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Diffstat (limited to 'src/ipa/ipu3/algorithms/agc.cpp')
| -rw-r--r-- | src/ipa/ipu3/algorithms/agc.cpp | 255 |
1 files changed, 255 insertions, 0 deletions
diff --git a/src/ipa/ipu3/algorithms/agc.cpp b/src/ipa/ipu3/algorithms/agc.cpp new file mode 100644 index 00000000..39d0aebb --- /dev/null +++ b/src/ipa/ipu3/algorithms/agc.cpp @@ -0,0 +1,255 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ +/* + * Copyright (C) 2021, Ideas On Board + * + * AGC/AEC mean-based control algorithm + */ + +#include "agc.h" + +#include <algorithm> +#include <chrono> + +#include <libcamera/base/log.h> +#include <libcamera/base/utils.h> + +#include <libcamera/control_ids.h> + +#include <libcamera/ipa/core_ipa_interface.h> + +#include "libipa/colours.h" +#include "libipa/histogram.h" + +/** + * \file agc.h + */ + +namespace libcamera { + +using namespace std::literals::chrono_literals; + +namespace ipa::ipu3::algorithms { + +/** + * \class Agc + * \brief A mean-based auto-exposure algorithm + * + * This algorithm calculates an exposure time and an analogue gain so that the + * average value of the green channel of the brightest 2% of pixels approaches + * 0.5. The AWB gains are not used here, and all cells in the grid have the same + * weight, like an average-metering case. In this metering mode, the camera uses + * light information from the entire scene and creates an average for the final + * exposure setting, giving no weighting to any particular portion of the + * metered area. + * + * Reference: Battiato, Messina & Castorina. (2008). Exposure + * Correction for Imaging Devices: An Overview. 10.1201/9781420054538.ch12. + */ + +LOG_DEFINE_CATEGORY(IPU3Agc) + +/* Minimum limit for analogue gain value */ +static constexpr double kMinAnalogueGain = 1.0; + +/* \todo Honour the FrameDurationLimits control instead of hardcoding a limit */ +static constexpr utils::Duration kMaxExposureTime = 60ms; + +/* Histogram constants */ +static constexpr uint32_t knumHistogramBins = 256; + +Agc::Agc() + : minExposureTime_(0s), maxExposureTime_(0s) +{ +} + +/** + * \brief Initialise the AGC algorithm from tuning files + * \param[in] context The shared IPA context + * \param[in] tuningData The YamlObject containing Agc tuning data + * + * This function calls the base class' tuningData parsers to discover which + * control values are supported. + * + * \return 0 on success or errors from the base class + */ +int Agc::init(IPAContext &context, const YamlObject &tuningData) +{ + int ret; + + ret = parseTuningData(tuningData); + if (ret) + return ret; + + context.ctrlMap.merge(controls()); + + return 0; +} + +/** + * \brief Configure the AGC given a configInfo + * \param[in] context The shared IPA context + * \param[in] configInfo The IPA configuration data + * + * \return 0 + */ +int Agc::configure(IPAContext &context, + [[maybe_unused]] const IPAConfigInfo &configInfo) +{ + const IPASessionConfiguration &configuration = context.configuration; + IPAActiveState &activeState = context.activeState; + + stride_ = configuration.grid.stride; + bdsGrid_ = configuration.grid.bdsGrid; + + minExposureTime_ = configuration.agc.minExposureTime; + maxExposureTime_ = std::min(configuration.agc.maxExposureTime, + kMaxExposureTime); + + minAnalogueGain_ = std::max(configuration.agc.minAnalogueGain, kMinAnalogueGain); + maxAnalogueGain_ = configuration.agc.maxAnalogueGain; + + /* Configure the default exposure and gain. */ + activeState.agc.gain = minAnalogueGain_; + activeState.agc.exposure = 10ms / configuration.sensor.lineDuration; + + context.activeState.agc.constraintMode = constraintModes().begin()->first; + context.activeState.agc.exposureMode = exposureModeHelpers().begin()->first; + + /* \todo Run this again when FrameDurationLimits is passed in */ + setLimits(minExposureTime_, maxExposureTime_, minAnalogueGain_, + maxAnalogueGain_); + resetFrameCount(); + + return 0; +} + +Histogram Agc::parseStatistics(const ipu3_uapi_stats_3a *stats, + const ipu3_uapi_grid_config &grid) +{ + uint32_t hist[knumHistogramBins] = { 0 }; + + rgbTriples_.clear(); + + for (unsigned int cellY = 0; cellY < grid.height; cellY++) { + for (unsigned int cellX = 0; cellX < grid.width; cellX++) { + uint32_t cellPosition = cellY * stride_ + cellX; + + const ipu3_uapi_awb_set_item *cell = + reinterpret_cast<const ipu3_uapi_awb_set_item *>( + &stats->awb_raw_buffer.meta_data[cellPosition]); + + rgbTriples_.push_back({ + cell->R_avg, + (cell->Gr_avg + cell->Gb_avg) / 2, + cell->B_avg + }); + + /* + * Store the average green value to estimate the + * brightness. Even the overexposed pixels are + * taken into account. + */ + hist[(cell->Gr_avg + cell->Gb_avg) / 2]++; + } + } + + return Histogram(Span<uint32_t>(hist)); +} + +/** + * \brief Estimate the relative luminance of the frame with a given gain + * \param[in] gain The gain to apply in estimating luminance + * + * The estimation is based on the AWB statistics for the current frame. Red, + * green and blue averages for all cells are first multiplied by the gain, and + * then saturated to approximate the sensor behaviour at high brightness + * values. The approximation is quite rough, as it doesn't take into account + * non-linearities when approaching saturation. + * + * The relative luminance (Y) is computed from the linear RGB components using + * the Rec. 601 formula. The values are normalized to the [0.0, 1.0] range, + * where 1.0 corresponds to a theoretical perfect reflector of 100% reference + * white. + * + * More detailed information can be found in: + * https://en.wikipedia.org/wiki/Relative_luminance + * + * \return The relative luminance of the frame + */ +double Agc::estimateLuminance(double gain) const +{ + RGB<double> sum{ 0.0 }; + + for (unsigned int i = 0; i < rgbTriples_.size(); i++) { + sum.r() += std::min(std::get<0>(rgbTriples_[i]) * gain, 255.0); + sum.g() += std::min(std::get<1>(rgbTriples_[i]) * gain, 255.0); + sum.b() += std::min(std::get<2>(rgbTriples_[i]) * gain, 255.0); + } + + RGB<double> gains{{ rGain_, gGain_, bGain_ }}; + double ySum = rec601LuminanceFromRGB(sum * gains); + return ySum / (bdsGrid_.height * bdsGrid_.width) / 255; +} + +/** + * \brief Process IPU3 statistics, and run AGC operations + * \param[in] context The shared IPA context + * \param[in] frame The current frame sequence number + * \param[in] frameContext The current frame context + * \param[in] stats The IPU3 statistics and ISP results + * \param[out] metadata Metadata for the frame, to be filled by the algorithm + * + * Identify the current image brightness, and use that to estimate the optimal + * new exposure and gain for the scene. + */ +void Agc::process(IPAContext &context, [[maybe_unused]] const uint32_t frame, + IPAFrameContext &frameContext, + const ipu3_uapi_stats_3a *stats, + ControlList &metadata) +{ + Histogram hist = parseStatistics(stats, context.configuration.grid.bdsGrid); + rGain_ = context.activeState.awb.gains.red; + gGain_ = context.activeState.awb.gains.blue; + bGain_ = context.activeState.awb.gains.green; + + /* + * The Agc algorithm needs to know the effective exposure value that was + * applied to the sensor when the statistics were collected. + */ + utils::Duration exposureTime = context.configuration.sensor.lineDuration + * frameContext.sensor.exposure; + double analogueGain = frameContext.sensor.gain; + utils::Duration effectiveExposureValue = exposureTime * analogueGain; + + utils::Duration newExposureTime; + double aGain, dGain; + std::tie(newExposureTime, aGain, dGain) = + calculateNewEv(context.activeState.agc.constraintMode, + context.activeState.agc.exposureMode, hist, + effectiveExposureValue); + + LOG(IPU3Agc, Debug) + << "Divided up exposure time, analogue gain and digital gain are " + << newExposureTime << ", " << aGain << " and " << dGain; + + IPAActiveState &activeState = context.activeState; + /* Update the estimated exposure time and gain. */ + activeState.agc.exposure = newExposureTime / context.configuration.sensor.lineDuration; + activeState.agc.gain = aGain; + + metadata.set(controls::AnalogueGain, frameContext.sensor.gain); + metadata.set(controls::ExposureTime, exposureTime.get<std::micro>()); + + /* \todo Use VBlank value calculated from each frame exposure. */ + uint32_t vTotal = context.configuration.sensor.size.height + + context.configuration.sensor.defVBlank; + utils::Duration frameDuration = context.configuration.sensor.lineDuration + * vTotal; + metadata.set(controls::FrameDuration, frameDuration.get<std::micro>()); +} + +REGISTER_IPA_ALGORITHM(Agc, "Agc") + +} /* namespace ipa::ipu3::algorithms */ + +} /* namespace libcamera */ |