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Diffstat (limited to 'src/ipa/libipa/agc_mean_luminance.cpp')
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diff --git a/src/ipa/libipa/agc_mean_luminance.cpp b/src/ipa/libipa/agc_mean_luminance.cpp new file mode 100644 index 00000000..2bf84d05 --- /dev/null +++ b/src/ipa/libipa/agc_mean_luminance.cpp @@ -0,0 +1,577 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ +/* + * Copyright (C) 2024 Ideas on Board Oy + * + * agc_mean_luminance.cpp - Base class for mean luminance AGC algorithms + */ + +#include "agc_mean_luminance.h" + +#include <cmath> + +#include <libcamera/base/log.h> +#include <libcamera/control_ids.h> + +#include "exposure_mode_helper.h" + +using namespace libcamera::controls; + +/** + * \file agc_mean_luminance.h + * \brief Base class implementing mean luminance AEGC + */ + +namespace libcamera { + +using namespace std::literals::chrono_literals; + +LOG_DEFINE_CATEGORY(AgcMeanLuminance) + +namespace ipa { + +/* + * Number of frames for which to run the algorithm at full speed, before slowing + * down to prevent large and jarring changes in exposure from frame to frame. + */ +static constexpr uint32_t kNumStartupFrames = 10; + +/* + * Default relative luminance target + * + * This value should be chosen so that when the camera points at a grey target, + * the resulting image brightness looks "right". Custom values can be passed + * as the relativeLuminanceTarget value in sensor tuning files. + */ +static constexpr double kDefaultRelativeLuminanceTarget = 0.16; + +/** + * \struct AgcMeanLuminance::AgcConstraint + * \brief The boundaries and target for an AeConstraintMode constraint + * + * This structure describes an AeConstraintMode constraint for the purposes of + * this algorithm. These constraints are expressed as a pair of quantile + * boundaries for a histogram, along with a luminance target and a bounds-type. + * The algorithm uses the constraints by ensuring that the defined portion of a + * luminance histogram (I.E. lying between the two quantiles) is above or below + * the given luminance value. + */ + +/** + * \enum AgcMeanLuminance::AgcConstraint::Bound + * \brief Specify whether the constraint defines a lower or upper bound + * \var AgcMeanLuminance::AgcConstraint::lower + * \brief The constraint defines a lower bound + * \var AgcMeanLuminance::AgcConstraint::upper + * \brief The constraint defines an upper bound + */ + +/** + * \var AgcMeanLuminance::AgcConstraint::bound + * \brief The type of constraint bound + */ + +/** + * \var AgcMeanLuminance::AgcConstraint::qLo + * \brief The lower quantile to use for the constraint + */ + +/** + * \var AgcMeanLuminance::AgcConstraint::qHi + * \brief The upper quantile to use for the constraint + */ + +/** + * \var AgcMeanLuminance::AgcConstraint::yTarget + * \brief The luminance target for the constraint + */ + +/** + * \class AgcMeanLuminance + * \brief A mean-based auto-exposure algorithm + * + * This algorithm calculates a shutter time, analogue and digital gain such that + * the normalised mean luminance value of an image is driven towards a target, + * which itself is discovered from tuning data. The algorithm is a two-stage + * process. + * + * In the first stage, an initial gain value is derived by iteratively comparing + * the gain-adjusted mean luminance across the entire image against a target, + * and selecting a value which pushes it as closely as possible towards the + * target. + * + * In the second stage we calculate the gain required to drive the average of a + * section of a histogram to a target value, where the target and the boundaries + * of the section of the histogram used in the calculation are taken from the + * values defined for the currently configured AeConstraintMode within the + * tuning data. This class provides a helper function to parse those tuning data + * to discover