From 57a46118a8a664e31b7b65b47948f29d55ee0746 Mon Sep 17 00:00:00 2001 From: Stefan Klug Date: Fri, 19 Sep 2025 11:40:24 +0200 Subject: [PATCH] libipa: exposure_mode_helper: Calculate quantization gain in splitExposure() Calculate the error introduced by quantization as "quantization gain" and return it separately from splitExposure(). It is not included in the digital gain, to not silently ignore the limits imposed by the AGC configuration. Signed-off-by: Stefan Klug Reviewed-by: Daniel Scally Reviewed-by: Paul Elder Signed-off-by: Kieran Bingham --- src/ipa/ipu3/algorithms/agc.cpp | 4 +- src/ipa/libipa/agc_mean_luminance.cpp | 7 ++-- src/ipa/libipa/agc_mean_luminance.h | 2 +- src/ipa/libipa/exposure_mode_helper.cpp | 51 +++++++++++++++++-------- src/ipa/libipa/exposure_mode_helper.h | 2 +- src/ipa/mali-c55/algorithms/agc.cpp | 4 +- src/ipa/rkisp1/algorithms/agc.cpp | 9 +++-- 7 files changed, 51 insertions(+), 28 deletions(-) diff --git a/src/ipa/ipu3/algorithms/agc.cpp b/src/ipa/ipu3/algorithms/agc.cpp index 39d0aebb..da045640 100644 --- a/src/ipa/ipu3/algorithms/agc.cpp +++ b/src/ipa/ipu3/algorithms/agc.cpp @@ -222,8 +222,8 @@ void Agc::process(IPAContext &context, [[maybe_unused]] const uint32_t frame, utils::Duration effectiveExposureValue = exposureTime * analogueGain; utils::Duration newExposureTime; - double aGain, dGain; - std::tie(newExposureTime, aGain, dGain) = + double aGain, qGain, dGain; + std::tie(newExposureTime, aGain, qGain, dGain) = calculateNewEv(context.activeState.agc.constraintMode, context.activeState.agc.exposureMode, hist, effectiveExposureValue); diff --git a/src/ipa/libipa/agc_mean_luminance.cpp b/src/ipa/libipa/agc_mean_luminance.cpp index ea4709bf..41c7f72d 100644 --- a/src/ipa/libipa/agc_mean_luminance.cpp +++ b/src/ipa/libipa/agc_mean_luminance.cpp @@ -566,11 +566,12 @@ utils::Duration AgcMeanLuminance::filterExposure(utils::Duration exposureValue) * * Calculate a new exposure value to try to obtain the target. The calculated * exposure value is filtered to prevent rapid changes from frame to frame, and - * divided into exposure time, analogue and digital gain. + * divided into exposure time, analogue, quantization and digital gain. * - * \return Tuple of exposure time, analogue gain, and digital gain + * \return Tuple of exposure time, analogue gain, quantization gain and digital + * gain */ -std::tuple +std::tuple AgcMeanLuminance::calculateNewEv(uint32_t constraintModeIndex, uint32_t exposureModeIndex, const Histogram &yHist, diff --git a/src/ipa/libipa/agc_mean_luminance.h b/src/ipa/libipa/agc_mean_luminance.h index 49985481..fbb526f6 100644 --- a/src/ipa/libipa/agc_mean_luminance.h +++ b/src/ipa/libipa/agc_mean_luminance.h @@ -68,7 +68,7 @@ public: return controls_; } - std::tuple + std::tuple calculateNewEv(uint32_t constraintModeIndex, uint32_t exposureModeIndex, const Histogram &yHist, utils::Duration effectiveExposureValue); diff --git a/src/ipa/libipa/exposure_mode_helper.cpp b/src/ipa/libipa/exposure_mode_helper.cpp index f2de1d8e..29e316d9 100644 --- a/src/ipa/libipa/exposure_mode_helper.cpp +++ b/src/ipa/libipa/exposure_mode_helper.cpp @@ -178,14 +178,24 @@ double ExposureModeHelper::clampGain(double gain, double *quantizationGain) cons * required exposure, the helper falls-back to simply maximising the exposure * time first, followed by analogue gain, followed by digital gain. * - * \return Tuple of exposure time, analogue gain, and digital gain + * During the calculations the gain missed due to quantization is recorded and + * returned as quantization gain. The quantization gain is not included in the + * digital gain. So to exactly apply the given exposure, both quantization gain + * and digital gain must be applied. + * + * \return Tuple of exposure time, analogue gain, quantization gain and digital + * gain */ -std::tuple +std::tuple ExposureModeHelper::splitExposure(utils::Duration exposure) const { ASSERT(maxExposureTime_); ASSERT(maxGain_); + utils::Duration exposureTime; + double gain; + double quantGain; + double quantGain2; bool gainFixed = minGain_ == maxGain_; bool exposureTimeFixed = minExposureTime_ == maxExposureTime_; @@ -193,16 +203,21 @@ ExposureModeHelper::splitExposure(utils::Duration exposure) const * There's no point entering the loop if we cannot change either gain * nor exposure time anyway. */ - if (exposureTimeFixed && gainFixed) - return { minExposureTime_, minGain_, exposure / (minExposureTime_ * minGain_) }; + if (exposureTimeFixed && gainFixed) { + exposureTime = clampExposureTime(minExposureTime_, &quantGain); + gain = clampGain(minGain_, &quantGain2); + quantGain *= quantGain2; + + return { exposureTime, gain, quantGain, + exposure / (exposureTime * gain * quantGain) }; + } - utils::Duration exposureTime; double stageGain = clampGain(1.0); double lastStageGain = stageGain; - double gain; for (unsigned int stage = 0; stage < gains_.size(); stage++) { - utils::Duration stageExposureTime = clampExposureTime(exposureTimes_[stage]); + utils::Duration stageExposureTime = clampExposureTime(exposureTimes_[stage], + &quantGain); stageGain = clampGain(gains_[stage]); /* @@ -215,18 +230,22 @@ ExposureModeHelper::splitExposure(utils::Duration exposure) const /* Clamp the gain to lastStageGain and regulate exposureTime. */ if (stageExposureTime * lastStageGain >= exposure) { - exposureTime = clampExposureTime(exposure / lastStageGain); - gain = clampGain(exposure / exposureTime); + exposureTime = clampExposureTime(exposure / lastStageGain, &quantGain); + gain = clampGain(exposure / exposureTime, &quantGain2); + quantGain *= quantGain2; - return { exposureTime, gain, exposure / (exposureTime * gain) }; + return { exposureTime, gain, quantGain, + exposure / (exposureTime * gain * quantGain) }; } /* Clamp the exposureTime to stageExposureTime and regulate gain. */ if (stageExposureTime * stageGain >= exposure) { exposureTime = stageExposureTime; - gain = clampGain(exposure / exposureTime); + gain = clampGain(exposure / exposureTime, &quantGain2); + quantGain *= quantGain2; - return { exposureTime, gain, exposure / (exposureTime * gain) }; + return { exposureTime, gain, quantGain, + exposure / (exposureTime * gain * quantGain) }; } lastStageGain = stageGain; @@ -239,10 +258,12 @@ ExposureModeHelper::splitExposure(utils::Duration exposure) const * stages to use then the default stageGain of 1.0 is used so that * exposure time is maxed before gain is touched at all. */ - exposureTime = clampExposureTime(exposure / stageGain); - gain = clampGain(exposure / exposureTime); + exposureTime = clampExposureTime(exposure / stageGain, &quantGain); + gain = clampGain(exposure / exposureTime, &quantGain2); + quantGain *= quantGain2; - return { exposureTime, gain, exposure / (exposureTime * gain) }; + return { exposureTime, gain, quantGain, + exposure / (exposureTime * gain * quantGain) }; } /** diff --git a/src/ipa/libipa/exposure_mode_helper.h b/src/ipa/libipa/exposure_mode_helper.h index ac7e8da9..968192dd 100644 --- a/src/ipa/libipa/exposure_mode_helper.h +++ b/src/ipa/libipa/exposure_mode_helper.h @@ -30,7 +30,7 @@ public: void setLimits(utils::Duration minExposureTime, utils::Duration maxExposureTime, double minGain, double maxGain); - std::tuple + std::tuple splitExposure(utils::Duration exposure) const; utils::Duration minExposureTime() const { return minExposureTime_; } diff --git a/src/ipa/mali-c55/algorithms/agc.cpp b/src/ipa/mali-c55/algorithms/agc.cpp index 15963994..88f8664c 100644 --- a/src/ipa/mali-c55/algorithms/agc.cpp +++ b/src/ipa/mali-c55/algorithms/agc.cpp @@ -381,8 +381,8 @@ void Agc::process(IPAContext &context, utils::Duration effectiveExposureValue = currentShutter * totalGain; utils::Duration shutterTime; - double aGain, dGain; - std::tie(shutterTime, aGain, dGain) = + double aGain, qGain, dGain; + std::tie(shutterTime, aGain, qGain, dGain) = calculateNewEv(activeState.agc.constraintMode, activeState.agc.exposureMode, statistics_.yHist, effectiveExposureValue); diff --git a/src/ipa/rkisp1/algorithms/agc.cpp b/src/ipa/rkisp1/algorithms/agc.cpp index 35440b67..0a293268 100644 --- a/src/ipa/rkisp1/algorithms/agc.cpp +++ b/src/ipa/rkisp1/algorithms/agc.cpp @@ -567,15 +567,16 @@ void Agc::process(IPAContext &context, [[maybe_unused]] const uint32_t frame, setExposureCompensation(pow(2.0, frameContext.agc.exposureValue)); utils::Duration newExposureTime; - double aGain, dGain; - std::tie(newExposureTime, aGain, dGain) = + double aGain, qGain, dGain; + std::tie(newExposureTime, aGain, qGain, dGain) = calculateNewEv(frameContext.agc.constraintMode, frameContext.agc.exposureMode, hist, effectiveExposureValue); LOG(RkISP1Agc, Debug) - << "Divided up exposure time, analogue gain and digital gain are " - << newExposureTime << ", " << aGain << " and " << dGain; + << "Divided up exposure time, analogue gain, quantization gain" + << " and digital gain are " << newExposureTime << ", " << aGain + << ", " << qGain << " and " << dGain; IPAActiveState &activeState = context.activeState; /* Update the estimated exposure and gain. */