ipa: ipu3: Add support for IPU3 AWB algorithm

The IPA will locally modify the parameters before they are passed down
to the ImgU. Use a local parameter object to give a reference to those
algorithms.

Inherit from the Algorithm class to implement basic AWB functions.

The configure() call will set exposure and gain to their minimum value,
so while AGC is not there, the frames will be dark.

Once AWB is done, a color temperature is estimated and a default CCM matrix
will be used (yet to be tuned).
Implement a basic "grey-world" AWB algorithm just for demonstration purpose.

The BDS output size is passed by the pipeline handler to the IPA.
The best grid is then calculated to maximize the number of pixels taken
into account in each cells.

As commented in the source code, it can be improved, as it has (at least)
one limitation: if a cell is big (say 128 pixels wide) and indicated as
saturated, it won't be taken into account at all.
Maybe is it possible to have a smaller one, at the cost of a few pixels
to lose, in which case we can center the grid using the x_start and
y_start parameters.

Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Tested-by: Jacopo Mondi <jacopo@jmondi.org>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

1 files changed, 356 insertions, 0 deletions

diff --git a/src/ipa/ipu3/ipu3_awb.cpp b/src/ipa/ipu3/ipu3_awb.cpp
new file mode 100644
index 00000000..060d1e18
--- /dev/null
+++ b/src/ipa/ipu3/ipu3_awb.cpp
@@ -0,0 +1,356 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2021, Ideas On Board
+ *
+ * ipu3_awb.cpp - AWB control algorithm
+ */
+#include "ipu3_awb.h"
+
+#include <cmath>
+#include <numeric>
+#include <unordered_map>
+
+#include "libcamera/internal/log.h"
+
+namespace libcamera {
+
+namespace ipa::ipu3 {
+
+LOG_DEFINE_CATEGORY(IPU3Awb)
+
+static constexpr uint32_t kMinZonesCounted = 16;
+static constexpr uint32_t kMinGreenLevelInZone = 32;
+
+/**
+ * \struct IspStatsRegion
+ * \brief RGB statistics for a given region
+ *
+ * The IspStatsRegion structure is intended to abstract the ISP specific
+ * statistics and use an agnostic algorithm to compute AWB.
+ *
+ * \var IspStatsRegion::counted
+ * \brief Number of pixels used to calculate the sums
+ *
+ * \var IspStatsRegion::uncounted
+ * \brief Remaining number of pixels in the region
+ *
+ * \var IspStatsRegion::rSum
+ * \brief Sum of the red values in the region
+ *
+ * \var IspStatsRegion::gSum
+ * \brief Sum of the green values in the region
+ *
+ * \var IspStatsRegion::bSum
+ * \brief Sum of the blue values in the region
+ */
+
+/**
+ * \struct AwbStatus
+ * \brief AWB parameters calculated
+ *
+ * The AwbStatus structure is intended to store the AWB
+ * parameters calculated by the algorithm
+ *
+ * \var AwbStatus::temperatureK
+ * \brief Color temperature calculated
+ *
+ * \var AwbStatus::redGain
+ * \brief Gain calculated for the red channel
+ *
+ * \var AwbStatus::greenGain
+ * \brief Gain calculated for the green channel
+ *
+ * \var AwbStatus::blueGain
+ * \brief Gain calculated for the blue channel
+ */
+
+/**
+ * \struct Ipu3AwbCell
+ * \brief Memory layout for each cell in AWB metadata
+ *
+ * The Ipu3AwbCell structure is used to get individual values
+ * such as red average or saturation ratio in a particular cell.
