[libcamera-devel] [PATCH 3/5] src: ipa: raspberrypi: agc: Add GetDropFrames method to AGC base class

[David Plowman]

We add a GetDropFrames 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       | 11 +++++++++++
 src/ipa/raspberrypi/controller/rpi/agc.hpp       |  2 ++
 3 files changed, 14 insertions(+)

diff --git a/src/ipa/raspberrypi/controller/agc_algorithm.hpp b/src/ipa/raspberrypi/controller/agc_algorithm.hpp
index b4ea54fb..bfc9743f 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 GetDropFrames() 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..94c02d47 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);
+	drop_frames = params.get<unsigned int>("drop_frames", 6);
 	fast_reduce_threshold =
 		params.get<double>("fast_reduce_threshold", 0.4);
 	base_ev = params.get<double>("base_ev", 1.0);
@@ -206,6 +207,16 @@ void Agc::Resume()
 	fixed_analogue_gain_ = 0;
 }
 
+unsigned int Agc::GetDropFrames() const
+{
+	// If shutter and gain have been explicitly set, there is no
+	// convergence to happen, so no need to drop any frames.
+	if (fixed_shutter_ && fixed_analogue_gain_)
+		return 0;
+	else
+		return config_.drop_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..1de4d505 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 drop_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 GetDropFrames() const override;
 	void SetEv(double ev) override;
 	void SetFlickerPeriod(double flicker_period) override;
 	void SetFixedShutter(double fixed_shutter) override; // microseconds
-- 
2.20.1