/src/ipa/ipu3/algorithms/agc.h
@@ -51,6 +51,7 @@ private:
 	Duration filteredExposureNoDg_;
 	Duration currentExposure_;
 	Duration currentExposureNoDg_;
+	Duration prevExposureValue;
 
 	uint32_t stride_;
 };
-- 
2.30.2