the constraints, and so requires a specific format for those + * data which is described in \ref parseTuningData(). The gain from the first + * stage is then clamped to the gain from this stage. + * + * The final gain is used to adjust the effective exposure value of the image, + * and that new exposure value is divided into shutter time, analogue gain and + * digital gain according to the selected AeExposureMode. This class uses the + * \ref ExposureModeHelper class to assist in that division, and expects the + * data needed to initialise that class to be present in tuning data in a + * format described in \ref parseTuningData(). + * + * In order to be able to use this algorithm an IPA module needs to be able to + * do the following: + * + * 1. Provide a luminance estimation across an entire image. + * 2. Provide a luminance Histogram for the image to use in calculating + * constraint compliance. The precision of the Histogram that is available + * will determine the supportable precision of the constraints. + * + * IPA modules that want to use this class to implement their AEGC algorithm + * should derive it and provide an overriding estimateLuminance() function for + * this class to use. They must call parseTuningData() in init(), and must also + * call setLimits() and resetFrameCounter() in configure(). They may then use + * calculateNewEv() in process(). If the limits passed to setLimits() change for + * any reason (for example, in response to a FrameDurationLimit control being + * passed in queueRequest()) then setLimits() must be called again with the new + * values. + */ + +AgcMeanLuminance::AgcMeanLuminance() + : frameCount_(0), filteredExposure_(0s), relativeLuminanceTarget_(0) +{ +} + +AgcMeanLuminance::~AgcMeanLuminance() = default; + +void AgcMeanLuminance::parseRelativeLuminanceTarget(const YamlObject &tuningData) +{ + relativeLuminanceTarget_ = + tuningData["relativeLuminanceTarget"].get<double>(kDefaultRelativeLuminanceTarget); +} + +void AgcMeanLuminance::parseConstraint(const YamlObject &modeDict, int32_t id) +{ + for (const auto &[boundName, content] : modeDict.asDict()) { + if (boundName != "upper" && boundName != "lower") { + LOG(AgcMeanLuminance, Warning) + << "Ignoring unknown constraint bound '" << boundName << "'"; + continue; + } + + unsigned int idx = static_cast<unsigned int>(boundName == "upper"); + AgcConstraint::Bound bound = static_cast<AgcConstraint::Bound>(idx); + double qLo = content["qLo"].get<double>().value_or(0.98); + double qHi = content["qHi"].get<double>().value_or(1.0); + double yTarget = + content["yTarget"].getList<double>().value_or(std::vector<double>{ 0.5 }).at(0); + + AgcConstraint constraint = { bound, qLo, qHi, yTarget }; + + if (!constraintModes_.count(id)) + constraintModes_[id] = {}; + + if (idx) + constraintModes_[id].push_back(constraint); + else + constraintModes_[id].insert(constraintModes_[id].begin(), constraint); + } +} + +int AgcMeanLuminance::parseConstraintModes(const YamlObject &tuningData) +{ + std::vector<ControlValue> availableConstraintModes; + + const YamlObject &yamlConstraintModes = tuningData[controls::AeConstraintMode.name()]; + if (yamlConstraintModes.isDictionary()) { + for (const auto &[modeName, modeDict] : yamlConstraintModes.asDict()) { + if (AeConstraintModeNameValueMap.find(modeName) == + AeConstraintModeNameValueMap.end()) { + LOG(AgcMeanLuminance, Warning) + << "Skipping unknown constraint mode '" << modeName << "'"; + continue; + } + + if (!modeDict.isDictionary()) { + LOG(AgcMeanLuminance, Error) + << "Invalid constraint mode '" << modeName << "'"; + return -EINVAL; + } + + parseConstraint(modeDict, + AeConstraintModeNameValueMap.at(modeName)); + availableConstraintModes.push_back( + AeConstraintModeNameValueMap.at(modeName)); + } + } + + /* + * If the tuning data file contains no constraints then we use the + * default constraint that the