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ipa: rkisp1: agc: Add a histogram-based gain

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As for the IPU3, we can estimate the histogram of the luminance. The
RkISP1 can estimate multiple ones, the R, G and B ones, the Y only one
and a combination of RGB. The one we are interested by in AGC is the Y
histogram.

Use the hardware revision to determine the number of bins of the
produced histogram.

Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
Tested-by: Peter Griffin <peter.griffin@linaro.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
This commit is contained in:
Jean-Michel Hautbois 2022-02-24 12:33:46 +01:00
parent 88c69f8808
commit 8917c9e7ba
4 changed files with 86 additions and 15 deletions
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91
src/ipa/rkisp1/algorithms/agc.cpp
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@ -1,6 +1,6 @@
/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
* Copyright (C) 2021, Ideas On Board
* Copyright (C) 2021-2022, Ideas On Board
*
* agc.cpp - AGC/AEC mean-based control algorithm
*/
@ -16,6 +16,8 @@
#include <libcamera/ipa/core_ipa_interface.h>
#include "libipa/histogram.h"
/**
* \file agc.h
*/
@ -43,6 +45,9 @@ static constexpr utils::Duration kMaxShutterSpeed = 60ms;
/* Number of frames to wait before calculating stats on minimum exposure */
static constexpr uint32_t kNumStartupFrames = 10;
/* Target value to reach for the top 2% of the histogram */
static constexpr double kEvGainTarget = 0.5;
/*
* Relative luminance target.
*
@ -54,7 +59,7 @@ static constexpr uint32_t kNumStartupFrames = 10;
static constexpr double kRelativeLuminanceTarget = 0.4;
Agc::Agc()
: frameCount_(0), numCells_(0), filteredExposure_(0s)
: frameCount_(0), numCells_(0), numHistBins_(0), filteredExposure_(0s)
{
}
@ -65,8 +70,7 @@ Agc::Agc()
*
* \return 0
*/
int Agc::configure(IPAContext &context,
[[maybe_unused]] const IPACameraSensorInfo &configInfo)
int Agc::configure(IPAContext &context, const IPACameraSensorInfo &configInfo)
{
/* Configure the default exposure and gain. */
context.frameContext.agc.gain = std::max(context.configuration.agc.minAnalogueGain, kMinAnalogueGain);
@ -77,10 +81,22 @@ int Agc::configure(IPAContext &context,
* - versions < V12 have RKISP1_CIF_ISP_AE_MEAN_MAX_V10 entries,
* - versions >= V12 have RKISP1_CIF_ISP_AE_MEAN_MAX_V12 entries.
*/
if (context.configuration.hw.revision < RKISP1_V12)
if (context.configuration.hw.revision < RKISP1_V12) {
numCells_ = RKISP1_CIF_ISP_AE_MEAN_MAX_V10;
else
numHistBins_ = RKISP1_CIF_ISP_HIST_BIN_N_MAX_V10;
} else {
numCells_ = RKISP1_CIF_ISP_AE_MEAN_MAX_V12;
numHistBins_ = RKISP1_CIF_ISP_HIST_BIN_N_MAX_V12;
}
/*
* Define the measurement window for AGC as a centered rectangle
* covering 3/4 of the image width and height.
*/
context.configuration.agc.measureWindow.h_offs = configInfo.outputSize.width / 8;
context.configuration.agc.measureWindow.v_offs = configInfo.outputSize.height / 8;
context.configuration.agc.measureWindow.h_size = 3 * configInfo.outputSize.width / 4;
context.configuration.agc.measureWindow.v_size = 3 * configInfo.outputSize.height / 4;
/* \todo Use actual frame index by populating it in the frameContext. */
frameCount_ = 0;
@ -126,8 +142,9 @@ utils::Duration Agc::filterExposure(utils::Duration exposureValue)
* \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
* \param[in] iqMeanGain The gain calculated based on the relative luminance target
*/
void Agc::computeExposure(IPAContext &context, double yGain)
void Agc::computeExposure(IPAContext &context, double yGain, double iqMeanGain)
{
IPASessionConfiguration &configuration = context.configuration;
IPAFrameContext &frameContext = context.frameContext;
@ -136,6 +153,9 @@ void Agc::computeExposure(IPAContext &context, double yGain)
uint32_t exposure = frameContext.sensor.exposure;
double analogueGain = frameContext.sensor.gain;
/* Use the highest of the two gain estimates. */
