[PATCH 10/10] ipa: rkisp1: Remove bespoke Agc functions

Daniel Scally dan.scally at ideasonboard.com
Fri Mar 22 14:14:51 CET 2024


Now that the rkisp1 Agc algorithm is a derivation of MeanLuminanceAgc
we can remove the bespoke functions from the IPA's class.

Signed-off-by: Daniel Scally <dan.scally at ideasonboard.com>
---
 src/ipa/rkisp1/algorithms/agc.cpp | 222 ------------------------------
 src/ipa/rkisp1/algorithms/agc.h   |   9 --
 2 files changed, 231 deletions(-)

diff --git a/src/ipa/rkisp1/algorithms/agc.cpp b/src/ipa/rkisp1/algorithms/agc.cpp
index 3389c471..5e6a8ba0 100644
--- a/src/ipa/rkisp1/algorithms/agc.cpp
+++ b/src/ipa/rkisp1/algorithms/agc.cpp
@@ -42,24 +42,7 @@ static constexpr double kMinAnalogueGain = 1.0;
 /* \todo Honour the FrameDurationLimits control instead of hardcoding a limit */
 static constexpr utils::Duration kMaxShutterSpeed = 60ms;
 
-/* Number of frames to wait before calculating stats on minimum exposure */
-static constexpr uint32_t kNumStartupFrames = 10;
-
-/* Target value to reach for the top 2% of the histogram */
-static constexpr double kEvGainTarget = 0.5;
-
-/*
- * Relative luminance target.
- *
- * It's a number that's chosen so that, when the camera points at a grey
- * target, the resulting image brightness is considered right.
- *
- * \todo Why is the value different between IPU3 and RkISP1 ?
- */
-static constexpr double kRelativeLuminanceTarget = 0.4;
-
 Agc::Agc()
-	: frameCount_(0), filteredExposure_(0s)
 {
 	supportsRaw_ = true;
 }
@@ -127,12 +110,6 @@ int Agc::configure(IPAContext &context, const IPACameraSensorInfo &configInfo)
 	context.configuration.agc.measureWindow.h_size = 3 * configInfo.outputSize.width / 4;
 	context.configuration.agc.measureWindow.v_size = 3 * configInfo.outputSize.height / 4;
 
-	/*
-	 * \todo Use the upcoming per-frame context API that will provide a
-	 * frame index
-	 */
-	frameCount_ = 0;
-
 	for (auto &[id, helper] : exposureModeHelpers()) {
 		/* \todo Run this again when FrameDurationLimits is passed in */
 		helper->configure(context.configuration.sensor.minShutterSpeed,
@@ -234,170 +211,6 @@ void Agc::prepare(IPAContext &context, const uint32_t frame,
 	params->module_en_update |= RKISP1_CIF_ISP_MODULE_HST;
 }
 
