[libcamera-devel] [PATCH v3 06/14] ipa: ipu3: agc: Refactor ev gain calculation and testing

[Jean-Michel Hautbois]

When we compute the new gain, we use the iqMean_ and estimate an
exposure value gain to apply. Return early when the gain is less than
1%.

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 | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/src/ipa/ipu3/algorithms/agc.cpp b/src/ipa/ipu3/algorithms/agc.cpp
index 862366ac..71a7f39a 100644
--- a/src/ipa/ipu3/algorithms/agc.cpp
+++ b/src/ipa/ipu3/algorithms/agc.cpp
@@ -188,14 +188,6 @@ void Agc::filterExposure()
  */
 void Agc::computeExposure(IPAFrameContext &frameContext)
 {
-
-	/* Are we correctly exposed ? */
-	if (std::abs(iqMean_ - kEvGainTarget * knumHistogramBins) <= 1) {
-		LOG(IPU3Agc, Debug) << "We are well exposed (iqMean = "
-				    << iqMean_ << ")";
-		return;
-	}
-
 	/* Get the effective exposure and gain applied on the sensor. */
 	uint32_t &exposure = frameContext.sensor.exposure;
 	double &analogueGain = frameContext.sensor.gain;
@@ -203,6 +195,12 @@ void Agc::computeExposure(IPAFrameContext &frameContext)
 	/* Estimate the gain needed to have the proportion wanted */
 	double evGain = kEvGainTarget * knumHistogramBins / iqMean_;
 
+	if (std::abs(evGain - 1.0) < 0.01) {
+		LOG(IPU3Agc, Debug) << "We are well exposed (iqMean = "
+				    << iqMean_ << ")";
+		return;
+	}
+
 	/* extracted from Rpi::Agc::computeTargetExposure */
 	/* Calculate the shutter time in seconds */
 	utils::Duration currentShutter = exposure * lineDuration_;
-- 
2.32.0