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ipa: rkisp1: agc: Add correction for exposure quantization

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There are several occasions where quantization can lead to visible
effects.

In WDR mode it can happen that exposure times get set to very low values
(Sometimes 2-3 lines). This intentionally introduced underexposure is
corrected by the GWDR module. As exposure time is quantized by lines,
the smallest possible change in exposure time now results in a quite
visible change in perceived brightness.

On some sensors the possible gain steps are also quite large leading to
visible jumps if e.g. if the exposure time is fixed.

Mitigate that by applying a global gain to account for the error
introduced by the exposure quantization.

ToDo: This needs perfect frame synchronous control of the sensor to work
properly which is not guaranteed in all cases. It still improves the
behavior with the current regulation and can easily be skipped, be
removing the compress algorithm from the tuning file.

Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Daniel Scally <dan.scally@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
This commit is contained in:
Stefan Klug
2025-09-19 11:40:25 +02:00
committed by Kieran Bingham
parent 57a46118a8
commit ef830669d0
2 changed files with 32 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

33
src/ipa/rkisp1/algorithms/agc.cpp
View File

@@ -176,6 +176,7 @@ int Agc::configure(IPAContext &context, const IPACameraSensorInfo &configInfo)
context.activeState.agc.automatic.gain = context.configuration.sensor.minAnalogueGain;
context.activeState.agc.automatic.exposure =
10ms / context.configuration.sensor.lineDuration;
context.activeState.agc.automatic.quantizationGain = 1.0;
context.activeState.agc.manual.gain = context.activeState.agc.automatic.gain;
context.activeState.agc.manual.exposure = context.activeState.agc.automatic.exposure;
context.activeState.agc.autoExposureEnabled = !context.configuration.raw;
@@ -199,6 +200,9 @@ int Agc::configure(IPAContext &context, const IPACameraSensorInfo &configInfo)
context.configuration.agc.measureWindow.h_size = configInfo.outputSize.width;
context.configuration.agc.measureWindow.v_size = configInfo.outputSize.height;
AgcMeanLuminance::configure(context.configuration.sensor.lineDuration,
context.camHelper.get());
setLimits(context.configuration.sensor.minExposureTime,
context.configuration.sensor.maxExposureTime,
context.configuration.sensor.minAnalogueGain,
@@ -283,6 +287,10 @@ void Agc::queueRequest(IPAContext &context,
if (!frameContext.agc.autoGainEnabled)
frameContext.agc.gain = agc.manual.gain;
if (!frameContext.agc.autoExposureEnabled &&
!frameContext.agc.autoGainEnabled)
frameContext.agc.quantizationGain = 1.0;
const auto &meteringMode = controls.get(controls::AeMeteringMode);
if (meteringMode) {
frameContext.agc.updateMetering = agc.meteringMode != *meteringMode;
@@ -336,12 +344,17 @@ void Agc::prepare(IPAContext &context, const uint32_t frame,
{
uint32_t activeAutoExposure = context.activeState.agc.automatic.exposure;
double activeAutoGain = context.activeState.agc.automatic.gain;
double activeAutoQGain = context.activeState.agc.automatic.quantizationGain;
/* Populate exposure and gain in auto mode */
if (frameContext.agc.autoExposureEnabled)
if (frameContext.agc.autoExposureEnabled) {
frameContext.agc.exposure = activeAutoExposure;
if (frameContext.agc.autoGainEnabled)
frameContext.agc.quantizationGain = activeAutoQGain;
}
if (frameContext.agc.autoGainEnabled) {
frameContext.agc.gain = activeAutoGain;
frameContext.agc.quantizationGain = activeAutoQGain;
}
/*
* Populate manual exposure and gain from the active auto values when
@@ -354,6 +367,12 @@ void Agc::prepare(IPAContext &context, const uint32_t frame,
if (!frameContext.agc.autoGainEnabled && frameContext.agc.autoGainModeChange) {
context.activeState.agc.manual.gain = activeAutoGain;
frameContext.agc.gain = activeAutoGain;
frameContext.agc.quantizationGain = activeAutoQGain;
}
if (context.configuration.compress.supported) {
frameContext.compress.enable = true;
frameContext.compress.gain = frameContext.agc.quantizationGain;
}
if (frame > 0 && !frameContext.agc.updateMetering)
@@ -564,6 +583,14 @@ void Agc::process(IPAContext &context, [[maybe_unused]] const uint32_t frame,
double analogueGain = frameContext.sensor.gain;
utils::Duration effectiveExposureValue = exposureTime * analogueGain;
/*
* Include the quantization gain if it was applied. Do not use
* compress.gain because it will include gains that shall not be
* reported to the user when HDR is implemented.
*/
if (frameContext.compress.enable)
effectiveExposureValue *= frameContext.agc.quantizationGain;
setExposureCompensation(pow(2.0, frameContext.agc.exposureValue));
utils::Duration newExposureTime;
@@ -582,7 +609,7 @@ void Agc::process(IPAContext &context, [[maybe_unused]] const uint32_t frame,
/* Update the estimated exposure and gain. */
activeState.agc.automatic.exposure = newExposureTime / lineDuration;
activeState.agc.automatic.gain = aGain;
activeState.agc.automatic.quantizationGain = qGain;
/*
* Expand the target frame duration so that we do not run faster than
* the minimum frame duration when we have short exposures.

2
src/ipa/rkisp1/ipa_context.h
View File

@@ -81,6 +81,7 @@ struct IPAActiveState {
struct {
uint32_t exposure;
double gain;
double quantizationGain;
} automatic;
bool autoExposureEnabled;
@@ -135,6 +136,7 @@ struct IPAFrameContext : public FrameContext {
uint32_t exposure;
double gain;
double exposureValue;
double quantizationGain;
uint32_t vblank;
bool autoExposureEnabled;
bool autoGainEnabled;