[libcamera-devel] [PATCH v3 09/11] ipa: rkisp1: Introduce AGC
Kieran Bingham
kieran.bingham at ideasonboard.com
Tue Nov 23 17:08:49 CET 2021
Hi JM,
Some question inline ...
Quoting Jean-Michel Hautbois (2021-11-23 15:04:21)
> Now that we have IPAContext and Algorithm, we can implement a simple AGC
> based on the IPU3 one. It is very similar, except that there is no
> histogram used for an inter quantile mean. The RkISP1 is returning a 5x5
> array (for V10) of luminance means. Estimating the relative luminance is
> thus a simple mean of all the blocks already calculated by the ISP.
>
> Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois at ideasonboard.com>
> ---
> src/ipa/rkisp1/algorithms/agc.cpp | 265 ++++++++++++++++++++++++++
> src/ipa/rkisp1/algorithms/agc.h | 55 ++++++
> src/ipa/rkisp1/algorithms/meson.build | 1 +
> src/ipa/rkisp1/ipa_context.cpp | 44 +++++
> src/ipa/rkisp1/ipa_context.h | 17 ++
> src/ipa/rkisp1/rkisp1.cpp | 72 +++----
> 6 files changed, 419 insertions(+), 35 deletions(-)
> create mode 100644 src/ipa/rkisp1/algorithms/agc.cpp
> create mode 100644 src/ipa/rkisp1/algorithms/agc.h
>
> diff --git a/src/ipa/rkisp1/algorithms/agc.cpp b/src/ipa/rkisp1/algorithms/agc.cpp
> new file mode 100644
> index 00000000..9c6d312e
> --- /dev/null
> +++ b/src/ipa/rkisp1/algorithms/agc.cpp
> @@ -0,0 +1,265 @@
> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> +/*
> + * Copyright (C) 2021, Ideas On Board
> + *
> + * agc.cpp - AGC/AEC mean-based control algorithm
> + */
> +
> +#include "agc.h"
> +
> +#include <algorithm>
> +#include <chrono>
> +#include <cmath>
> +
> +#include <libcamera/base/log.h>
> +
> +#include <libcamera/ipa/core_ipa_interface.h>
> +
> +/**
> + * \file agc.h
> + */
> +
> +namespace libcamera {
> +
> +using namespace std::literals::chrono_literals;
> +
> +namespace ipa::rkisp1::algorithms {
> +
> +/**
> + * \class Agc
> + * \brief A mean-based auto-exposure algorithm
> + */
> +
> +LOG_DEFINE_CATEGORY(RkISP1Agc)
> +
> +/* Limits for analogue gain values */
> +static constexpr double kMinAnalogueGain = 1.0;
> +static constexpr double kMaxAnalogueGain = 8.0;
> +
> +/* \todo Honour the FrameDurationLimits control instead of hardcoding a limit */
> +static constexpr utils::Duration kMaxShutterSpeed = 60ms;
> +
> +/* Number of frames to wait before calculating stats on minimum exposure */
> +static constexpr uint32_t kNumStartupFrames = 10;
> +
> +/*
> + * Relative luminance target.
> + *
> + * It's a number that's chosen so that, when the camera points at a grey
> + * target, the resulting image brightness is considered right.
