[libcamera-devel] [PATCH v3 4/5] ipa: rkisp1: agc: Add a histogram-based gain
Jean-Michel Hautbois
jeanmichel.hautbois at ideasonboard.com
Thu Feb 24 12:33:46 CET 2022
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, and use it to populate a vector passed down to the
libipa::Histogram class.
Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois at ideasonboard.com>
Tested-by: Peter Griffin <peter.griffin at linaro.org>
---
v3:
- Don't copy histogram values, pass it to the Histogram class
directly
- Change the date of the copyright
---
src/ipa/rkisp1/algorithms/agc.cpp | 94 ++++++++++++++++++++++++++-----
src/ipa/rkisp1/algorithms/agc.h | 6 +-
src/ipa/rkisp1/ipa_context.cpp | 3 +
src/ipa/rkisp1/ipa_context.h | 1 +
4 files changed, 88 insertions(+), 16 deletions(-)
diff --git a/src/ipa/rkisp1/algorithms/agc.cpp b/src/ipa/rkisp1/algorithms/agc.cpp
index dd97afc0..2e95ee05 100644
--- a/src/ipa/rkisp1/algorithms/agc.cpp
+++ b/src/ipa/rkisp1/algorithms/agc.cpp
@@ -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
*/
@@ -43,18 +45,22 @@ 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.
*
* It's a number that's chosen so that, when the camera points at a grey
* target, the resulting image brightness is considered right.
*
- * \todo Why is the value different between IPU3 and RkISP1 ?
+ * \todo The value is not the same for IPU3 and RkIsp1 because we don't have
+ * sensor degamma yet.
*/
static constexpr double kRelativeLuminanceTarget = 0.4;
Agc::Agc()
- : frameCount_(0), numCells_(0), filteredExposure_(0s)
+ : frameCount_(0), numCells_(0), numHistBins_(0), filteredExposure_(0s)
{
}
@@ -65,8 +71,7 @@ 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 +82,22 @@ 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 +143,9 @@ 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 +154,9 @@ 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 +167,7 @@ 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 +184,13 @@ 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 +261,18 @@ 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 +287,10 @@ 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 = ¶ms->ae;
+ const rkisp1_cif_isp_hist_stat *hist = ¶ms->hist;
+
+ double iqMean = measureBrightness(hist);
+ double iqMeanGain = kEvGainTarget * numHistBins_ / iqMean;
/*
* Estimate the gain needed to achieve a relative luminance target. To
@@ -277,15 +314,44 @@ 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 */
diff --git a/src/ipa/rkisp1/algorithms/agc.h b/src/ipa/rkisp1/algorithms/agc.h
index 942c9d7a..ce1adf27 100644
--- a/src/ipa/rkisp1/algorithms/agc.h
+++ b/src/ipa/rkisp1/algorithms/agc.h
@@ -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.h - RkISP1 AGC/AEC mean-based control algorithm
*/
@@ -32,13 +32,15 @@ public:
void process(IPAContext &context, const rkisp1_stat_buffer *stats) override;
private:
- void computeExposure(IPAContext &Context, double yGain);
+ void computeExposure(IPAContext &Context, double yGain, double iqMeanGain);
utils::Duration filterExposure(utils::Duration exposureValue);
double estimateLuminance(const rkisp1_cif_isp_ae_stat *ae, double gain);
+ double measureBrightness(const rkisp1_cif_isp_hist_stat *hist) const;
uint64_t frameCount_;
uint32_t numCells_;
+ uint32_t numHistBins_;
utils::Duration filteredExposure_;
};
diff --git a/src/ipa/rkisp1/ipa_context.cpp b/src/ipa/rkisp1/ipa_context.cpp
index 664f572f..790e159b 100644
--- a/src/ipa/rkisp1/ipa_context.cpp
+++ b/src/ipa/rkisp1/ipa_context.cpp
@@ -71,6 +71,9 @@ namespace libcamera::ipa::rkisp1 {
* \var IPASessionConfiguration::agc.maxAnalogueGain
* \brief Maximum analogue gain supported with the configured sensor
*
+ * \var IPASessionConfiguration::agc.measureWindow
+ * \brief AGC measure window
+ *
* \var IPASessionConfiguration::hw
* \brief RkISP1-specific hardware information
*
diff --git a/src/ipa/rkisp1/ipa_context.h b/src/ipa/rkisp1/ipa_context.h
index 212fa052..35e9b8e5 100644
--- a/src/ipa/rkisp1/ipa_context.h
+++ b/src/ipa/rkisp1/ipa_context.h
@@ -22,6 +22,7 @@ struct IPASessionConfiguration {
utils::Duration maxShutterSpeed;
double minAnalogueGain;
double maxAnalogueGain;
+ struct rkisp1_cif_isp_window measureWindow;
} agc;
struct {
--
2.32.0
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