ipa: rkisp1: Remove bespoke Agc functions

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

Reviewed-by: Stefan Klug <stefan.klug@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Signed-off-by: Daniel Scally <dan.scally@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

2 files changed, 14 insertions, 226 deletions

diff --git a/src/ipa/rkisp1/algorithms/agc.cpp b/src/ipa/rkisp1/algorithms/agc.cpp
index f8d1b9a3..3e98496b 100644
--- a/src/ipa/rkisp1/algorithms/agc.cpp
+++ b/src/ipa/rkisp1/algorithms/agc.cpp
@@ -36,30 +36,7 @@ namespace ipa::rkisp1::algorithms {
 
 LOG_DEFINE_CATEGORY(RkISP1Agc)
 
-/* Minimum limit for analogue gain value */
-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;
 }
@@ -116,12 +93,6 @@ 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;
-
 	/* \todo Run this again when FrameDurationLimits is passed in */
 	setLimits(context.configuration.sensor.minShutterSpeed,
 		  context.configuration.sensor.maxShutterSpeed,
@@ -223,122 +194,24 @@ 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)
+void Agc::fillMetadata(IPAContext &context, IPAFrameContext &frameContext,
+		       ControlList &metadata)
 {
-	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);
+	utils::Duration exposureTime = context.configuration.sensor.lineDuration
+				     * frameContext.sensor.exposure;
+	metadata.set(controls::AnalogueGain, frameContext.sensor.gain);
+	metadata.set(controls::ExposureTime, exposureTime.get<std::micro>());
 
-	/*
-	 * 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;
+	/* \todo Use VBlank value calculated from each frame exposure. */
+	uint32_t vTotal = context.configuration.sensor.size.height
+			+ context.configuration.sensor.defVBlank;
+	utils::Duration frameDuration = context.configuration.sensor.lineDuration
+				      * vTotal;
+	metadata.set(controls::FrameDuration, frameDuration.get<std::micro>());
 }
 
 /**
  * \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
@@ -352,8 +225,6 @@ void Agc::computeExposure(IPAContext &context, IPAFrameContext &frameContext,
  * 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.
  *
@@ -362,47 +233,6 @@ void Agc::computeExposure(IPAContext &context, IPAFrameContext &frameContext,
  *
  * \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)
-{
-	utils::Duration exposureTime = context.configuration.sensor.lineDuration
-				     * frameContext.sensor.exposure;
-	metadata.set(controls::AnalogueGain, frameContext.sensor.gain);
-	metadata.set(controls::ExposureTime, exposureTime.get<std::micro>());
-
-	/* \todo Use VBlank value calculated from each frame exposure. */
-	uint32_t vTotal = context.configuration.sensor.size.height
-			+ context.configuration.sensor.defVBlank;
-	utils::Duration frameDuration = context.configuration.sensor.lineDuration
-				      * vTotal;
-	metadata.set(controls::FrameDuration, frameDuration.get<std::micro>());
-}
-
 double Agc::estimateLuminance(double gain) const
 {
 	double ySum = 0.0;
@@ -447,40 +277,7 @@ void Agc::process(IPAContext &context, [[maybe_unused]] const uint32_t frame,
 	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_++;
-
+	Histogram hist({ params->hist.hist_bins, context.hw->numHistogramBins });
 	expMeans_ = { params->ae.exp_mean, context.hw->numAeCells };
 
 	/*
@@ -497,7 +294,7 @@ void Agc::process(IPAContext &context, [[maybe_unused]] const uint32_t frame,
 	std::tie(shutterTime, aGain, dGain) =
 		calculateNewEv(context.activeState.agc.constraintMode,
 			       context.activeState.agc.exposureMode,
-			       Histogram(hist), effectiveExposureValue);
+			       hist, effectiveExposureValue);
 
 	LOG(RkISP1Agc, Debug)
 		<< "Divided up shutter, analogue gain and digital gain are "
diff --git a/src/ipa/rkisp1/algorithms/agc.h b/src/ipa/rkisp1/algorithms/agc.h
index 34504459..f2f5b59d 100644
--- a/src/ipa/rkisp1/algorithms/agc.h
+++ b/src/ipa/rkisp1/algorithms/agc.h
@@ -44,19 +44,10 @@ 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);
 	double estimateLuminance(double gain) const override;
 
-	uint64_t frameCount_;
-
-	utils::Duration filteredExposure_;
-
 	Span<const uint8_t> expMeans_;
 };