src/ipa/ipu3/algorithms/af.cpp


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/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
 * Copyright (C) 2021, Red Hat
 *
 * af.cpp - IPU3 auto focus algorithm
 */

#include "af.h"

#include <algorithm>
#include <chrono>
#include <cmath>
#include <fcntl.h>
#include <numeric>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

#include <linux/videodev2.h>

#include <libcamera/base/log.h>

#include <libcamera/ipa/core_ipa_interface.h>

#include "libipa/histogram.h"

/**
 * \file af.h
 */

/*
 * Static variables from ChromiumOS Intel Camera HAL and ia_imaging library:
 * - https://chromium.googlesource.com/chromiumos/platform/arc-camera/+/master/hal/intel/psl/ipu3/statsConverter/ipu3-stats.h
 * - https://chromium.googlesource.com/chromiumos/platform/camera/+/refs/heads/main/hal/intel/ipu3/include/ia_imaging/af_public.h
 */

/** The minimum horizontal grid dimension. */
static constexpr uint8_t kAfMinGridWidth = 16;
/** The minimum vertical grid dimension. */
static constexpr uint8_t kAfMinGridHeight = 16;
/** The maximum horizontal grid dimension. */
static constexpr uint8_t kAfMaxGridWidth = 32;
/** The maximum vertical grid dimension. */
static constexpr uint8_t kAfMaxGridHeight = 24;
/** The minimum value of Log2 of the width of the grid cell. */
static constexpr uint16_t kAfMinGridBlockWidth = 4;
/** The minimum value of Log2 of the height of the grid cell. */
static constexpr uint16_t kAfMinGridBlockHeight = 3;
/** The maximum value of Log2 of the width of the grid cell. */
static constexpr uint16_t kAfMaxGridBlockWidth = 6;
/** The maximum value of Log2 of the height of the grid cell. */
static constexpr uint16_t kAfMaxGridBlockHeight = 6;
/** The number of blocks in vertical axis per slice. */
static constexpr uint16_t kAfDefaultHeightPerSlice = 2;

namespace libcamera {

using namespace std::literals::chrono_literals;

namespace ipa::ipu3::algorithms {

LOG_DEFINE_CATEGORY(IPU3Af)

/**
 * Maximum focus steps of the VCM control
 * \todo should be obtained from the VCM driver
 */
static constexpr uint32_t kMaxFocusSteps = 1023;

/* Minimum focus step for searching appropriate focus */
static constexpr uint32_t kCoarseSearchStep = 30;
static constexpr uint32_t kFineSearchStep = 1;

/* Max ratio of variance change, 0.0 < kMaxChange < 1.0 */
static constexpr double kMaxChange = 0.5;

/* The numbers of frame to be ignored, before performing focus scan. */
static constexpr uint32_t kIgnoreFrame = 10;

/* Fine scan range 0 < kFineRange < 1 */
static constexpr double kFineRange = 0.05;

/* Settings for IPU3 AF filter */
static struct ipu3_uapi_af_filter_config afFilterConfigDefault = {
	.y1_coeff_0 = { 0, 1, 3, 7 },
	.y1_coeff_1 = { 11, 13, 1, 2 },
	.y1_coeff_2 = { 8, 19, 34, 242 },
	.y1_sign_vec = 0x7fdffbfe,
	.y2_coeff_0 = { 0, 1, 6, 6 },
	.y2_coeff_1 = { 13, 25, 3, 0 },
	.y2_coeff_2 = { 25, 3, 177, 254 },
	.y2_sign_vec = 0x4e53ca72,
	.y_calc = { 8, 8, 8, 8 },
	.nf = { 0, 9, 0, 9, 0 },
};

/**
 * \class Af
 * \brief An auto-focus algorithm based on IPU3 statistics
 *
 * This algorithm is used to determine the position of the lens to make a
 * focused image. The IPU3 AF processing block computes the statistics that
 * are composed by two types of filtered value and stores in a AF buffer.
 * Typically, for a clear image, it has a relatively higher contrast than a
 * blurred one. Therefore, if an image with the highest contrast can be
 * found through the scan, the position of the len indicates to a clearest
 * image.
 */
Af::Af()
	: focus_(0), bestFocus_(0), currentVariance_(0.0), previousVariance_(0.0),
	  coarseCompleted_(false), fineCompleted_(false)
{
}

/**
 * \brief Configure the Af given a configInfo
 * \param[in] context The shared IPA context
 * \param[in] configInfo The IPA configuration data
 * \return 0 on success, a negative error code otherwise
 */
int Af::configure(IPAContext &context, const IPAConfigInfo &configInfo)
{
	struct ipu3_uapi_grid_config &grid = context.configuration.af.afGrid;
	grid.width = kAfMinGridWidth;
	grid.height = kAfMinGridHeight;
	grid.block_width_log2 = kAfMinGridBlockWidth;
	grid.block_height_log2 = kAfMinGridBlockHeight;

	/*
	 * \todo - while this clamping code is effectively a no-op, it satisfies
	 * the compiler that the constant definitions of the hardware limits
	 * are used, and paves the way to support dynamic grid sizing in the
	 * future. While the block_{width,height}_log2 remain assigned to the