+ *
+ * \var Ipu3AwbCell::greenRedAvg
+ * \brief Green average for red lines in the cell
+ *
+ * \var Ipu3AwbCell::redAvg
+ * \brief Red average in the cell
+ *
+ * \var Ipu3AwbCell::blueAvg
+ * \brief blue average in the cell
+ *
+ * \var Ipu3AwbCell::greenBlueAvg
+ * \brief Green average for blue lines
+ *
+ * \var Ipu3AwbCell::satRatio
+ * \brief Saturation ratio in the cell
+ *
+ * \var Ipu3AwbCell::padding
+ * \brief array of unused bytes for padding
+ */
+
+/* Default settings for Bayer noise reduction replicated from the Kernel */
+static const struct ipu3_uapi_bnr_static_config imguCssBnrDefaults = {
+	.wb_gains = { 16, 16, 16, 16 },
+	.wb_gains_thr = { 255, 255, 255, 255 },
+	.thr_coeffs = { 1700, 0, 31, 31, 0, 16 },
+	.thr_ctrl_shd = { 26, 26, 26, 26 },
+	.opt_center{ -648, 0, -366, 0 },
+	.lut = {
+		{ 17, 23, 28, 32, 36, 39, 42, 45,
+		  48, 51, 53, 55, 58, 60, 62, 64,
+		  66, 68, 70, 72, 73, 75, 77, 78,
+		  80, 82, 83, 85, 86, 88, 89, 90 } },
+	.bp_ctrl = { 20, 0, 1, 40, 0, 6, 0, 6, 0 },
+	.dn_detect_ctrl{ 9, 3, 4, 0, 8, 0, 1, 1, 1, 1, 0 },
+	.column_size = 1296,
+	.opt_center_sqr = { 419904, 133956 },
+};
+
+/* Default settings for Auto White Balance replicated from the Kernel*/
+static const struct ipu3_uapi_awb_config_s imguCssAwbDefaults = {
+	.rgbs_thr_gr = 8191,
+	.rgbs_thr_r = 8191,
+	.rgbs_thr_gb = 8191,
+	.rgbs_thr_b = 8191 | IPU3_UAPI_AWB_RGBS_THR_B_EN | IPU3_UAPI_AWB_RGBS_THR_B_INCL_SAT,
+	.grid = {
+		.width = 160,
+		.height = 36,
+		.block_width_log2 = 3,
+		.block_height_log2 = 4,
+		.height_per_slice = 1, /* Overridden by kernel. */
+		.x_start = 0,
+		.y_start = 0,
+		.x_end = 0,
+		.y_end = 0,
+	},
+};
+
+/* Default color correction matrix defined as an identity matrix */
+static const struct ipu3_uapi_ccm_mat_config imguCssCcmDefault = {
+	8191, 0, 0, 0,
+	0, 8191, 0, 0,
+	0, 0, 8191, 0
+};
+
+IPU3Awb::IPU3Awb()
+	: Algorithm()
+{
+	asyncResults_.blueGain = 1.0;
+	asyncResults_.greenGain = 1.0;
+	asyncResults_.redGain = 1.0;
+	asyncResults_.temperatureK = 4500;
+}
+
+IPU3Awb::~IPU3Awb()
+{
+}
+
+void IPU3Awb::initialise(ipu3_uapi_params &params, const Size &bdsOutputSize, struct ipu3_uapi_grid_config &bdsGrid)
+{
+	params.use.acc_awb = 1;
+	params.acc_param.awb.config = imguCssAwbDefaults;
+
+	awbGrid_ = bdsGrid;
+	params.acc_param.awb.config.grid = awbGrid_;
+
+	params.use.acc_bnr = 1;
+	params.acc_param.bnr = imguCssBnrDefaults;
+	/**
+	 * Optical center is column (respectively row) startminus X (respectively Y) center.
+	 * For the moment use BDS as a first approximation, but it should
+	 * be calculated based on Shading (SHD) parameters.
+	 */
+	params.acc_param.bnr.column_size = bdsOutputSize.width;
+	params.acc_param.bnr.opt_center.x_reset = awbGrid_.x_start - (bdsOutputSize.width / 2);
+	params.acc_param.bnr.opt_center.y_reset = awbGrid_.y_start - (bdsOutputSize.height / 2);
+	params.acc_param.bnr.opt_center_sqr.x_sqr_reset = params.acc_param.bnr.opt_center.x_reset
+							* params.acc_param.bnr.opt_center.x_reset;
+	params.acc_param.bnr.opt_center_sqr.y_sqr_reset = params.acc_param.bnr.opt_center.y_reset
+							* params.acc_param.bnr.opt_center.y_reset;
+
+	params.use.acc_ccm = 1;
+	params.acc_param.ccm = imguCssCcmDefault;
+
+	params.use.acc_gamma = 1;