IPU3/RkISP1 Agc algorithms were adhering + * to anyway before centralisation; this constraint forces the top 2% of + * the histogram to be at least 0.5. + */ + if (constraintModes_.empty()) { + AgcConstraint constraint = { + AgcConstraint::Bound::lower, + 0.98, + 1.0, + 0.5 + }; + + constraintModes_[controls::ConstraintNormal].insert( + constraintModes_[controls::ConstraintNormal].begin(), + constraint); + availableConstraintModes.push_back( + AeConstraintModeNameValueMap.at("ConstraintNormal")); + } + + controls_[&controls::AeConstraintMode] = ControlInfo(availableConstraintModes); + + return 0; +} + +int AgcMeanLuminance::parseExposureModes(const YamlObject &tuningData) +{ + std::vector<ControlValue> availableExposureModes; + + const YamlObject &yamlExposureModes = tuningData[controls::AeExposureMode.name()]; + if (yamlExposureModes.isDictionary()) { + for (const auto &[modeName, modeValues] : yamlExposureModes.asDict()) { + if (AeExposureModeNameValueMap.find(modeName) == + AeExposureModeNameValueMap.end()) { + LOG(AgcMeanLuminance, Warning) + << "Skipping unknown exposure mode '" << modeName << "'"; + continue; + } + + if (!modeValues.isDictionary()) { + LOG(AgcMeanLuminance, Error) + << "Invalid exposure mode '" << modeName << "'"; + return -EINVAL; + } + + std::vector<uint32_t> shutters = + modeValues["shutter"].getList<uint32_t>().value_or(std::vector<uint32_t>{}); + std::vector<double> gains = + modeValues["gain"].getList<double>().value_or(std::vector<double>{}); + + if (shutters.size() != gains.size()) { + LOG(AgcMeanLuminance, Error) + << "Shutter and gain array sizes unequal"; + return -EINVAL; + } + + if (shutters.empty()) { + LOG(AgcMeanLuminance, Error) + << "Shutter and gain arrays are empty"; + return -EINVAL; + } + + std::vector<std::pair<utils::Duration, double>> stages; + for (unsigned int i = 0; i < shutters.size(); i++) { + stages.push_back({ + std::chrono::microseconds(shutters[i]), + gains[i] + }); + } + + std::shared_ptr<ExposureModeHelper> helper = + std::make_shared<ExposureModeHelper>(stages); + + exposureModeHelpers_[AeExposureModeNameValueMap.at(modeName)] = helper; + availableExposureModes.push_back(AeExposureModeNameValueMap.at(modeName)); + } + } + + /* + * If we don't have any exposure modes in the tuning data we create an + * ExposureModeHelper using an empty vector of stages. This will result + * in the ExposureModeHelper simply driving the shutter as high as + * possible before touching gain. + */ + if (availableExposureModes.empty()) { + int32_t exposureModeId = AeExposureModeNameValueMap.at("ExposureNormal"); + std::vector<std::pair<utils::Duration, double>> stages = { }; + + std::shared_ptr<ExposureModeHelper> helper = + std::make_shared<ExposureModeHelper>(stages); + + exposureModeHelpers_[exposureModeId] = helper; + availableExposureModes.push_back(exposureModeId); + } + + controls_[&controls::AeExposureMode] = ControlInfo(availableExposureModes); + + return 0; +} + +/** + * \brief Parse tuning data for AeConstraintMode and AeExposureMode controls + * \param[in] tuningData the YamlObject representing the tuning data + * + * This function parses tuning data to build the list of allowed values for the + * AeConstraintMode and AeExposureMode controls. Those tuning data must provide + * the data in a specific format; the Agc algorithm's tuning data should contain + * a dictionary called AeConstraintMode containing per-mode setting dictionaries + * with the key being a value from \ref controls::AeConstraintModeNameValueMap. + * Each mode dict may contain either a "lower" or "upper" key or both, for + * example: + * + * \code{.unparsed} + * algorithms: + * - Agc: + * AeConstraintMode: + * ConstraintNormal: + * lower: + * qLo: 0.98 + * qHi: 1.0 + * yTarget: 0.5 + * ConstraintHighlight: + * lower: + * qLo: 0.98 + * qHi: 1.0 + * yTarget: 0.5 + * upper: + * qLo: 0.98 + * qHi: 1.0 + * yTarget: 0.8 + * + * \endcode + * + * For the AeExposureMode control the data should contain a dictionary called + * AeExposureMode containing per-mode setting dictionaries with the key being a + * value from \ref controls::AeExposureModeNameValueMap. Each mode dict should + * contain an array of shutter times with the key "shutter" and an array of gain + * values with the key "gain", in this format: + * + * \code{.unparsed} + * algorithms: + * - Agc: + * AeExposureMode: + * ExposureNormal: + * shutter: [ 100, 10000, 30000, 60000, 120000 ] + * gain: [ 2.0, 4.0, 6.0, 8.0, 10.0 ] + * ExposureShort: + * shutter: [ 100, 10000, 30000, 60000, 120000 ] + * gain: [ 2.0, 4.0, 6.0, 8.0, 10.0 ] + * + * \endcode + * + * \return 0 on success or a negative error code + */ +int AgcMeanLuminance::parseTuningData(const YamlObject &tuningData) +{ + int ret; + + parseRelativeLuminanceTarget(tuningData); + + ret = parseConstraintModes(tuningData); + if (ret) + return ret; + + return parseExposureModes(tuningData); +} + +/** + * \brief Set the ExposureModeHelper limits for this class + * \param[in] minShutter Minimum shutter time to allow + * \param[in] maxShutter Maximum shutter time to allow + * \param[in] minGain Minimum gain to allow + * \param[in] maxGain Maximum gain to allow + * + * This function calls \ref ExposureModeHelper::setLimits() for each + * ExposureModeHelper that has been created for this class. + */ +void AgcMeanLuminance::setLimits(utils::Duration minShutter, + utils::Duration maxShutter, + double minGain, double maxGain) +{ + for (auto &[id, helper] : exposureModeHelpers_) + helper->setLimits(minShutter, maxShutter, minGain, maxGain); +} + +/** + * \fn AgcMeanLuminance::constraintModes() + * \brief Get the constraint modes that have been parsed from tuning data + */ + +/** + * \fn AgcMeanLuminance::exposureModeHelpers() + * \brief Get the ExposureModeHelpers that have been parsed from tuning data + */ + +/** + * \fn AgcMeanLuminance::controls() + * \brief Get the controls that have been generated after parsing tuning data + */ + +/** + * \fn AgcMeanLuminance::estimateLuminance(const double gain) + * \brief Estimate the luminance of an image, adjusted by a given gain + * \param[in] gain The gain with which to adjust the luminance estimate + * + * This function estimates the average relative luminance of the frame that + * would be output by the sensor if an additional \a gain was applied. It is a + * pure virtual function because estimation of luminance is a hardware-specific + * operation, which depends wholly on the format of the stats that are delivered + * to libcamera from the ISP. Derived classes must override this function with + * one that calculates the normalised mean luminance value across the entire + * image. + * + * \return The normalised relative luminance of the image + */ + +/** + * \brief Estimate the initial gain needed to achieve a relative luminance + * target + * \return The calculated initial gain + */ +double AgcMeanLuminance::estimateInitialGain() const +{ + double yTarget = relativeLuminanceTarget_; + double yGain = 1.0; + + /* + * To account for non-linearity caused by saturation, the value needs to + * be estimated in an iterative process, as multiplying by a gain will + * not increase the relative luminance by the same factor if some image + * regions are saturated. + */ + for (unsigned int i = 0; i < 8; i++) { + double yValue = estimateLuminance(yGain); + double extra_gain = std::min(10.0, yTarget / (yValue + .001)); + + yGain *= extra_gain; + LOG(AgcMeanLuminance, Debug) << "Y value: " << yValue + << ", Y target: " << yTarget + << ", gives gain " << yGain; + + if (utils::abs_diff(extra_gain, 1.0) < 0.01) + break; + } + + return yGain; +} + +/** + * \brief Clamp gain within the bounds of a defined constraint + * \param[in] constraintModeIndex The index of the constraint to adhere to + * \param[in] hist A histogram