ipa: ipu3: Derive ipu3::algorithms::Agc from AgcMeanLuminance

In preparation for switching to a derivation of AgcMeanLuminance, add
a function to parse and store the statistics for easy retrieval in an
overriding estimateLuminance() function.

Now that we have a MeanLuminanceAgc class that centralises our AEGC
algorithm, derive the IPU3's Agc class from it and plumb in the
necessary framework to enable it to be used. For simplicity's sake
this commit switches the algorithm to use the derived class, but
does not remove the bespoke functions at this time.

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

1 files changed, 112 insertions, 7 deletions

diff --git a/src/ipa/ipu3/algorithms/agc.cpp b/src/ipa/ipu3/algorithms/agc.cpp
index 606a237a..b1ba27fe 100644
--- a/src/ipa/ipu3/algorithms/agc.cpp
+++ b/src/ipa/ipu3/algorithms/agc.cpp
@@ -71,12 +71,34 @@ static constexpr uint32_t kNumStartupFrames = 10;
 static constexpr double kRelativeLuminanceTarget = 0.16;
 
 Agc::Agc()
-	: frameCount_(0), minShutterSpeed_(0s),
-	  maxShutterSpeed_(0s), filteredExposure_(0s)
+	: minShutterSpeed_(0s), maxShutterSpeed_(0s)
 {
 }
 
 /**
+ * \brief Initialise the AGC algorithm from tuning files
+ * \param[in] context The shared IPA context
+ * \param[in] tuningData The YamlObject containing Agc tuning data
+ *
+ * This function calls the base class' tuningData parsers to discover which
+ * control values are supported.
+ *
+ * \return 0 on success or errors from the base class
+ */
+int Agc::init(IPAContext &context, const YamlObject &tuningData)
+{
+	int ret;
+
+	ret = parseTuningData(tuningData);
+	if (ret)
+		return ret;
+
+	context.ctrlMap.merge(controls());
+
+	return 0;
+}
+
+/**
  * \brief Configure the AGC given a configInfo
  * \param[in] context The shared IPA context
  * \param[in] configInfo The IPA configuration data
@@ -90,6 +112,7 @@ int Agc::configure(IPAContext &context,
 	IPAActiveState &activeState = context.activeState;
 
 	stride_ = configuration.grid.stride;
+	bdsGrid_ = configuration.grid.bdsGrid;
 
 	minShutterSpeed_ = configuration.agc.minShutterSpeed;
 	maxShutterSpeed_ = std::min(configuration.agc.maxShutterSpeed,
@@ -103,6 +126,15 @@ int Agc::configure(IPAContext &context,
 	activeState.agc.exposure = 10ms / configuration.sensor.lineDuration;
 
 	frameCount_ = 0;
+
+	context.activeState.agc.constraintMode = constraintModes().begin()->first;
+	context.activeState.agc.exposureMode = exposureModeHelpers().begin()->first;
+
+	/* \todo Run this again when FrameDurationLimits is passed in */
+	setLimits(minShutterSpeed_, maxShutterSpeed_, minAnalogueGain_,
+		  maxAnalogueGain_);
+	resetFrameCount();
+
 	return 0;
 }
 
@@ -142,6 +174,39 @@ double Agc::measureBrightness(const ipu3_uapi_stats_3a *stats,
 	return Histogram(Span<uint32_t>(hist)).interQuantileMean(0.98, 1.0);
 }
 
