[libcamera-devel] [PATCH v1 6/6] ipa: raspberrypi: agc: Fix digital gain calculation for manual mode

[Naushir Patuck]

The digital gain calculation uses a total exposure value computed with the
current AGC state. However, this is wrong in the case of manual shutter/gain
controls, as the total exposure value used must be the value computed when the
AGC sent the manual shutter/gain controls to the pipeline handler to action.

To fix this, the IPA now adds the historical AgcStatus structure to the metadata
(tagged with "agc.delayed_status"). This historical AgcStatus structure contains
the total exposure value calculated when the AGC sent the manual shutter/gain
controls to the pipeline handler.

Signed-off-by: Naushir Patuck <naush at raspberrypi.com>
---
 src/ipa/raspberrypi/controller/rpi/agc.cpp | 10 ++++++++--
 src/ipa/raspberrypi/raspberrypi.cpp        | 11 +++++++++++
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/src/ipa/raspberrypi/controller/rpi/agc.cpp b/src/ipa/raspberrypi/controller/rpi/agc.cpp
index bd54a639d637..b18bd7b5b19e 100644
--- a/src/ipa/raspberrypi/controller/rpi/agc.cpp
+++ b/src/ipa/raspberrypi/controller/rpi/agc.cpp
@@ -408,6 +408,12 @@ void Agc::switchMode(CameraMode const &cameraMode,
 
 void Agc::prepare(Metadata *imageMetadata)
 {
+	Duration totalExposureValue = status_.totalExposureValue;
+	AgcStatus delayedStatus;
+
+	if (!imageMetadata->get("agc.delayed_status", delayedStatus))
+		totalExposureValue = delayedStatus.totalExposureValue;
+
 	status_.digitalGain = 1.0;
 	fetchAwbStatus(imageMetadata); /* always fetch it so that Process knows it's been done */
 
@@ -418,8 +424,8 @@ void Agc::prepare(Metadata *imageMetadata)
 			Duration actualExposure = deviceStatus.shutterSpeed *
 						  deviceStatus.analogueGain;
 			if (actualExposure) {
-				status_.digitalGain = status_.totalExposureValue / actualExposure;
-				LOG(RPiAgc, Debug) << "Want total exposure " << status_.totalExposureValue;
+				status_.digitalGain = totalExposureValue / actualExposure;
+				LOG(RPiAgc, Debug) << "Want total exposure " << totalExposureValue;
 				/*
 				 * Never ask for a gain < 1.0, and also impose
 				 * some upper limit. Make it customisable?
diff --git a/src/ipa/raspberrypi/raspberrypi.cpp b/src/ipa/raspberrypi/raspberrypi.cpp
index 3faa3d490606..0c057f2689cc 100644
--- a/src/ipa/raspberrypi/raspberrypi.cpp
+++ b/src/ipa/raspberrypi/raspberrypi.cpp
@@ -1025,6 +1025,17 @@ void IPARPi::prepareISP(const ISPConfig &data)
 		embeddedBuffer = it->second.planes()[0];
 	}
 
+	/*
+	 * AGC wants to know the algorithm status from the time it actioned the
+	 * sensor exposure/gain changes. So fetch it from the metadata list
+	 * indexed by the IPA cookie returned, and put it in the current frame
+	 * metadata.
+	 */
+	AgcStatus agcStatus;
+	RPiController::Metadata &delayedMetadata = rpiMetadata_[data.ipaCookie];
+	if (!delayedMetadata.get<AgcStatus>("agc.status", agcStatus))
+		rpiMetadata.set("agc.delayed_status", agcStatus);
+
 	/*
 	 * This may overwrite the DeviceStatus using values from the sensor
 	 * metadata, and may also do additional custom processing.
-- 
2.25.1