-/**
- * \brief Apply a filter on the exposure value to limit the speed of changes
- * \param[in] exposureValue The target exposure from the AGC algorithm
- *
- * The speed of the filter is adaptive, and will produce the target quicker
- * during startup, or when the target exposure is within 20% of the most recent
- * filter output.
- *
- * \return The filtered exposure
- */
-utils::Duration Agc::filterExposure(utils::Duration exposureValue)
-{
-	double speed = 0.2;
-
-	/* Adapt instantly if we are in startup phase. */
-	if (frameCount_ < kNumStartupFrames)
-		speed = 1.0;
-
-	/*
-	 * If we are close to the desired result, go faster to avoid making
-	 * multiple micro-adjustments.
-	 * \todo Make this customisable?
-	 */
-	if (filteredExposure_ < 1.2 * exposureValue &&
-	    filteredExposure_ > 0.8 * exposureValue)
-		speed = sqrt(speed);
-
-	filteredExposure_ = speed * exposureValue +
-			    filteredExposure_ * (1.0 - speed);
-
-	LOG(RkISP1Agc, Debug) << "After filtering, exposure " << filteredExposure_;
-
-	return filteredExposure_;
-}
-
-/**
- * \brief Estimate the new exposure and gain values
- * \param[inout] context The shared IPA Context
- * \param[in] frameContext The FrameContext for this frame
- * \param[in] yGain The gain calculated on the current brightness level
- * \param[in] iqMeanGain The gain calculated based on the relative luminance target
- */
-void Agc::computeExposure(IPAContext &context, IPAFrameContext &frameContext,
-			  double yGain, double iqMeanGain)
-{
-	IPASessionConfiguration &configuration = context.configuration;
-
-	/* Get the effective exposure and gain applied on the sensor. */
-	uint32_t exposure = frameContext.sensor.exposure;
-	double analogueGain = frameContext.sensor.gain;
-
-	/* Use the highest of the two gain estimates. */
-	double evGain = std::max(yGain, iqMeanGain);
-
-	utils::Duration minShutterSpeed = configuration.sensor.minShutterSpeed;
-	utils::Duration maxShutterSpeed = std::min(configuration.sensor.maxShutterSpeed,
-						   kMaxShutterSpeed);
-
-	double minAnalogueGain = std::max(configuration.sensor.minAnalogueGain,
-					  kMinAnalogueGain);
-	double maxAnalogueGain = configuration.sensor.maxAnalogueGain;
-
-	/* Consider within 1% of the target as correctly exposed. */
-	if (utils::abs_diff(evGain, 1.0) < 0.01)
-		return;
-
-	/* extracted from Rpi::Agc::computeTargetExposure. */
-
-	/* Calculate the shutter time in seconds. */
-	utils::Duration currentShutter = exposure * configuration.sensor.lineDuration;
-
-	/*
-	 * Update the exposure value for the next computation using the values
-	 * of exposure and gain really used by the sensor.
-	 */
-	utils::Duration effectiveExposureValue = currentShutter * analogueGain;
-
-	LOG(RkISP1Agc, Debug) << "Actual total exposure " << currentShutter * analogueGain
-			      << " Shutter speed " << currentShutter
-			      << " Gain " << analogueGain
-			      << " Needed ev gain " << evGain;
-
-	/*
-	 * Calculate the current exposure value for the scene as the latest
-	 * exposure value applied multiplied by the new estimated gain.
-	 */
-	utils::Duration exposureValue = effectiveExposureValue * evGain;
-
-	/* Clamp the exposure value to the min and max authorized. */
-	utils::Duration maxTotalExposure = maxShutterSpeed * maxAnalogueGain;
-	exposureValue = std::min(exposureValue, maxTotalExposure);
-	LOG(RkISP1Agc, Debug) << "Target total exposure " << exposureValue
-			      << ", maximum is " << maxTotalExposure;
-
-	/*
-	 * Divide the exposure value as new exposure and gain values.
-	 * \todo estimate if we need to desaturate
-	 */
-	exposureValue = filterExposure(exposureValue);
-
-	/*
-	 * Push the shutter time up to the maximum first, and only then
-	 * increase the gain.
-	 */
-	utils::Duration shutterTime = std::clamp<utils::Duration>(exposureValue / minAnalogueGain,
-								  minShutterSpeed, maxShutterSpeed);
-	double stepGain = std::clamp(exposureValue / shutterTime,
-				     minAnalogueGain, maxAnalogueGain);
-	LOG(RkISP1Agc, Debug) << "Divided up shutter and gain are "
-			      << shutterTime << " and "
-			      << stepGain;
-}
-
-/**
- * \brief Estimate the relative luminance of the frame with a given gain
- * \param[in] expMeans The mean luminance values, from the RkISP1 statistics
- * \param[in] gain The gain to apply to the frame
- *
- * This function estimates the average relative luminance of the frame that
- * would be output by the sensor if an additional \a gain was applied.
- *
- * The estimation is based on the AE statistics for the current frame. Y
- * averages for all cells are first multiplied by the gain, and then saturated
- * to approximate the sensor behaviour at high brightness values. The
- * approximation is quite rough, as it doesn't take into account non-linearities
- * when approaching saturation. In this case, saturating after the conversion to
- * YUV doesn't take into account the fact that the R, G and B components
- * contribute differently to the relative luminance.
- *
- * \todo Have a dedicated YUV algorithm ?
- *
- * The values are normalized to the [0.0, 1.0] range, where 1.0 corresponds to a
- * theoretical perfect reflector of 100% reference white.
- *
- * More detailed information can be found in:
- * https://en.wikipedia.org/wiki/Relative_luminance
- *
- * \return The relative luminance
- */
-double Agc::estimateLuminance(Span<const uint8_t> expMeans, double gain)
-{
-	double ySum = 0.0;
-
-	/* Sum the averages, saturated to 255. */
-	for (uint8_t expMean : expMeans)
-		ySum += std::min(expMean * gain, 255.0);
-
-	/* \todo Weight with the AWB gains */
-
-	return ySum / expMeans.size() / 255;
-}
-
-/**
- * \brief Estimate the mean value of the top 2% of the histogram
- * \param[in] hist The histogram statistics computed by the RkISP1
- * \return The mean value of the top 2% of the histogram
- */
-double Agc::measureBrightness(Span<const uint32_t> hist) const
-{
-	Histogram histogram{ hist };
-	/* Estimate the quantile mean of the top 2% of the histogram. */
-	return histogram.interQuantileMean(0.98, 1.0);
-}
-
 void Agc::fillMetadata(IPAContext &context, IPAFrameContext &frameContext,
 		       ControlList &metadata)
 {
@@ -465,43 +278,8 @@ void Agc::process(IPAContext &context, [[maybe_unused]] const uint32_t frame,
 	 * we receive), but is important in manual mode.
 	 */
 
