ipa: libipa: Add AgcMeanLuminance base class

The Agc algorithms for the RkIsp1 and IPU3 IPAs do the same thing in
very large part; following the Rpi IPA's algorithm in spirit with a
few tunable values in that IPA being hardcoded in the libipa ones.
Add a new base class for AgcMeanLuminance which implements the same
algorithm and additionally parses yaml tuning files to inform an IPA
module's Agc algorithm about valid constraint and exposure modes and
their associated bounds.

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

1 files changed, 96 insertions, 0 deletions

diff --git a/src/ipa/libipa/agc_mean_luminance.h b/src/ipa/libipa/agc_mean_luminance.h
new file mode 100644
index 00000000..0a81c6d2
--- /dev/null
+++ b/src/ipa/libipa/agc_mean_luminance.h
@@ -0,0 +1,96 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2024 Ideas on Board Oy
+ *
+ agc_mean_luminance.h - Base class for mean luminance AGC algorithms
+ */
+
+#pragma once
+
+#include <map>
+#include <memory>
+#include <tuple>
+#include <vector>
+
+#include <libcamera/controls.h>
+
+#include "libcamera/internal/yaml_parser.h"
+
+#include "exposure_mode_helper.h"
+#include "histogram.h"
+
+namespace libcamera {
+
+namespace ipa {
+
+class AgcMeanLuminance
+{
+public:
+	AgcMeanLuminance();
+	virtual ~AgcMeanLuminance();
+
+	struct AgcConstraint {
+		enum class Bound {
+			lower = 0,
+			upper = 1
+		};
+		Bound bound;
+		double qLo;
+		double qHi;
+		double yTarget;
+	};
+
+	int parseTuningData(const YamlObject &tuningData);
+
+	void setLimits(utils::Duration minShutter, utils::Duration maxShutter,
+		       double minGain, double maxGain);
+
+	std::map<int32_t, std::vector<AgcConstraint>> constraintModes()
+	{
+		return constraintModes_;
+	}
+
+	std::map<int32_t, std::shared_ptr<ExposureModeHelper>> exposureModeHelpers()
+	{
+		return exposureModeHelpers_;
+	}
+
+	ControlInfoMap::Map controls()
+	{
+		return controls_;
+	}
+
+	std::tuple<utils::Duration, double, double>
+	calculateNewEv(uint32_t constraintModeIndex, uint32_t exposureModeIndex,
+		       const Histogram &yHist, utils::Duration effectiveExposureValue);
+
+	void resetFrameCount()
+	{
+		frameCount_ = 0;
+	}
+
+private:
+	virtual double estimateLuminance(const double gain) const = 0;
+
+	void parseRelativeLuminanceTarget(const YamlObject &tuningData);
+	void parseConstraint(const YamlObject &modeDict, int32_t id);
+	int parseConstraintModes(const YamlObject &tuningData);
+	int parseExposureModes(const YamlObject &tuningData);
+	double estimateInitialGain() const;
+	double constraintClampGain(uint32_t constraintModeIndex,
+				   const Histogram &hist,
+				   double gain);
+	utils::Duration filterExposure(utils::Duration exposureValue);
+
+	uint64_t frameCount_;
+	utils::Duration filteredExposure_;
+	double relativeLuminanceTarget_;
+
+	std::map<int32_t, std::vector<AgcConstraint>> constraintModes_;
+	std::map<int32_t, std::shared_ptr<ExposureModeHelper>> exposureModeHelpers_;
+	ControlInfoMap::Map controls_;
+};
+
+} /* namespace ipa */
+
+} /* namespace libcamera */