ipa: raspberrypi: Pass the maximum allowable shutter speed into the AGC

In order to provide an optimal split between shutter speed and gain, the
AGC must know the maximum allowable shutter speed, as limited by the
maximum frame duration (either application provided or the default).

Add a new API function, SetMaxShutter, to the AgcAlgorithm class. The
IPA provides the maximum shutter speed for AGC calculations. This
applies to both the manual and auto AGC modes.

Signed-off-by: Naushir Patuck <naush@raspberrypi.com>
Reviewed-by: David Plowman <david.plowman@raspberrypi.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

1 files changed, 32 insertions, 15 deletions

diff --git a/src/ipa/raspberrypi/controller/rpi/agc.cpp b/src/ipa/raspberrypi/controller/rpi/agc.cpp
index eddd1684..f4cd5d26 100644
--- a/src/ipa/raspberrypi/controller/rpi/agc.cpp
+++ b/src/ipa/raspberrypi/controller/rpi/agc.cpp
@@ -157,7 +157,7 @@ Agc::Agc(Controller *controller)
 	  frame_count_(0), lock_count_(0),
 	  last_target_exposure_(0.0),
 	  ev_(1.0), flicker_period_(0.0),
-	  fixed_shutter_(0), fixed_analogue_gain_(0.0)
+	  max_shutter_(0), fixed_shutter_(0), fixed_analogue_gain_(0.0)
 {
 	memset(&awb_, 0, sizeof(awb_));
 	// Setting status_.total_exposure_value_ to zero initially tells us
@@ -227,11 +227,16 @@ void Agc::SetFlickerPeriod(double flicker_period)
 	flicker_period_ = flicker_period;
 }
 
+void Agc::SetMaxShutter(double max_shutter)
+{
+	max_shutter_ = max_shutter;
+}
+
 void Agc::SetFixedShutter(double fixed_shutter)
 {
 	fixed_shutter_ = fixed_shutter;
 	// Set this in case someone calls Pause() straight after.
-	status_.shutter_time = fixed_shutter;
+	status_.shutter_time = clipShutter(fixed_shutter_);
 }
 
 void Agc::SetFixedAnalogueGain(double fixed_analogue_gain)
@@ -261,7 +266,8 @@ void Agc::SwitchMode([[maybe_unused]] CameraMode const &camera_mode,
 {
 	housekeepConfig();
 
-	if (fixed_shutter_ != 0.0 && fixed_analogue_gain_ != 0.0) {
+	double fixed_shutter = clipShutter(fixed_shutter_);
+	if (fixed_shutter != 0.0 && fixed_analogue_gain_ != 0.0) {
 		// We're going to reset the algorithm here with these fixed values.
 
 		fetchAwbStatus(metadata);
@@ -269,14 +275,14 @@ void Agc::SwitchMode([[maybe_unused]] CameraMode const &camera_mode,
 		ASSERT(min_colour_gain != 0.0);
 
 		// This is the equivalent of computeTargetExposure and applyDigitalGain.
-		target_.total_exposure_no_dg = fixed_shutter_ * fixed_analogue_gain_;
+		target_.total_exposure_no_dg = fixed_shutter * fixed_analogue_gain_;
 		target_.total_exposure = target_.total_exposure_no_dg / min_colour_gain;
 
 		// Equivalent of filterExposure. This resets any "history".
 		filtered_ = target_;
 
 		// Equivalent of divideUpExposure.
-		filtered_.shutter = fixed_shutter_;
+		filtered_.shutter = fixed_shutter;
 		filtered_.analogue_gain = fixed_analogue_gain_;
 	} else if (status_.total_exposure_value) {
 		// On a mode switch, it's possible the exposure profile could change,
@@ -290,7 +296,7 @@ void Agc::SwitchMode([[maybe_unused]] CameraMode const &camera_mode,
 		// for any that weren't set.
 
 		// Equivalent of divideUpExposure.
-		filtered_.shutter = fixed_shutter_ ? fixed_shutter_ : config_.default_exposure_time;
+		filtered_.shutter = fixed_shutter ? fixed_shutter : config_.default_exposure_time;
 		filtered_.analogue_gain = fixed_analogue_gain_ ? fixed_analogue_gain_ : config_.default_analogue_gain;
 	}
 
@@ -403,7 +409,7 @@ void Agc::housekeepConfig()
 {
 	// First fetch all the up-to-date settings, so no one else has to do it.
 	status_.ev = ev_;
-	status_.fixed_shutter = fixed_shutter_;
+	status_.fixed_shutter = clipShutter(fixed_shutter_);
 	status_.fixed_analogue_gain = fixed_analogue_gain_;
 	status_.flicker_period = flicker_period_;
 	LOG(RPiAgc, Debug) << "ev " << status_.ev << " fixed_shutter "
@@ -582,13 +588,15 @@ void Agc::computeTargetExposure(double gain)
 		target_.total_exposure = current_.total_exposure_no_dg * gain;
 		// The final target exposure is also limited to what the exposure
 		// mode allows.
+		double max_shutter = status_.fixed_shutter != 0.0
+				   ? status_.fixed_shutter
+				   : exposure_mode_->shutter.back();
+		max_shutter = clipShutter(max_shutter);
 		double max_total_exposure =
-			(status_.fixed_shutter != 0.0
-			 ? status_.fixed_shutter
-			 : exposure_mode_->shutter.back()) *
+			max_shutter *
 			(status_.fixed_analogue_gain != 0.0
-			 ? status_.fixed_analogue_gain
-			 : exposure_mode_->gain.back());
+				 ? status_.fixed_analogue_gain
+				 : exposure_mode_->gain.back());
 		target_.total_exposure = std::min(target_.total_exposure,
 						  max_total_exposure);
 	}
@@ -671,6 +679,7 @@ void Agc::divideUpExposure()
 	shutter_time = status_.fixed_shutter != 0.0
 			       ? status_.fixed_shutter
 			       : exposure_mode_->shutter[0];
+	shutter_time = clipShutter(shutter_time);
 	analogue_gain = status_.fixed_analogue_gain != 0.0
 				? status_.fixed_analogue_gain
 				: exposure_mode_->gain[0];
@@ -678,14 +687,15 @@ void Agc::divideUpExposure()
 		for (unsigned int stage = 1;
 		     stage < exposure_mode_->gain.size(); stage++) {
 			if (status_.fixed_shutter == 0.0) {
-				if (exposure_mode_->shutter[stage] *
-					    analogue_gain >=
+				double stage_shutter =
+					clipShutter(exposure_mode_->shutter[stage]);
+				if (stage_shutter * analogue_gain >=
 				    exposure_value) {
 					shutter_time =
 						exposure_value / analogue_gain;
 					break;
 				}
-				shutter_time = exposure_mode_->shutter[stage];
+				shutter_time = stage_shutter;
 			}
 			if (status_.fixed_analogue_gain == 0.0) {
 				if (exposure_mode_->gain[stage] *
@@ -740,6 +750,13 @@ void Agc::writeAndFinish(Metadata *image_metadata, bool desaturate)
 			   << " analogue gain " << filtered_.analogue_gain;
 }
 
+double Agc::clipShutter(double shutter)
+{
+	if (max_shutter_)
+		shutter = std::min(shutter, max_shutter_);
+	return shutter;
+}
+
 // Register algorithm with the system.
 static Algorithm *Create(Controller *controller)
 {