over which to calculate inter-quantile means + * \param[in] gain The gain to clamp + * + * \return The gain clamped within the constraint bounds + */ +double AgcMeanLuminance::constraintClampGain(uint32_t constraintModeIndex, + const Histogram &hist, + double gain) +{ + std::vector<AgcConstraint> &constraints = constraintModes_[constraintModeIndex]; + for (const AgcConstraint &constraint : constraints) { + double newGain = constraint.yTarget * hist.bins() / + hist.interQuantileMean(constraint.qLo, constraint.qHi); + + if (constraint.bound == AgcConstraint::Bound::lower && + newGain > gain) + gain = newGain; + + if (constraint.bound == AgcConstraint::Bound::upper && + newGain < gain) + gain = newGain; + } + + return gain; +} + +/** + * \brief Apply a filter on the exposure value to limit the speed of changes + * \param[in] exposureValue The target exposure from the AGC algorithm + * + * The speed of the filter is adaptive, and will produce the target quicker + * during startup, or when the target exposure is within 20% of the most recent + * filter output. + * + * \return The filtered exposure + */ +utils::Duration AgcMeanLuminance::filterExposure(utils::Duration exposureValue) +{ + double speed = 0.2; + + /* Adapt instantly if we are in startup phase. */ + if (frameCount_ < kNumStartupFrames) + speed = 1.0; + + /* + * If we are close to the desired result, go faster to avoid making + * multiple micro-adjustments. + * \todo Make this customisable? + */ + if (filteredExposure_ < 1.2 * exposureValue && + filteredExposure_ > 0.8 * exposureValue) + speed = sqrt(speed); + + filteredExposure_ = speed * exposureValue + + filteredExposure_ * (1.0 - speed); + + return filteredExposure_; +} + +/** + * \brief Calculate the new exposure value and splut it between shutter time and gain + * \param[in] constraintModeIndex The index of the current constraint mode + * \param[in] exposureModeIndex The index of the current exposure mode + * \param[in] yHist A Histogram from the ISP statistics to use in constraining + * the calculated gain + * \param[in] effectiveExposureValue The EV applied to the frame from which the + * statistics in use derive + * + * 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 shutter time, analogue and digital gain. + * + * \return Tuple of shutter time, analogue gain, and digital gain + */ +std::tuple<utils::Duration, double, double> +AgcMeanLuminance::calculateNewEv(uint32_t constraintModeIndex, + uint32_t exposureModeIndex, + const Histogram &yHist, + utils::Duration effectiveExposureValue) +{ + /* + * The pipeline handler should validate that we have received an allowed + * value for AeExposureMode. + */ + std::shared_ptr<ExposureModeHelper> exposureModeHelper = + exposureModeHelpers_.at(exposureModeIndex); + + double gain = estimateInitialGain(); + gain = constraintClampGain(constraintModeIndex, yHist, gain); + + /* + * We don't check whether we're already close to the target, because + * even if the effective exposure value is the same as the last frame's + * we could have switched to an exposure mode that would require a new + * pass through the splitExposure() function. + */ + + utils::Duration newExposureValue = effectiveExposureValue * gain; + + /* + * We filter the exposure value to make sure changes are not too jarring + * from frame to frame. + */ + newExposureValue = filterExposure(newExposureValue); + + frameCount_++; + return exposureModeHelper->splitExposure(newExposureValue); +} + +/** + * \fn AgcMeanLuminance::resetFrameCount() + * \brief Reset the frame counter + * + * This function resets the internal frame counter, which exists to help the + * algorithm decide whether it should respond instantly or not. The expectation + * is for derived classes to call this function before each camera start call in + * their configure() function. + */ + +} /* namespace ipa */ + +} /* namespace libcamera */ |