> + */
> +static constexpr double kRelativeLuminanceTarget = 0.4;
> +
> +Agc::Agc()
> + : frameCount_(0), lineDuration_(0s), minShutterSpeed_(0s),
> + maxShutterSpeed_(0s), filteredExposure_(0s), currentExposure_(0s)
> +{
> +}
> +
> +/**
> + * \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, const IPACameraSensorInfo &configInfo)
> +{
> + /* \todo use the IPAContext to provide the limits */
> + lineDuration_ = configInfo.lineLength * 1.0s / configInfo.pixelRate;
> +
> + minShutterSpeed_ = context.configuration.agc.minShutterSpeed;
> + maxShutterSpeed_ = std::min(context.configuration.agc.maxShutterSpeed,
> + kMaxShutterSpeed);
> +
> + minAnalogueGain_ = std::max(context.configuration.agc.minAnalogueGain, kMinAnalogueGain);
> + maxAnalogueGain_ = std::min(context.configuration.agc.maxAnalogueGain, kMaxAnalogueGain);
> +
> + /* Configure the default exposure and gain. */
> + context.frameContext.agc.gain = minAnalogueGain_;
> + context.frameContext.agc.exposure = 10ms / lineDuration_;
> +
> + return 0;
> +}
> +
> +/**
> + * \brief Apply a filter on the exposure value to limit the speed of changes
> + */
> +void Agc::filterExposure()
> +{
> + double speed = 0.2;
> +
> + /* Adapt instantly if we are in startup phase */
> + if (frameCount_ < kNumStartupFrames)
> + speed = 1.0;
> +
> + if (filteredExposure_ == 0s) {
> + /* DG stands for digital gain.*/
I think that comment is now stale.
If it's stale in the IPU3 as well, can you remove it there too please?
> + filteredExposure_ = currentExposure_;
> + } else {
> + /*
> + * If we are close to the desired result, go faster to avoid making
faster ? or slower?
Oh - ok this checks out ;-) I almost got caught out forgetting that the
square root of a number less than one - increases towards one ;=)
> + * multiple micro-adjustments.
> + * \todo Make this customisable?
> + */
> + if (filteredExposure_ < 1.2 * currentExposure_ &&
> + filteredExposure_ > 0.8 * currentExposure_)
> + speed = sqrt(speed);
> +
> + filteredExposure_ = speed * currentExposure_ +
> + filteredExposure_ * (1.0 - speed);
> + }
> +
> + LOG(RkISP1Agc, Debug) << "After filtering, total_exposure " << filteredExposure_;
> +}
> +
> +/**
> + * \brief Estimate the new exposure and gain values
> + * \param[inout] frameContext The shared IPA frame Context
> + * \param[in] yGain The gain calculated on the current brightness level
> + */
> +void Agc::computeExposure(IPAFrameContext &frameContext, double yGain)
> +{
> + /* Get the effective exposure and gain applied on the sensor. */
> + uint32_t exposure = frameContext.sensor.exposure;
> + double analogueGain = frameContext.sensor.gain;
> +
> + /* Consider within 1% of the target as correctly exposed */
> + if (std::abs(yGain - 1.0) < 0.01)
> + LOG(RkISP1Agc, Debug) << "We are well exposed (iqMean = "
> + << yGain << ")";
> +
> + /* extracted from Rpi::Agc::computeTargetExposure */
> +
> + /* Calculate the shutter time in seconds */
> + utils::Duration currentShutter = exposure * lineDuration_;
> +
> + /*
> + * Update the exposure value for the next computation using the values
> + * of exposure and gain really used by the sensor.
> + */
> + utils::Duration effectiveExposureValue = currentShutter * analogueGain;
> +
> + LOG(RkISP1Agc, Debug) << "Actual total exposure " << currentShutter * analogueGain
> + << " Shutter speed " << currentShutter
> + << " Gain " << analogueGain
> + << " Needed ev gain " << yGain;
> +
> + /*
> + * Calculate the current exposure value for the scene as the latest
> + * exposure value applied multiplied by the new estimated gain.
> + */
> + currentExposure_ = effectiveExposureValue * yGain;
> +
> + /* Clamp the exposure value to the min and max authorized */
> + utils::Duration maxTotalExposure = maxShutterSpeed_ * maxAnalogueGain_;
> + currentExposure_ = std::min(currentExposure_, maxTotalExposure);
> + LOG(RkISP1Agc, Debug) << "Target total exposure " << currentExposure_
> + << ", maximum is " << maxTotalExposure;
> +
> + /* \todo: estimate if we need to desaturate */
> + filterExposure();
Would returning the filtedExposure value from the function make it
clearer or more explicit than it gets used ?
