[libcamera-devel] [PATCH v2 2/6] src: ipa: raspberrypi: agc: Add GetConvergenceFrames method to AGC base class

[David Plowman]

We add a GetConvergenceFrames method to the AgcAlgorithm class which
can be called when the AGC is started from scratch. It suggests how
many frames should be dropped before displaying any (while the AGC
converges).

The Raspberry Pi specific implementation makes this customisable from
the tuning file.

Signed-off-by: David Plowman <david.plowman at raspberrypi.com>
---
 src/ipa/raspberrypi/controller/agc_algorithm.hpp |  1 +
 src/ipa/raspberrypi/controller/rpi/agc.cpp       | 13 +++++++++++++
 src/ipa/raspberrypi/controller/rpi/agc.hpp       |  2 ++
 3 files changed, 16 insertions(+)

diff --git a/src/ipa/raspberrypi/controller/agc_algorithm.hpp b/src/ipa/raspberrypi/controller/agc_algorithm.hpp
index b4ea54fb..85fc6084 100644
--- a/src/ipa/raspberrypi/controller/agc_algorithm.hpp
+++ b/src/ipa/raspberrypi/controller/agc_algorithm.hpp
@@ -15,6 +15,7 @@ class AgcAlgorithm : public Algorithm
 public:
 	AgcAlgorithm(Controller *controller) : Algorithm(controller) {}
 	// An AGC algorithm must provide the following:
+	virtual unsigned int GetConvergenceFrames(unsigned int mistrust_frames) const = 0;
 	virtual void SetEv(double ev) = 0;
 	virtual void SetFlickerPeriod(double flicker_period) = 0;
 	virtual void SetFixedShutter(double fixed_shutter) = 0; // microseconds
diff --git a/src/ipa/raspberrypi/controller/rpi/agc.cpp b/src/ipa/raspberrypi/controller/rpi/agc.cpp
index 9da18c31..787918cc 100644
--- a/src/ipa/raspberrypi/controller/rpi/agc.cpp
+++ b/src/ipa/raspberrypi/controller/rpi/agc.cpp
@@ -142,6 +142,7 @@ void AgcConfig::Read(boost::property_tree::ptree const &params)
 	Y_target.Read(params.get_child("y_target"));
 	speed = params.get<double>("speed", 0.2);
 	startup_frames = params.get<uint16_t>("startup_frames", 10);
+	convergence_frames = params.get<unsigned int>("convergence_frames", 6);
 	fast_reduce_threshold =
 		params.get<double>("fast_reduce_threshold", 0.4);
 	base_ev = params.get<double>("base_ev", 1.0);
@@ -206,6 +207,18 @@ void Agc::Resume()
 	fixed_analogue_gain_ = 0;
 }
 
+unsigned int Agc::GetConvergenceFrames(unsigned int mistrust_frames) const
+{
+	// If shutter and gain have been explicitly set, there is no
+	// convergence to happen, so no need to drop any frames - return zero.
+	// Otherwise, any frames for which we have been told not to trust the
+	// statistics must be added to our own count.
+	if (fixed_shutter_ && fixed_analogue_gain_)
+		return 0;
+	else
+		return config_.convergence_frames + mistrust_frames;
+}
+
 void Agc::SetEv(double ev)
 {
 	ev_ = ev;
diff --git a/src/ipa/raspberrypi/controller/rpi/agc.hpp b/src/ipa/raspberrypi/controller/rpi/agc.hpp
index 95db1812..7d41608a 100644
--- a/src/ipa/raspberrypi/controller/rpi/agc.hpp
+++ b/src/ipa/raspberrypi/controller/rpi/agc.hpp
@@ -52,6 +52,7 @@ struct AgcConfig {
 	Pwl Y_target;
 	double speed;
 	uint16_t startup_frames;
+	unsigned int convergence_frames;
 	double max_change;
 	double min_change;
 	double fast_reduce_threshold;
@@ -74,6 +75,7 @@ public:
 	bool IsPaused() const override;
 	void Pause() override;
 	void Resume() override;
+	unsigned int GetConvergenceFrames(unsigned int mistrust_frames) const override;
 	void SetEv(double ev) override;
 	void SetFlickerPeriod(double flicker_period) override;
 	void SetFixedShutter(double fixed_shutter) override; // microseconds
-- 
2.20.1