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/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
* Copyright (C) 2021, Ideas On Board
*
* ipu3_agc.cpp - AGC/AEC control algorithm
*/
#include "agc.h"
#include <algorithm>
#include <chrono>
#include <cmath>
#include <libcamera/base/log.h>
#include <libcamera/ipa/core_ipa_interface.h>
#include "libipa/histogram.h"
namespace libcamera {
using namespace std::literals::chrono_literals;
namespace ipa::ipu3::algorithms {
LOG_DEFINE_CATEGORY(IPU3Agc)
/* Number of frames to wait before calculating stats on minimum exposure */
static constexpr uint32_t kInitialFrameMinAECount = 4;
/* Number of frames to wait between new gain/exposure estimations */
static constexpr uint32_t kFrameSkipCount = 6;
/* Maximum ISO value for analogue gain */
static constexpr uint32_t kMinISO = 100;
static constexpr uint32_t kMaxISO = 1500;
/* Maximum analogue gain value
* \todo grab it from a camera helper */
static constexpr uint32_t kMinGain = kMinISO / 100;
static constexpr uint32_t kMaxGain = kMaxISO / 100;
/* \todo use calculated value based on sensor */
static constexpr uint32_t kMinExposure = 1;
static constexpr uint32_t kMaxExposure = 1976;
/* Histogram constants */
static constexpr uint32_t knumHistogramBins = 256;
static constexpr double kEvGainTarget = 0.5;
Agc::Agc()
: frameCount_(0), lastFrame_(0), iqMean_(0.0), lineDuration_(0s),
maxExposureTime_(0s), prevExposure_(0s), prevExposureNoDg_(0s),
currentExposure_(0s), currentExposureNoDg_(0s)
{
}
int Agc::configure(IPAContext &context, const IPAConfigInfo &configInfo)
{
stride_ = context.configuration.grid.stride;
lineDuration_ = configInfo.sensorInfo.lineLength * 1.0s
/ configInfo.sensorInfo.pixelRate;
maxExposureTime_ = kMaxExposure * lineDuration_;
return 0;
}
void Agc::processBrightness(const ipu3_uapi_stats_3a *stats,
const ipu3_uapi_grid_config &grid)
{
uint32_t hist[knumHistogramBins] = { 0 };
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]
);
if (cell->sat_ratio == 0) {
uint8_t gr = cell->Gr_avg;
uint8_t gb = cell->Gb_avg;
hist[(gr + gb) / 2]++;
}
}
}
/* Estimate the quantile mean of the top 2% of the histogram */
iqMean_ = Histogram(Span<uint32_t>(hist)).interQuantileMean(0.98, 1.0);
}
void Agc::filterExposure()
{
double speed = 0.2;
if (prevExposure_ == 0s) {
/* DG stands for digital gain.*/
prevExposure_ = currentExposure_;
prevExposureNoDg_ = currentExposureNoDg_;
} else {
/*
* If we are close to the desired result, go faster to avoid making
* multiple micro-adjustments.
* \ todo: Make this customisable?
*/
if (prevExposure_ < 1.2 * currentExposure_ &&
prevExposure_ > 0.8 * currentExposure_)
speed = sqrt(speed);
prevExposure_ = speed * currentExposure_ +
prevExposure_ * (1.0 - speed);
prevExposureNoDg_ = speed * currentExposureNoDg_ +
prevExposureNoDg_ * (1.0 - speed);
}
/*
* We can't let the no_dg exposure deviate too far below the
* total exposure, as there might not be enough digital gain available
* in the ISP to hide it (which will cause nasty oscillation).
*/
double fastReduceThreshold = 0.4;
if (prevExposureNoDg_ <
prevExposure_ * fastReduceThreshold)
prevExposureNoDg_ = prevExposure_ * fastReduceThreshold;
LOG(IPU3Agc, Debug) << "After filtering, total_exposure " << prevExposure_;
}
void Agc::lockExposureGain(uint32_t &exposure, double &gain)
{
/* Algorithm initialization should wait for first valid frames */
/* \todo - have a number of frames given by DelayedControls ?
* - implement a function for IIR */
if ((frameCount_ < kInitialFrameMinAECount) || (frameCount_ - lastFrame_ < kFrameSkipCount))
return;
/* Are we correctly exposed ? */
if (std::abs(iqMean_ - kEvGainTarget * knumHistogramBins) <= 1) {
LOG(IPU3Agc, Debug) << "!!! Good exposure with iqMean = " << iqMean_;
} else {
double newGain = kEvGainTarget * knumHistogramBins / iqMean_;
/* extracted from Rpi::Agc::computeTargetExposure */
utils::Duration currentShutter = exposure * lineDuration_;
currentExposureNoDg_ = currentShutter * gain;
LOG(IPU3Agc, Debug) << "Actual total exposure " << currentExposureNoDg_
<< " Shutter speed " << currentShutter
<< " Gain " << gain;
currentExposure_ = currentExposureNoDg_ * newGain;
utils::Duration maxTotalExposure = maxExposureTime_ * kMaxGain;
currentExposure_ = std::min(currentExposure_, maxTotalExposure);
LOG(IPU3Agc, Debug) << "Target total exposure " << currentExposure_;
/* \todo: estimate if we need to desaturate */
filterExposure();
utils::Duration newExposure = 0.0s;
if (currentShutter < maxExposureTime_) {
exposure = std::clamp(static_cast<uint32_t>(exposure * currentExposure_ / currentExposureNoDg_), kMinExposure, kMaxExposure);
newExposure = currentExposure_ / exposure;
gain = std::clamp(static_cast<uint32_t>(gain * currentExposure_ / newExposure), kMinGain, kMaxGain);
} else if (currentShutter >= maxExposureTime_) {
gain = std::clamp(static_cast<uint32_t>(gain * currentExposure_ / currentExposureNoDg_), kMinGain, kMaxGain);
newExposure = currentExposure_ / gain;
exposure = std::clamp(static_cast<uint32_t>(exposure * currentExposure_ / newExposure), kMinExposure, kMaxExposure);
}
LOG(IPU3Agc, Debug) << "Adjust exposure " << exposure * lineDuration_ << " and gain " << gain;
}
lastFrame_ = frameCount_;
}
void Agc::process(IPAContext &context, const ipu3_uapi_stats_3a *stats)
{
uint32_t &exposure = context.frameContext.agc.exposure;
double &gain = context.frameContext.agc.gain;
processBrightness(stats, context.configuration.grid.bdsGrid);
lockExposureGain(exposure, gain);
frameCount_++;
}
} /* namespace ipa::ipu3::algorithms */
} /* namespace libcamera */
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