From 7b5d8bc84902463e31bfc6150178dd67b2e1b5ec Mon Sep 17 00:00:00 2001 From: Stefan Klug Date: Mon, 7 Jul 2025 10:55:11 +0200 Subject: [PATCH] libipa: agc_mean_luminance: Add exposure compensation support Exposure compensation allows to over- or under-expose an image by a given value. Add support for that in agc_mean_luminance. The added exposure compensation can lead to luminance target values that are close or above saturation and are therefore never reachable. Add a fix for that by limiting the maximum luminance target to 0.95. Signed-off-by: Stefan Klug Reviewed-by: Daniel Scally Reviewed-by: Paul Elder --- src/ipa/libipa/agc_mean_luminance.cpp | 24 ++++++++++++++++++++++-- src/ipa/libipa/agc_mean_luminance.h | 6 ++++++ 2 files changed, 28 insertions(+), 2 deletions(-) diff --git a/src/ipa/libipa/agc_mean_luminance.cpp b/src/ipa/libipa/agc_mean_luminance.cpp index ebdb4d75..ff96a381 100644 --- a/src/ipa/libipa/agc_mean_luminance.cpp +++ b/src/ipa/libipa/agc_mean_luminance.cpp @@ -44,6 +44,15 @@ static constexpr uint32_t kNumStartupFrames = 10; */ static constexpr double kDefaultRelativeLuminanceTarget = 0.16; +/* + * Maximum relative luminance target + * + * This value limits the relative luminance target after applying the exposure + * compensation. Targeting a value above this limit results in saturation + * and the inability to regulate properly. + */ +static constexpr double kMaxRelativeLuminanceTarget = 0.95; + /** * \struct AgcMeanLuminance::AgcConstraint * \brief The boundaries and target for an AeConstraintMode constraint @@ -134,7 +143,8 @@ static constexpr double kDefaultRelativeLuminanceTarget = 0.16; */ AgcMeanLuminance::AgcMeanLuminance() - : frameCount_(0), filteredExposure_(0s), relativeLuminanceTarget_(0) + : exposureCompensation_(1.0), frameCount_(0), filteredExposure_(0s), + relativeLuminanceTarget_(0) { } @@ -368,6 +378,15 @@ int AgcMeanLuminance::parseTuningData(const YamlObject &tuningData) return parseExposureModes(tuningData); } +/** + * \fn AgcMeanLuminance::setExposureCompensation() + * \brief Set the exposure compensation value + * \param[in] gain The exposure compensation gain + * + * This function sets the exposure compensation value to be used in the + * AGC calculations. It is expressed as gain instead of EV. + */ + /** * \brief Set the ExposureModeHelper limits for this class * \param[in] minExposureTime Minimum exposure time to allow @@ -424,7 +443,8 @@ void AgcMeanLuminance::setLimits(utils::Duration minExposureTime, */ double AgcMeanLuminance::estimateInitialGain() const { - double yTarget = relativeLuminanceTarget_; + double yTarget = std::min(relativeLuminanceTarget_ * exposureCompensation_, + kMaxRelativeLuminanceTarget); double yGain = 1.0; /* diff --git a/src/ipa/libipa/agc_mean_luminance.h b/src/ipa/libipa/agc_mean_luminance.h index c41391cb..cad7ef84 100644 --- a/src/ipa/libipa/agc_mean_luminance.h +++ b/src/ipa/libipa/agc_mean_luminance.h @@ -44,6 +44,11 @@ public: int parseTuningData(const YamlObject &tuningData); + void setExposureCompensation(double gain) + { + exposureCompensation_ = gain; + } + void setLimits(utils::Duration minExposureTime, utils::Duration maxExposureTime, double minGain, double maxGain); @@ -84,6 +89,7 @@ private: double gain); utils::Duration filterExposure(utils::Duration exposureValue); + double exposureCompensation_; uint64_t frameCount_; utils::Duration filteredExposure_; double relativeLuminanceTarget_;