> +
> + /* Divide the exposure value as new exposure and gain values */
> + utils::Duration exposureValue = filteredExposure_;
i.e.
utils::Duration exposureValue = filteredExposure();
?
> + utils::Duration shutterTime;
> +
> + /*
> + * Push the shutter time up to the maximum first, and only then
> + * increase the gain.
> + */
> + shutterTime = std::clamp<utils::Duration>(exposureValue / minAnalogueGain_,
> + minShutterSpeed_, maxShutterSpeed_);
> + double stepGain = std::clamp(exposureValue / shutterTime,
> + minAnalogueGain_, maxAnalogueGain_);
> + LOG(RkISP1Agc, Debug) << "Divided up shutter and gain are "
> + << shutterTime << " and "
> + << stepGain;
> +
> + /* Update the estimated exposure and gain. */
> + frameContext.agc.exposure = shutterTime / lineDuration_;
> + frameContext.agc.gain = stepGain;
> +}
> +
> +/**
> + * \brief Estimate the relative luminance of the frame with a given gain
> + * \param[in] ae The RkISP1 statistics and ISP results
> + * \param[in] gain The gain calculated on the current brightness level
> + * \return The relative luminance
> + *
> + * This function estimates the average relative luminance of the frame that
> + * would be output by the sensor if an additional \a gain was applied.
> + *
> + * The estimation is based on the AE statistics for the current frame. Y
> + * 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 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
> + */
> +double Agc::estimateLuminance(const rkisp1_cif_isp_ae_stat *ae,
> + double gain)
> +{
> + double ySum = 0.0;
> + unsigned int num = 0;
> +
> + /* Sum the averages, saturated to 255. */
> + for (unsigned int aeCell = 0; aeCell < numCells_; aeCell++) {
> + ySum += std::min(ae->exp_mean[aeCell] * gain, 255.0);
> + num++;
> + }
> +
> + /* \todo Weight with the AWB gains */
> +
> + return ySum / num / 255;
> +}
> +
> +/**
> + * \brief Process RkISP1 statistics, and run AGC operations
> + * \param[in] context The shared IPA context
> + * \param[in] stats The RKIsp1 statistics and ISP results
> + *
> + * Identify the current image brightness, and use that to estimate the optimal
> + * new exposure and gain for the scene.
> + */
> +void Agc::process(IPAContext &context, const rkisp1_stat_buffer *stats)
> +{
> + const rkisp1_cif_isp_stat *params = &stats->params;
> + ASSERT(stats->meas_type & RKISP1_CIF_ISP_STAT_AUTOEXP);
> +
> + const rkisp1_cif_isp_ae_stat *ae = ¶ms->ae;
> +
> + /*
> + * Estimate the gain needed to achieve a relative luminance target. 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.
> + */
> + double yGain = 1.0;
> + double yTarget = kRelativeLuminanceTarget;
> +
> + for (unsigned int i = 0; i < 8; i++) {
> + double yValue = estimateLuminance(ae, yGain);
> + double extra_gain = std::min(10.0, yTarget / (yValue + .001));
> +
> + yGain *= extra_gain;
> + LOG(RkISP1Agc, Debug) << "Y value: " << yValue
> + << ", Y target: " << yTarget
> + << ", gives gain " << yGain;
> + if (extra_gain < 1.01)
> + break;
> + }
> +
> + computeExposure(context.frameContext, yGain);
Does the algorithm need to track the frameCount internally? Can it get
it from the frame / index of the request / stats?