+	params.acc_param.gamma.gc_ctrl.enable = 1;
+
+	zones_.reserve(kAwbStatsSizeX * kAwbStatsSizeY);
+}
+
+/**
+ * The function estimates the correlated color temperature using
+ * from RGB color space input.
+ * In physics and color science, the Planckian locus or black body locus is
+ * the path or locus that the color of an incandescent black body would take
+ * in a particular chromaticity space as the blackbody temperature changes.
+ *
+ * If a narrow range of color temperatures is considered (those encapsulating
+ * daylight being the most practical case) one can approximate the Planckian
+ * locus in order to calculate the CCT in terms of chromaticity coordinates.
+ *
+ * More detailed information can be found in:
+ * https://en.wikipedia.org/wiki/Color_temperature#Approximation
+ */
+uint32_t IPU3Awb::estimateCCT(double red, double green, double blue)
+{
+	/* Convert the RGB values to CIE tristimulus values (XYZ) */
+	double X = (-0.14282) * (red) + (1.54924) * (green) + (-0.95641) * (blue);
+	double Y = (-0.32466) * (red) + (1.57837) * (green) + (-0.73191) * (blue);
+	double Z = (-0.68202) * (red) + (0.77073) * (green) + (0.56332) * (blue);
+
+	/* Calculate the normalized chromaticity values */
+	double x = X / (X + Y + Z);
+	double y = Y / (X + Y + Z);
+
+	/* Calculate CCT */
+	double n = (x - 0.3320) / (0.1858 - y);
+	return 449 * n * n * n + 3525 * n * n + 6823.3 * n + 5520.33;
+}
+
+/* Generate an RGB vector with the average values for each region */
+void IPU3Awb::generateZones(std::vector<RGB> &zones)
+{
+	for (unsigned int i = 0; i < kAwbStatsSizeX * kAwbStatsSizeY; i++) {
+		RGB zone;
+		double counted = awbStats_[i].counted;
+		if (counted >= kMinZonesCounted) {
+			zone.G = awbStats_[i].gSum / counted;
+			if (zone.G >= kMinGreenLevelInZone) {
+				zone.R = awbStats_[i].rSum / counted;
+				zone.B = awbStats_[i].bSum / counted;
+				zones.push_back(zone);
+			}
+		}
+	}
+}
+
+/* Translate the IPU3 statistics into the default statistics region array */
+void IPU3Awb::generateAwbStats(const ipu3_uapi_stats_3a *stats)
+{
+	uint32_t regionWidth = round(awbGrid_.width / static_cast<double>(kAwbStatsSizeX));
+	uint32_t regionHeight = round(awbGrid_.height / static_cast<double>(kAwbStatsSizeY));
+
+	/*
+	 * Generate a (kAwbStatsSizeX x kAwbStatsSizeY) array from the IPU3 grid which is
+	 * (awbGrid_.width x awbGrid_.height).
+	 */
+	for (unsigned int j = 0; j < kAwbStatsSizeY * regionHeight; j++) {
+		for (unsigned int i = 0; i < kAwbStatsSizeX * regionWidth; i++) {
+			uint32_t cellPosition = j * awbGrid_.width + i;
+			uint32_t cellX = (cellPosition / regionWidth) % kAwbStatsSizeX;
+			uint32_t cellY = ((cellPosition / awbGrid_.width) / regionHeight) % kAwbStatsSizeY;
+
+			uint32_t awbRegionPosition = cellY * kAwbStatsSizeX + cellX;
+			cellPosition *= 8;
+
+			/* Cast the initial IPU3 structure to simplify the reading */
+			Ipu3AwbCell *currentCell = reinterpret_cast<Ipu3AwbCell *>(const_cast<uint8_t *>(&stats->awb_raw_buffer.meta_data[cellPosition]));
+			if (currentCell->satRatio == 0) {
+				/* The cell is not saturated, use the current cell */
+				awbStats_[awbRegionPosition].counted++;
+				uint32_t greenValue = currentCell->greenRedAvg + currentCell->greenBlueAvg;
+				awbStats_[awbRegionPosition].gSum += greenValue / 2;