-	const rkisp1_cif_isp_stat *params = &stats->params;
 	ASSERT(stats->meas_type & RKISP1_CIF_ISP_STAT_AUTOEXP);
 
-	Span<const uint8_t> ae{ params->ae.exp_mean, context.hw->numAeCells };
-	Span<const uint32_t> hist{
-		params->hist.hist_bins,
-		context.hw->numHistogramBins
-	};
-
-	double iqMean = measureBrightness(hist);
-	double iqMeanGain = kEvGainTarget * hist.size() / iqMean;
-
-	/*
-	 * Estimate the gain needed to achieve a relative luminance target. To
-	 * account for non-linearity caused by saturation, the value needs to be
-	 * estimated in an iterative process, as multiplying by a gain will not
-	 * increase the relative luminance by the same factor if some image
-	 * regions are saturated.
-	 */
-	double yGain = 1.0;
-	double yTarget = kRelativeLuminanceTarget;
-
-	for (unsigned int i = 0; i < 8; i++) {
-		double yValue = estimateLuminance(ae, yGain);
-		double extra_gain = std::min(10.0, yTarget / (yValue + .001));
-
-		yGain *= extra_gain;
-		LOG(RkISP1Agc, Debug) << "Y value: " << yValue
-				      << ", Y target: " << yTarget
-				      << ", gives gain " << yGain;
-		if (extra_gain < 1.01)
-			break;
-	}
-
-	computeExposure(context, frameContext, yGain, iqMeanGain);
-	frameCount_++;
-
 	parseStatistics(stats, context);
 
 	/*
diff --git a/src/ipa/rkisp1/algorithms/agc.h b/src/ipa/rkisp1/algorithms/agc.h
index 1271741e..311d4e94 100644
--- a/src/ipa/rkisp1/algorithms/agc.h
+++ b/src/ipa/rkisp1/algorithms/agc.h
@@ -44,21 +44,12 @@ public:
 		     ControlList &metadata) override;
 
 private:
-	void computeExposure(IPAContext &Context, IPAFrameContext &frameContext,
-			     double yGain, double iqMeanGain);
-	utils::Duration filterExposure(utils::Duration exposureValue);
-	double estimateLuminance(Span<const uint8_t> expMeans, double gain);
-	double measureBrightness(Span<const uint32_t> hist) const;
 	void fillMetadata(IPAContext &context, IPAFrameContext &frameContext,
 			  ControlList &metadata);
 	void parseStatistics(const rkisp1_stat_buffer *stats,
 			     IPAContext &context);
 	double estimateLuminance(double gain) override;
 
-	uint64_t frameCount_;
-
-	utils::Duration filteredExposure_;
-
 	Histogram hist_;
 	Span<const uint8_t> expMeans_;
 };
-- 
2.34.1



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