> + frameCount_++;
> +}
> +
> +} /* namespace ipa::rkisp1::algorithms */
> +
> +} /* namespace libcamera */
> diff --git a/src/ipa/rkisp1/algorithms/agc.h b/src/ipa/rkisp1/algorithms/agc.h
> new file mode 100644
> index 00000000..83159743
> --- /dev/null
> +++ b/src/ipa/rkisp1/algorithms/agc.h
> @@ -0,0 +1,55 @@
> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> +/*
> + * Copyright (C) 2021, Ideas On Board
> + *
> + * agc.h - RkISP1 AGC/AEC mean-based control algorithm
> + */
> +#ifndef __LIBCAMERA_RKISP1_ALGORITHMS_AGC_H__
> +#define __LIBCAMERA_RKISP1_ALGORITHMS_AGC_H__
> +
> +#include <linux/rkisp1-config.h>
> +
> +#include <libcamera/base/utils.h>
> +
> +#include <libcamera/geometry.h>
> +
> +#include "algorithm.h"
> +
> +namespace libcamera {
> +
> +struct IPACameraSensorInfo;
> +
> +namespace ipa::rkisp1::algorithms {
> +
> +class Agc : public Algorithm
> +{
> +public:
> + Agc();
> + ~Agc() = default;
> +
> + int configure(IPAContext &context, const IPACameraSensorInfo &configInfo) override;
> + void process(IPAContext &context, const rkisp1_stat_buffer *stats) override;
> +
> +private:
> + void filterExposure();
> + void computeExposure(IPAFrameContext &frameContext, double yGain);
> + double estimateLuminance(const rkisp1_cif_isp_ae_stat *ae, double gain);
> +
> + uint64_t frameCount_;
> +
> + utils::Duration lineDuration_;
> + utils::Duration minShutterSpeed_;
> + utils::Duration maxShutterSpeed_;
> +
> + double minAnalogueGain_;
> + double maxAnalogueGain_;
Do all these need to be duplicated from the context? Can't we use the
values from the IPASessionConfiguration?
> +
> + utils::Duration filteredExposure_;
> + utils::Duration currentExposure_;
> +};
> +
> +} /* namespace ipa::rkisp1::algorithms */
> +
> +} /* namespace libcamera */
> +
> +#endif /* __LIBCAMERA_RKISP1_ALGORITHMS_AGC_H__ */
> diff --git a/src/ipa/rkisp1/algorithms/meson.build b/src/ipa/rkisp1/algorithms/meson.build
> index 1c6c59cf..a19c1a4f 100644
> --- a/src/ipa/rkisp1/algorithms/meson.build
> +++ b/src/ipa/rkisp1/algorithms/meson.build
> @@ -1,4 +1,5 @@
> # SPDX-License-Identifier: CC0-1.0
>
> rkisp1_ipa_algorithms = files([
> + 'agc.cpp',
> ])
> diff --git a/src/ipa/rkisp1/ipa_context.cpp b/src/ipa/rkisp1/ipa_context.cpp
> index 819b2c73..16fc248f 100644
> --- a/src/ipa/rkisp1/ipa_context.cpp
> +++ b/src/ipa/rkisp1/ipa_context.cpp
> @@ -55,4 +55,48 @@ namespace libcamera::ipa::rkisp1 {
> * are run. This needs to be turned into real per-frame data storage.
> */
>
> +/**
> + * \var IPASessionConfiguration::agc
> + * \brief AGC parameters configuration of the IPA
> + *
> + * \var IPASessionConfiguration::agc.minShutterSpeed
> + * \brief Minimum shutter speed supported with the configured sensor
> + *
> + * \var IPASessionConfiguration::agc.maxShutterSpeed
> + * \brief Maximum shutter speed supported with the configured sensor
> + *
> + * \var IPASessionConfiguration::agc.minAnalogueGain
> + * \brief Minimum analogue gain supported with the configured sensor
> + *
> + * \var IPASessionConfiguration::agc.maxAnalogueGain
> + * \brief Maximum analogue gain supported with the configured sensor
> + */
> +
> +/**
> + * \var IPAFrameContext::agc
> + * \brief Context for the Automatic Gain Control algorithm
> + *
> + * The exposure and gain determined are expected to be applied to the sensor
> + * at the earliest opportunity.