+Histogram Agc::parseStatistics(const ipu3_uapi_stats_3a *stats,
+			       const ipu3_uapi_grid_config &grid)
+{
+	uint32_t hist[knumHistogramBins] = { 0 };
+
+	rgbTriples_.clear();
+
+	for (unsigned int cellY = 0; cellY < grid.height; cellY++) {
+		for (unsigned int cellX = 0; cellX < grid.width; cellX++) {
+			uint32_t cellPosition = cellY * stride_ + cellX;
+
+			const ipu3_uapi_awb_set_item *cell =
+				reinterpret_cast<const ipu3_uapi_awb_set_item *>(
+					&stats->awb_raw_buffer.meta_data[cellPosition]);
+
+			rgbTriples_.push_back({
+				cell->R_avg,
+				(cell->Gr_avg + cell->Gb_avg) / 2,
+				cell->B_avg
+			});
+
+			/*
+			 * Store the average green value to estimate the
+			 * brightness. Even the overexposed pixels are
+			 * taken into account.
+			 */
+			hist[(cell->Gr_avg + cell->Gb_avg) / 2]++;
+		}
+	}
+
+	return Histogram(Span<uint32_t>(hist));
+}
+
 /**
  * \brief Apply a filter on the exposure value to limit the speed of changes
  * \param[in] exposureValue The target exposure from the AGC algorithm
@@ -247,11 +312,6 @@ void Agc::computeExposure(IPAContext &context, IPAFrameContext &frameContext,
 	LOG(IPU3Agc, Debug) << "Divided up shutter and gain are "
 			    << shutterTime << " and "
 			    << stepGain;
-
-	IPAActiveState &activeState = context.activeState;
-	/* Update the estimated exposure and gain. */
-	activeState.agc.exposure = shutterTime / configuration.sensor.lineDuration;
-	activeState.agc.gain = stepGain;
 }
 
 /**
@@ -314,6 +374,23 @@ double Agc::estimateLuminance(IPAActiveState &activeState,
 	return ySum / (grid.height * grid.width) / 255;
 }
 
+double Agc::estimateLuminance(double gain) const
+{
+	double redSum = 0, greenSum = 0, blueSum = 0;
+
+	for (unsigned int i = 0; i < rgbTriples_.size(); i++) {
+		redSum += std::min(std::get<0>(rgbTriples_[i]) * gain, 255.0);
+		greenSum += std::min(std::get<1>(rgbTriples_[i]) * gain, 255.0);
+		blueSum += std::min(std::get<2>(rgbTriples_[i]) * gain, 255.0);
+	}
+
+	double ySum = redSum * rGain_ * 0.299
+		    + greenSum * gGain_ * 0.587
+		    + blueSum * bGain_ * 0.114;
+
+	return ySum / (bdsGrid_.height * bdsGrid_.width) / 255;
+}
+
 /**
  * \brief Process IPU3 statistics, and run AGC operations
  * \param[in] context The shared IPA context
@@ -366,8 +443,36 @@ void Agc::process(IPAContext &context, [[maybe_unused]] const uint32_t frame,
 	computeExposure(context, frameContext, yGain, iqMeanGain);
 	frameCount_++;
 
+	Histogram hist = parseStatistics(stats, context.configuration.grid.bdsGrid);
+	rGain_ = context.activeState.awb.gains.red;
+	gGain_ = context.activeState.awb.gains.blue;
+	bGain_ = context.activeState.awb.gains.green;
+
+	/*
+	 * The Agc algorithm needs to know the effective exposure value that was
+	 * applied to the sensor when the statistics were collected.
+	 */
 	utils::Duration exposureTime = context.configuration.sensor.lineDuration
 				     * frameContext.sensor.exposure;
+	double analogueGain = frameContext.sensor.gain;
+	utils::Duration effectiveExposureValue = exposureTime * analogueGain;
+
+	utils::Duration shutterTime;
+	double aGain, dGain;
+	std::tie(shutterTime, aGain, dGain) =
+		calculateNewEv(context.activeState.agc.constraintMode,
+			       context.activeState.agc.exposureMode, hist,
+			       effectiveExposureValue);
+
+	LOG(IPU3Agc, Debug)
+		<< "Divided up shutter, analogue gain and digital gain are "
+		<< shutterTime << ", " << aGain << " and " << dGain;
+
+	IPAActiveState &activeState = context.activeState;
+	/* Update the estimated exposure and gain. */
+	activeState.agc.exposure = shutterTime / context.configuration.sensor.lineDuration;
+	activeState.agc.gain = aGain;
+
 	metadata.set(controls::AnalogueGain, frameContext.sensor.gain);
 	metadata.set(controls::ExposureTime, exposureTime.get<std::micro>());