From fb8ad13dc3e38a1bb056c209f692af53588c7b84 Mon Sep 17 00:00:00 2001 From: Milan Zamazal Date: Fri, 27 Sep 2024 15:46:23 +0200 Subject: libcamera: software_isp: Move exposure+gain to an algorithm module This is the last step to fully convert software ISP to Algorithm-based processing. The newly introduced frameContext.sensor parameters are set, and the updated code moved, before calling Algorithm::process() to have the values up-to-date in stats processing. Resolves software ISP TODO #10. Signed-off-by: Milan Zamazal Reviewed-by: Kieran Bingham Reviewed-by: Umang Jain Signed-off-by: Kieran Bingham --- src/ipa/simple/algorithms/agc.cpp | 139 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 139 insertions(+) create mode 100644 src/ipa/simple/algorithms/agc.cpp (limited to 'src/ipa/simple/algorithms/agc.cpp') diff --git a/src/ipa/simple/algorithms/agc.cpp b/src/ipa/simple/algorithms/agc.cpp new file mode 100644 index 00000000..783dfb8b --- /dev/null +++ b/src/ipa/simple/algorithms/agc.cpp @@ -0,0 +1,139 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ +/* + * Copyright (C) 2024, Red Hat Inc. + * + * Exposure and gain + */ + +#include "agc.h" + +#include + +#include + +namespace libcamera { + +LOG_DEFINE_CATEGORY(IPASoftExposure) + +namespace ipa::soft::algorithms { + +/* + * The number of bins to use for the optimal exposure calculations. + */ +static constexpr unsigned int kExposureBinsCount = 5; + +/* + * The exposure is optimal when the mean sample value of the histogram is + * in the middle of the range. + */ +static constexpr float kExposureOptimal = kExposureBinsCount / 2.0; + +/* + * The below value implements the hysteresis for the exposure adjustment. + * It is small enough to have the exposure close to the optimal, and is big + * enough to prevent the exposure from wobbling around the optimal value. + */ +static constexpr float kExposureSatisfactory = 0.2; + +Agc::Agc() +{ +} + +void Agc::updateExposure(IPAContext &context, double exposureMSV) +{ + /* + * kExpDenominator of 10 gives ~10% increment/decrement; + * kExpDenominator of 5 - about ~20% + */ + static constexpr uint8_t kExpDenominator = 10; + static constexpr uint8_t kExpNumeratorUp = kExpDenominator + 1; + static constexpr uint8_t kExpNumeratorDown = kExpDenominator - 1; + + double next; + int32_t &exposure = context.activeState.agc.exposure; + double &again = context.activeState.agc.again; + + if (exposureMSV < kExposureOptimal - kExposureSatisfactory) { + next = exposure * kExpNumeratorUp / kExpDenominator; + if (next - exposure < 1) + exposure += 1; + else + exposure = next; + if (exposure >= context.configuration.agc.exposureMax) { + next = again * kExpNumeratorUp / kExpDenominator; + if (next - again < context.configuration.agc.againMinStep) + again += context.configuration.agc.againMinStep; + else + again = next; + } + } + + if (exposureMSV > kExposureOptimal + kExposureSatisfactory) { + if (exposure == context.configuration.agc.exposureMax && + again > context.configuration.agc.againMin) { + next = again * kExpNumeratorDown / kExpDenominator; + if (again - next < context.configuration.agc.againMinStep) + again -= context.configuration.agc.againMinStep; + else + again = next; + } else { + next = exposure * kExpNumeratorDown / kExpDenominator; + if (exposure - next < 1) + exposure -= 1; + else + exposure = next; + } + } + + exposure = std::clamp(exposure, context.configuration.agc.exposureMin, + context.configuration.agc.exposureMax); + again = std::clamp(again, context.configuration.agc.againMin, + context.configuration.agc.againMax); + + LOG(IPASoftExposure, Debug) + << "exposureMSV " << exposureMSV + << " exp " << exposure << " again " << again; +} + +void Agc::process(IPAContext &context, + [[maybe_unused]] const uint32_t frame, + [[maybe_unused]] IPAFrameContext &frameContext, + const SwIspStats *stats, + [[maybe_unused]] ControlList &metadata) +{ + /* + * Calculate Mean Sample Value (MSV) according to formula from: + * https://www.araa.asn.au/acra/acra2007/papers/paper84final.pdf + */ + const auto &histogram = stats->yHistogram; + const unsigned int blackLevelHistIdx = + context.activeState.blc.level / (256 / SwIspStats::kYHistogramSize); + const unsigned int histogramSize = + SwIspStats::kYHistogramSize - blackLevelHistIdx; + const unsigned int yHistValsPerBin = histogramSize / kExposureBinsCount; + const unsigned int yHistValsPerBinMod = + histogramSize / (histogramSize % kExposureBinsCount + 1); + int exposureBins[kExposureBinsCount] = {}; + unsigned int denom = 0; + unsigned int num = 0; + + for (unsigned int i = 0; i < histogramSize; i++) { + unsigned int idx = (i - (i / yHistValsPerBinMod)) / yHistValsPerBin; + exposureBins[idx] += histogram[blackLevelHistIdx + i]; + } + + for (unsigned int i = 0; i < kExposureBinsCount; i++) { + LOG(IPASoftExposure, Debug) << i << ": " << exposureBins[i]; + denom += exposureBins[i]; + num += exposureBins[i] * (i + 1); + } + + float exposureMSV = (denom == 0 ? 0 : static_cast(num) / denom); + updateExposure(context, exposureMSV); +} + +REGISTER_IPA_ALGORITHM(Agc, "Agc") + +} /* namespace ipa::soft::algorithms */ + +} /* namespace libcamera */ -- cgit v1.2.1