> + *
> + * \var IPAFrameContext::agc.exposure
> + * \brief Exposure time expressed as a number of lines
> + *
> + * \var IPAFrameContext::agc.gain
> + * \brief Analogue gain multiplier
> + *
> + * The gain should be adapted to the sensor specific gain code before applying.
> + */
> +
> +/**
> + * \var IPAFrameContext::sensor
> + * \brief Effective sensor values
> + *
> + * \var IPAFrameContext::sensor.exposure
> + * \brief Exposure time expressed as a number of lines
> + *
> + * \var IPAFrameContext::sensor.gain
> + * \brief Analogue gain multiplier
> + */
> +
> } /* namespace libcamera::ipa::rkisp1 */
> diff --git a/src/ipa/rkisp1/ipa_context.h b/src/ipa/rkisp1/ipa_context.h
> index ff40efe3..8e756fb1 100644
> --- a/src/ipa/rkisp1/ipa_context.h
> +++ b/src/ipa/rkisp1/ipa_context.h
> @@ -8,14 +8,31 @@
> #ifndef __LIBCAMERA_RKISP1_IPA_CONTEXT_H__
> #define __LIBCAMERA_RKISP1_IPA_CONTEXT_H__
>
> +#include <libcamera/base/utils.h>
> +
> namespace libcamera {
>
> namespace ipa::rkisp1 {
>
> struct IPASessionConfiguration {
> + struct {
> + utils::Duration minShutterSpeed;
> + utils::Duration maxShutterSpeed;
> + double minAnalogueGain;
> + double maxAnalogueGain;
> + } agc;
> };
>
> struct IPAFrameContext {
> + struct {
> + uint32_t exposure;
> + double gain;
> + } agc;
> +
> + struct {
> + uint32_t exposure;
> + double gain;
> + } sensor;
> };
>
> struct IPAContext {
> diff --git a/src/ipa/rkisp1/rkisp1.cpp b/src/ipa/rkisp1/rkisp1.cpp
> index b5aa93f8..89d98b6c 100644
> --- a/src/ipa/rkisp1/rkisp1.cpp
> +++ b/src/ipa/rkisp1/rkisp1.cpp
> @@ -25,6 +25,7 @@
>
> #include <libcamera/internal/mapped_framebuffer.h>
>
> +#include "algorithms/agc.h"
> #include "algorithms/algorithm.h"
> #include "libipa/camera_sensor_helper.h"
>
> @@ -32,6 +33,8 @@ namespace libcamera {
>
> LOG_DEFINE_CATEGORY(IPARkISP1)
>
> +using namespace std::literals::chrono_literals;
> +
> namespace ipa::rkisp1 {
>
> class IPARkISP1 : public IPARkISP1Interface
> @@ -77,6 +80,8 @@ private:
> unsigned int hwGammaOutMaxSamples_;
> unsigned int hwHistogramWeightGridsSize_;
>
> + utils::Duration lineDuration_;
> +
Does this need to be stored privately? or can it be stored in the
Context?
Or rather, does this get used by the algorithms directly? If not - then
it's fine here.
> /* Interface to the Camera Helper */
> std::unique_ptr<CameraSensorHelper> camHelper_;
>
> @@ -120,6 +125,9 @@ int IPARkISP1::init(const IPASettings &settings, unsigned int hwRevision)
> return -ENODEV;
> }
>
> + /* Construct our Algorithms */
> + algorithms_.push_back(std::make_unique<algorithms::Agc>());
> +
> return 0;
> }
>
> @@ -171,9 +179,29 @@ int IPARkISP1::configure([[maybe_unused]] const IPACameraSensorInfo &info,
> << "Exposure: " << minExposure_ << "-" << maxExposure_
> << " Gain: " << minGain_ << "-" << maxGain_;
>
> + lineDuration_ = info.lineLength * 1.0s / info.pixelRate;
> +
> /* Clean context at configuration */
> context_ = {};
>
> + /*
> + * When the AGC computes the new exposure values for a frame, it needs
> + * to know the limits for shutter speed and analogue gain.
