[PATCH v7 18/18] libcamera: software_isp: Update black level only on exposure changes

[Milan Zamazal]

The black level is likely to get updated, if ever, only after exposure
or gain changes.  Don't compute its possible updates if exposure and
gain are unchanged.

It's probably not worth trying to implement something more
sophisticated.  Better to spend the effort on supporting tuning files.

Signed-off-by: Milan Zamazal <mzamazal at redhat.com>
Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
---
 src/ipa/simple/algorithms/blc.cpp | 9 ++++++++-
 src/ipa/simple/algorithms/blc.h   | 4 ++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/src/ipa/simple/algorithms/blc.cpp b/src/ipa/simple/algorithms/blc.cpp
index 755108b0..b9f2aaa6 100644
--- a/src/ipa/simple/algorithms/blc.cpp
+++ b/src/ipa/simple/algorithms/blc.cpp
@@ -30,10 +30,15 @@ int BlackLevel::configure(IPAContext &context,
 
 void BlackLevel::process(IPAContext &context,
 			 [[maybe_unused]] const uint32_t frame,
-			 [[maybe_unused]] IPAFrameContext &frameContext,
+			 IPAFrameContext &frameContext,
 			 const SwIspStats *stats,
 			 [[maybe_unused]] ControlList &metadata)
 {
+	if (frameContext.sensor.exposure == exposure_ &&
+	    frameContext.sensor.gain == gain_) {
+		return;
+	}
+
 	const SwIspStats::Histogram &histogram = stats->yHistogram;
 
 	/*
@@ -54,6 +59,8 @@ void BlackLevel::process(IPAContext &context,
 		seen += histogram[i];
 		if (seen >= pixelThreshold) {
 			context.activeState.blc.level = i * histogramRatio;
+			exposure_ = frameContext.sensor.exposure;
+			gain_ = frameContext.sensor.gain;
 			LOG(IPASoftBL, Debug)
 				<< "Auto-set black level: "
 				<< i << "/" << SwIspStats::kYHistogramSize
diff --git a/src/ipa/simple/algorithms/blc.h b/src/ipa/simple/algorithms/blc.h
index 49bdcc61..828ad8b1 100644
--- a/src/ipa/simple/algorithms/blc.h
+++ b/src/ipa/simple/algorithms/blc.h
@@ -24,6 +24,10 @@ public:
 		     IPAFrameContext &frameContext,
 		     const SwIspStats *stats,
 		     ControlList &metadata) override;
+
+private:
+	uint32_t exposure_;
+	double gain_;
 };
 
 } /* namespace ipa::soft::algorithms */
-- 
2.44.1