+				awbStats_[awbRegionPosition].rSum += currentCell->redAvg;
+				awbStats_[awbRegionPosition].bSum += currentCell->blueAvg;
+			}
+		}
+	}
+}
+
+void IPU3Awb::clearAwbStats()
+{
+	for (unsigned int i = 0; i < kAwbStatsSizeX * kAwbStatsSizeY; i++) {
+		awbStats_[i].bSum = 0;
+		awbStats_[i].rSum = 0;
+		awbStats_[i].gSum = 0;
+		awbStats_[i].counted = 0;
+		awbStats_[i].uncounted = 0;
+	}
+}
+
+void IPU3Awb::awbGreyWorld()
+{
+	LOG(IPU3Awb, Debug) << "Grey world AWB";
+	/*
+	 * Make a separate list of the derivatives for each of red and blue, so
+	 * that we can sort them to exclude the extreme gains. We could
+	 * consider some variations, such as normalising all the zones first, or
+	 * doing an L2 average etc.
+	 */
+	std::vector<RGB> &redDerivative(zones_);
+	std::vector<RGB> blueDerivative(redDerivative);
+	std::sort(redDerivative.begin(), redDerivative.end(),
+		  [](RGB const &a, RGB const &b) {
+			  return a.G * b.R < b.G * a.R;
+		  });
+	std::sort(blueDerivative.begin(), blueDerivative.end(),
+		  [](RGB const &a, RGB const &b) {
+			  return a.G * b.B < b.G * a.B;
+		  });
+
+	/* Average the middle half of the values. */
+	int discard = redDerivative.size() / 4;
+
+	RGB sumRed(0, 0, 0);
+	RGB sumBlue(0, 0, 0);
+	for (auto ri = redDerivative.begin() + discard,
+		  bi = blueDerivative.begin() + discard;
+	     ri != redDerivative.end() - discard; ri++, bi++)
+		sumRed += *ri, sumBlue += *bi;
+
+	double redGain = sumRed.G / (sumRed.R + 1),
+	       blueGain = sumBlue.G / (sumBlue.B + 1);
+
+	/* Color temperature is not relevant in Grey world but still useful to estimate it :-) */
+	asyncResults_.temperatureK = estimateCCT(sumRed.R, sumRed.G, sumBlue.B);
+	asyncResults_.redGain = redGain;
+	asyncResults_.greenGain = 1.0;
+	asyncResults_.blueGain = blueGain;
+}
+
+void IPU3Awb::calculateWBGains(const ipu3_uapi_stats_3a *stats)
+{
+	ASSERT(stats->stats_3a_status.awb_en);
+	zones_.clear();
+	clearAwbStats();
+	generateAwbStats(stats);
+	generateZones(zones_);
+	LOG(IPU3Awb, Debug) << "Valid zones: " << zones_.size();
+	if (zones_.size() > 10) {
+		awbGreyWorld();
+		LOG(IPU3Awb, Debug) << "Gain found for red: " << asyncResults_.redGain
+				    << " and for blue: " << asyncResults_.blueGain;
+	}
+}
+
+void IPU3Awb::updateWbParameters(ipu3_uapi_params &params, double agcGamma)
+{
+	/*
+	 * Green gains should not be touched and considered 1.
+	 * Default is 16, so do not change it at all.
+	 * 4096 is the value for a gain of 1.0
+	 */
+	params.acc_param.bnr.wb_gains.gr = 16;
+	params.acc_param.bnr.wb_gains.r = 4096 * asyncResults_.redGain;
+	params.acc_param.bnr.wb_gains.b = 4096 * asyncResults_.blueGain;
+	params.acc_param.bnr.wb_gains.gb = 16;
+
+	LOG(IPU3Awb, Debug) << "Color temperature estimated: " << asyncResults_.temperatureK
+			    << " and gamma calculated: " << agcGamma;
+
+	/* The CCM matrix may change when color temperature will be used */
+	params.acc_param.ccm = imguCssCcmDefault;
+
+	for (uint32_t i = 0; i < 256; i++) {
+		double j = i / 255.0;
+		double gamma = std::pow(j, 1.0 / agcGamma);
+		/* The maximum value 255 is represented on 13 bits in the IPU3 */
+		params.acc_param.gamma.gc_lut.lut[i] = gamma * 8191;
+	}
+}
+
+} /* namespace ipa::ipu3 */
+
+} /* namespace libcamera */