> + * As it depends on the sensor, update it with the controls.
> + *
> + * \todo take VBLANK into account for maximum shutter speed
> + */
> + context_.configuration.agc.minShutterSpeed = minExposure_ * lineDuration_;
> + context_.configuration.agc.maxShutterSpeed = maxExposure_ * lineDuration_;
> + context_.configuration.agc.minAnalogueGain = camHelper_->gain(minGain_);
> + context_.configuration.agc.maxAnalogueGain = camHelper_->gain(maxGain_);
> +
> + for (auto const &algo : algorithms_) {
> + int ret = algo->configure(context_, info);
> + if (ret)
> + return ret;
> + }
> +
> return 0;
> }
>
> @@ -218,6 +246,9 @@ void IPARkISP1::processEvent(const RkISP1Event &event)
> reinterpret_cast<rkisp1_stat_buffer *>(
> mappedBuffers_.at(bufferId).planes()[0].data());
>
> + context_.frameContext.sensor.exposure = event.sensorControls.get(V4L2_CID_EXPOSURE).get<int32_t>();
> + context_.frameContext.sensor.gain = camHelper_->gain(event.sensorControls.get(V4L2_CID_ANALOGUE_GAIN).get<int32_t>());
> +
> updateStatistics(frame, stats);
> break;
> }
> @@ -262,44 +293,12 @@ void IPARkISP1::queueRequest(unsigned int frame, rkisp1_params_cfg *params,
> void IPARkISP1::updateStatistics(unsigned int frame,
> const rkisp1_stat_buffer *stats)
> {
> - const rkisp1_cif_isp_stat *params = &stats->params;
> unsigned int aeState = 0;
>
> - if (stats->meas_type & RKISP1_CIF_ISP_STAT_AUTOEXP) {
> - const rkisp1_cif_isp_ae_stat *ae = ¶ms->ae;
> -
> - const unsigned int target = 60;
> + for (auto const &algo : algorithms_)
> + algo->process(context_, stats);
>
> - unsigned int value = 0;
> - unsigned int num = 0;
> - for (unsigned int i = 0; i < hwAeMeanMax_; i++) {
> - if (ae->exp_mean[i] <= 15)
> - continue;
> -
> - value += ae->exp_mean[i];
> - num++;
> - }
> - value /= num;
> -
> - double factor = (double)target / value;
> -
> - if (frame % 3 == 0) {
> - double exposure;
> -
> - exposure = factor * exposure_ * gain_ / minGain_;
> - exposure_ = std::clamp<uint64_t>((uint64_t)exposure,
> - minExposure_,
> - maxExposure_);
> -
> - exposure = exposure / exposure_ * minGain_;
> - gain_ = std::clamp<uint64_t>((uint64_t)exposure,
> - minGain_, maxGain_);
> -
> - setControls(frame + 1);
> - }
> -
> - aeState = fabs(factor - 1.0f) < 0.05f ? 2 : 1;
> - }
> + setControls(frame + 1);
Is + 1 the correct target frame?
Is that always true even if there are multiple frames queued?
>
> metadataReady(frame, aeState);
> }
> @@ -309,6 +308,9 @@ void IPARkISP1::setControls(unsigned int frame)
> RkISP1Action op;
> op.op = ActionV4L2Set;
>
> + exposure_ = context_.frameContext.agc.exposure;
> + gain_ = camHelper_->gainCode(context_.frameContext.agc.gain);
> +
> ControlList ctrls(ctrls_);
> ctrls.set(V4L2_CID_EXPOSURE, static_cast<int32_t>(exposure_));
> ctrls.set(V4L2_CID_ANALOGUE_GAIN, static_cast<int32_t>(gain_));
> --
> 2.32.0
>
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