double evGain = std::max(yGain, iqMeanGain);
utils::Duration minShutterSpeed = configuration.agc.minShutterSpeed;
utils::Duration maxShutterSpeed = std::min(configuration.agc.maxShutterSpeed,
kMaxShutterSpeed);
@ -146,7 +166,7 @@ void Agc::computeExposure(IPAContext &context, double yGain)
kMaxAnalogueGain);
/* Consider within 1% of the target as correctly exposed. */
if (utils::abs_diff(yGain, 1.0) < 0.01)
if (utils::abs_diff(evGain, 1.0) < 0.01)
return;
/* extracted from Rpi::Agc::computeTargetExposure. */
@ -163,13 +183,13 @@ void Agc::computeExposure(IPAContext &context, double yGain)
LOG(RkISP1Agc, Debug) << "Actual total exposure " << currentShutter * analogueGain
<< " Shutter speed " << currentShutter
<< " Gain " << analogueGain
<< " Needed ev gain " << yGain;
<< " Needed ev gain " << evGain;
/*
* Calculate the current exposure value for the scene as the latest
* exposure value applied multiplied by the new estimated gain.
*/
utils::Duration exposureValue = effectiveExposureValue * yGain;
utils::Duration exposureValue = effectiveExposureValue * evGain;
/* Clamp the exposure value to the min and max authorized. */
utils::Duration maxTotalExposure = maxShutterSpeed * maxAnalogueGain;
@ -240,6 +260,18 @@ double Agc::estimateLuminance(const rkisp1_cif_isp_ae_stat *ae,
return ySum / numCells_ / 255;
}
/**
* \brief Estimate the mean value of the top 2% of the histogram
* \param[in] hist The histogram statistics computed by the ImgU
* \return The mean value of the top 2% of the histogram
*/
double Agc::measureBrightness(const rkisp1_cif_isp_hist_stat *hist) const
{
Histogram histogram{ Span<const uint32_t>(hist->hist_bins, numHistBins_) };
/* Estimate the quantile mean of the top 2% of the histogram. */
return histogram.interQuantileMean(0.98, 1.0);
}
/**
* \brief Process RkISP1 statistics, and run AGC operations
* \param[in] context The shared IPA context
@ -254,6 +286,10 @@ void Agc::process(IPAContext &context, const rkisp1_stat_buffer *stats)
ASSERT(stats->meas_type & RKISP1_CIF_ISP_STAT_AUTOEXP);
const rkisp1_cif_isp_ae_stat *ae = &params->ae;
const rkisp1_cif_isp_hist_stat *hist = &params->hist;
double iqMean = measureBrightness(hist);
double iqMeanGain = kEvGainTarget * numHistBins_ / iqMean;
/*
* Estimate the gain needed to achieve a relative luminance target. To
@ -277,15 +313,44 @@ void Agc::process(IPAContext &context, const rkisp1_stat_buffer *stats)
break;
}
computeExposure(context, yGain);
computeExposure(context, yGain, iqMeanGain);
frameCount_++;
}
void Agc::prepare([[maybe_unused]] IPAContext &context,
rkisp1_params_cfg *params)
/**
* \copydoc libcamera::ipa::Algorithm::prepare
*/
void Agc::prepare(IPAContext &context, rkisp1_params_cfg *params)
{
if (context.frameContext.frameCount > 0)
return;
/* Configure the measurement window. */
params->meas.aec_config.meas_window = context.configuration.agc.measureWindow;
/* Use a continuous method for measure. */
params->meas.aec_config.autostop = RKISP1_CIF_ISP_EXP_CTRL_AUTOSTOP_0;
/* Estimate Y as (R + G + B) x (85/256). */
params->meas.aec_config.mode = RKISP1_CIF_ISP_EXP_MEASURING_MODE_1;
params->module_cfg_update |= RKISP1_CIF_ISP_MODULE_AEC;
params->module_ens |= RKISP1_CIF_ISP_MODULE_AEC;
params->module_en_update |= RKISP1_CIF_ISP_MODULE_AEC;
/* Configure histogram. */
params->meas.hst_config.meas_window = context.configuration.agc.measureWindow;
/* Produce the luminance histogram. */
params->meas.hst_config.mode = RKISP1_CIF_ISP_HISTOGRAM_MODE_Y_HISTOGRAM;
/* Set an average weighted histogram. */
for (unsigned int histBin = 0; histBin < numHistBins_; histBin++)
params->meas.hst_config.hist_weight[histBin] = 1;
/* Step size can't be less than 3. */
params->meas.hst_config.histogram_predivider = 4;
/* Update the configuration for histogram. */
params->module_cfg_update |= RKISP1_CIF_ISP_MODULE_HST;
/* Enable the histogram measure unit. */
params->module_ens |= RKISP1_CIF_ISP_MODULE_HST;
params->module_en_update |= RKISP1_CIF_ISP_MODULE_HST;
}
} /* namespace ipa::rkisp1::algorithms */