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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 "ipu3_agc.h"
#include <algorithm>
#include <cmath>
#include <numeric>
#include <libcamera/ipa/core_ipa_interface.h>
#include "libcamera/internal/log.h"
#include "libipa/histogram.h"
namespace libcamera {
namespace ipa::ipu3 {
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;
/* A cell is 8 bytes and contains averages for RGB values and saturation ratio */
static constexpr uint8_t kCellSize = 8;
IPU3Agc::IPU3Agc()
: frameCount_(0), lastFrame_(0), converged_(false),
updateControls_(false), iqMean_(0.0), gamma_(1.0),
lineDuration_(0.0), maxExposureTime_(0.0),
prevExposure_(0.0), prevExposureNoDg_(0.0),
currentExposure_(0.0), currentExposureNoDg_(0.0)
{
}
void IPU3Agc::initialise(struct ipu3_uapi_grid_config &bdsGrid, const IPACameraSensorInfo &sensorInfo)
{
aeGrid_ = bdsGrid;
/* line duration in microseconds */
lineDuration_ = sensorInfo.lineLength * 1000000ULL / static_cast<double>(sensorInfo.pixelRate);
maxExposureTime_ = kMaxExposure * lineDuration_;
}
void IPU3Agc::processBrightness(const ipu3_uapi_stats_3a *stats)
{
const struct ipu3_uapi_grid_config statsAeGrid = stats->stats_4a_config.awb_config.grid;
Rectangle aeRegion = { statsAeGrid.x_start,
statsAeGrid.y_start,
static_cast<unsigned int>(statsAeGrid.x_end - statsAeGrid.x_start) + 1,
static_cast<unsigned int>(statsAeGrid.y_end - statsAeGrid.y_start) + 1 };
Point topleft = aeRegion.topLeft();
int topleftX = topleft.x >> aeGrid_.block_width_log2;
int topleftY = topleft.y >> aeGrid_.block_height_log2;
/* Align to the grid cell width and height */
uint32_t startX = topleftX << aeGrid_.block_width_log2;
uint32_t startY = topleftY * aeGrid_.width << aeGrid_.block_width_log2;
uint32_t endX = (startX + (aeRegion.size().width >> aeGrid_.block_width_log2)) << aeGrid_.block_width_log2;
uint32_t i, j;
uint32_t count = 0;
uint32_t hist[knumHistogramBins] = { 0 };
for (j = topleftY;
j < topleftY + (aeRegion.size().height >> aeGrid_.block_height_log2);
j++) {
for (i = startX + startY; i < endX + startY; i += kCellSize) {
/*
* The grid width (and maybe height) is not reliable.
* We observed a bit shift which makes the value 160 to be 32 in the stats grid.
* Use the one passed at init time.
*/
if (stats->awb_raw_buffer.meta_data[i + 4 + j * aeGrid_.width] == 0) {
uint8_t Gr = stats->awb_raw_buffer.meta_data[i + 0 + j * aeGrid_.width];
uint8_t Gb = stats->awb_raw_buffer.meta_data[i + 3 + j * aeGrid_.width];
hist[(Gr + Gb) / 2]++;
count++;
}
}
}
/* Limit the gamma effect for now */
gamma_ = 1.1;
/* Estimate the quantile mean of the top 2% of the histogram */
iqMean_ = Histogram(Span<uint32_t>(hist)).interQuantileMean(0.98, 1.0);
}
void IPU3Agc::filterExposure()
{
double speed = 0.2;
if (prevExposure_ == 0.0) {
/* 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 IPU3Agc::lockExposureGain(uint32_t &exposure, uint32_t &gain)
{
updateControls_ = false;
/* 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_;
converged_ = true;
} else {
double newGain = kEvGainTarget * knumHistogramBins / iqMean_;
/* extracted from Rpi::Agc::computeTargetExposure */
double currentShutter = exposure * lineDuration_;
currentExposureNoDg_ = currentShutter * gain;
LOG(IPU3Agc, Debug) << "Actual total exposure " << currentExposureNoDg_
<< " Shutter speed " << currentShutter
<< " Gain " << gain;
currentExposure_ = currentExposureNoDg_ * newGain;
double maxTotalExposure = maxExposureTime_ * kMaxGain;
currentExposure_ = std::min(currentExposure_, maxTotalExposure);
LOG(IPU3Agc, Debug) << "Target total exposure " << currentExposure_;
/* \todo: estimate if we need to desaturate */
filterExposure();
double newExposure = 0.0;
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);
updateControls_ = true;
} 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);
updateControls_ = true;
}
LOG(IPU3Agc, Debug) << "Adjust exposure " << exposure * lineDuration_ << " and gain " << gain;
}
lastFrame_ = frameCount_;
}
void IPU3Agc::process(const ipu3_uapi_stats_3a *stats, uint32_t &exposure, uint32_t &gain)
{
processBrightness(stats);
lockExposureGain(exposure, gain);
frameCount_++;
}
} /* namespace ipa::ipu3 */
} /* namespace libcamera */
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