[libcamera-devel] [PATCH 11/13] ipa: ipu3: agc: Remove condition on exposure correction

[Jean-Michel Hautbois]

When the exposure is estimated, we verify if it changed enough for
exposure and gain to be updated.

There is no need for that because we are now filtering the value with
the previous one correctly, so if the change is very small is won't
change the exposure and analogue gain.

Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois at ideasonboard.com>
---
 src/ipa/ipu3/algorithms/agc.cpp | 96 ++++++++++++++++-----------------
 1 file changed, 46 insertions(+), 50 deletions(-)

diff --git a/src/ipa/ipu3/algorithms/agc.cpp b/src/ipa/ipu3/algorithms/agc.cpp
index 7efe0907..b922bcdf 100644
--- a/src/ipa/ipu3/algorithms/agc.cpp
+++ b/src/ipa/ipu3/algorithms/agc.cpp
@@ -132,61 +132,57 @@ void Agc::lockExposureGain(uint32_t &exposure, double &analogueGain)
 	if ((frameCount_ < kInitialFrameMinAECount) || (frameCount_ - lastFrame_ < kFrameSkipCount))
 		return;
 
-	/* Are we correctly exposed ? */
-	if (std::abs(iqMean_ - kEvGainTarget * knumHistogramBins) <= 1) {
-		LOG(IPU3Agc, Debug) << "!!! Good exposure with iqMean = " << iqMean_;
-	} else {
-		double evGain = kEvGainTarget * knumHistogramBins / iqMean_;
-
-		/* extracted from Rpi::Agc::computeTargetExposure */
-		Duration currentShutter = exposure * lineDuration_;
-		currentExposureNoDg_ = currentShutter * analogueGain;
-		LOG(IPU3Agc, Debug) << "Actual total exposure " << currentExposureNoDg_
-				    << " Shutter speed " << currentShutter
-				    << " Gain " << analogueGain
-				    << " Needed ev gain " << evGain;
-
-		currentExposure_ = prevExposureValue * evGain;
-		Duration maxTotalExposure = kMaxShutterSpeed * kMaxGain;
-		currentExposure_ = std::min(currentExposure_, maxTotalExposure);
-		LOG(IPU3Agc, Debug) << "Target total exposure " << currentExposure_
-				    << " maximum is " << maxTotalExposure;
-
-		/* \todo: estimate if we need to desaturate */
-		filterExposure();
-
-		Duration exposureValue = filteredExposure_;
-		Duration shutterTime = kMinShutterSpeed;
-		double stepGain = kMinGain;
-
-		if (shutterTime * stepGain < exposureValue) {
-			Duration maxShutterMinGain = kMaxShutterSpeed * stepGain;
-			if (maxShutterMinGain >= exposureValue) {
-				LOG(IPU3Agc, Debug) << "Setting shutterTime to " << shutterTime;
-				shutterTime = exposureValue / stepGain;
-			} else {
-				shutterTime = kMaxShutterSpeed;
-			}
+	double evGain = kEvGainTarget * knumHistogramBins / iqMean_;
+
+	/* extracted from Rpi::Agc::computeTargetExposure */
+	Duration currentShutter = exposure * lineDuration_;
+	currentExposureNoDg_ = currentShutter * analogueGain;
+	LOG(IPU3Agc, Debug) << "Actual total exposure " << currentExposureNoDg_
+				<< " Shutter speed " << currentShutter
+				<< " Gain " << analogueGain
+				<< " Needed ev gain " << evGain;
+
+	currentExposure_ = prevExposureValue * evGain;
+	Duration maxTotalExposure = kMaxShutterSpeed * kMaxGain;
+	currentExposure_ = std::min(currentExposure_, maxTotalExposure);
+	LOG(IPU3Agc, Debug) << "Target total exposure " << currentExposure_
+				<< " maximum is " << maxTotalExposure;
+
+	/* \todo: estimate if we need to desaturate */
+	filterExposure();
+
+	Duration exposureValue = filteredExposure_;
+	Duration shutterTime = kMinShutterSpeed;
+	double stepGain = kMinGain;
+
+	if (shutterTime * stepGain < exposureValue) {
+		Duration maxShutterMinGain = kMaxShutterSpeed * stepGain;
+		if (maxShutterMinGain >= exposureValue) {
+			LOG(IPU3Agc, Debug) << "Setting shutterTime to " << shutterTime;
+			shutterTime = exposureValue / stepGain;
+		} else {
+			shutterTime = kMaxShutterSpeed;
+		}
 
-			Duration maxGainShutter = kMaxGain * shutterTime;
-			if (maxGainShutter >= exposureValue) {
-				stepGain = exposureValue / shutterTime;
-				LOG(IPU3Agc, Debug) << "Setting analogue gain to " << stepGain;
-			} else {
-				stepGain = kMaxGain;
-			}
+		Duration maxGainShutter = kMaxGain * shutterTime;
+		if (maxGainShutter >= exposureValue) {
+			stepGain = exposureValue / shutterTime;
+			LOG(IPU3Agc, Debug) << "Setting analogue gain to " << stepGain;
+		} else {
+			stepGain = kMaxGain;
 		}
+	}
 
-		LOG(IPU3Agc, Debug) << "Divided up shutter and gain are "
-				<< shutterTime << " and "
-				<< stepGain;
+	LOG(IPU3Agc, Debug) << "Divided up shutter and gain are "
+			<< shutterTime << " and "
+			<< stepGain;
 
-		exposure = shutterTime / lineDuration_;
-		analogueGain = stepGain;
+	exposure = shutterTime / lineDuration_;
+	analogueGain = stepGain;
+
+	/* Update the exposure value for the next process call */
+	prevExposureValue = shutterTime * analogueGain;
 
-		/* Update the exposure value for the next process call */
-		prevExposureValue = shutterTime * analogueGain;
-	}
 	lastFrame_ = frameCount_;
 }
 
-- 
2.30.2