swscale.c

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/*
 * Copyright (C) 2024      Niklas Haas
 * Copyright (C) 2003-2011 Michael Niedermayer <michaelni@gmx.at>
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */
 
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <inttypes.h>
#include <stdarg.h>
#include <signal.h>
 
#undef HAVE_AV_CONFIG_H
#include "libavutil/cpu.h"
#include "libavutil/parseutils.h"
#include "libavutil/pixdesc.h"
#include "libavutil/lfg.h"
#include "libavutil/sfc64.h"
#include "libavutil/frame.h"
#include "libavutil/opt.h"
#include "libavutil/time.h"
#include "libavutil/pixfmt.h"
#include "libavutil/avassert.h"
#include "libavutil/macros.h"
 
#include "libswscale/swscale.h"
 
struct options {
    enum AVPixelFormat src_fmt;
    enum AVPixelFormat dst_fmt;
    double prob;
    int w, h;
    int threads;
    int iters;
    int bench;
    int flags;
    int dither;
    int unscaled;
    int legacy;
    int pretty;
};
 
struct mode {
    SwsFlags flags;
    SwsDither dither;
};
 
struct test_results {
    float ssim[4];
    float loss;
    int64_t time;
    int iters;
};
 
const SwsFlags flags[] = {
    0, // test defaults
    SWS_FAST_BILINEAR,
    SWS_BILINEAR,
    SWS_BICUBIC,
    SWS_X | SWS_BITEXACT,
    SWS_POINT,
    SWS_AREA | SWS_ACCURATE_RND,
    SWS_BICUBIC | SWS_FULL_CHR_H_INT | SWS_FULL_CHR_H_INP,
};
 
static FFSFC64 prng_state;
 
/* reused between tests for efficiency */
static SwsContext *sws_ref_src;
static SwsContext *sws_src_dst;
static SwsContext *sws_dst_out;
 
static double speedup_logavg;
static double speedup_min = 1e10;
static double speedup_max = 0;
static int speedup_count;
 
static const char *speedup_color(double ratio)
{
    return ratio > 10.00 ? "\033[1;94m" : /* bold blue */
           ratio >  2.00 ? "\033[1;32m" : /* bold green */
           ratio >  1.02 ? "\033[32m"   : /* green */
           ratio >  0.98 ? ""           : /* default */
           ratio >  0.90 ? "\033[33m"   : /* yellow */
           ratio >  0.75 ? "\033[31m"   : /* red */
            "\033[1;31m";  /* bold red */
}
 
static void exit_handler(int sig)
{
    if (speedup_count) {
        double ratio = exp(speedup_logavg / speedup_count);
        fprintf(stderr, "Overall speedup=%.3fx %s%s\033[0m, min=%.3fx max=%.3fx\n", ratio,
                speedup_color(ratio), ratio >= 1.0 ? "faster" : "slower",
                speedup_min, speedup_max);
    }
 
    exit(sig);
}
 
/* Estimate luma variance assuming uniform dither noise distribution */
static float estimate_quantization_noise(enum AVPixelFormat fmt)
{
    const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(fmt);
    float variance = 1.0 / 12;
    if (desc->comp[0].depth < 8) {
        /* Extra headroom for very low bit depth output */
        variance *= (8 - desc->comp[0].depth);
    }
 
    if (desc->flags & AV_PIX_FMT_FLAG_FLOAT) {
        return 0.0;
    } else if (desc->flags & AV_PIX_FMT_FLAG_RGB) {
        const float r = 0.299 / (1 << desc->comp[0].depth);
        const float g = 0.587 / (1 << desc->comp[1].depth);
        const float b = 0.114 / (1 << desc->comp[2].depth);
        return (r * r + g * g + b * b) * variance;
    } else {
        const float y = 1.0 / (1 << desc->comp[0].depth);
        return y * y * variance;
    }
}
 
static int fmt_comps(enum AVPixelFormat fmt)
{
    const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(fmt);
    int comps = desc->nb_components >= 3 ? 0x7 : 0x1;
    if (desc->flags & AV_PIX_FMT_FLAG_ALPHA)
        comps |= 0x8;
    return comps;
}
 
static void get_ssim(float ssim[4], const AVFrame *out, const AVFrame *ref, int comps)
{
    av_assert1(out->format == AV_PIX_FMT_YUVA444P);
    av_assert1(ref->format == out->format);
    av_assert1(ref->width == out->width && ref->height == out->height);
 
    for (int p = 0; p < 4; p++) {
        const int stride_a = out->linesize[p];
        const int stride_b = ref->linesize[p];
        const int w = out->width;
        const int h = out->height;
 
        const int is_chroma = p == 1 || p == 2;
        const uint8_t def = is_chroma ? 128 : 0xFF;
        const int has_ref = comps & (1 << p);
        double sum = 0;
        int count = 0;
 
        /* 4x4 SSIM */
        for (int y = 0; y < (h & ~3); y += 4) {
            for (int x = 0; x < (w & ~3); x += 4) {
                const float c1 = .01 * .01 * 255 * 255 * 64;
                const float c2 = .03 * .03 * 255 * 255 * 64 * 63;
                int s1 = 0, s2 = 0, ss = 0, s12 = 0, var, covar;
 
                for (int yy = 0; yy < 4; yy++) {
                    for (int xx = 0; xx < 4; xx++) {
                        int a = out->data[p][(y + yy) * stride_a + x + xx];
                        int b = has_ref ? ref->data[p][(y + yy) * stride_b + x + xx] : def;
                        s1  += a;
                        s2  += b;
                        ss  += a * a + b * b;
                        s12 += a * b;
                    }
                }
 
                var = ss * 64 - s1 * s1 - s2 * s2;
                covar = s12 * 64 - s1 * s2;
                sum += (2 * s1 * s2 + c1) * (2 * covar + c2) /
                       ((s1 * s1 + s2 * s2 + c1) * (var + c2));
                count++;
            }
        }
 
        ssim[p] = count ? sum / count : 0.0;
    }
}
 
static float get_loss(const float ssim[4])
{
    const float weights[3] = { 0.8, 0.1, 0.1 }; /* tuned for Y'CbCr */
 
    float sum = 0;
    for (int i = 0; i < 3; i++)
        sum += weights[i] * ssim[i];
    sum *= ssim[3]; /* ensure alpha errors get caught */
 
    return 1.0 - sum;
}
 
static void unref_buffers(AVFrame *frame)
{
    for (int i = 0; i < FF_ARRAY_ELEMS(frame->buf); i++) {
        if (!frame->buf[i])
            break;
        av_buffer_unref(&frame->buf[i]);
    }
 
    memset(frame->data, 0, sizeof(frame->data));
    memset(frame->linesize, 0, sizeof(frame->linesize));
}
 
static int checked_sws_scale_frame(SwsContext *c, AVFrame *dst, const AVFrame *src)
{
    int ret = sws_scale_frame(c, dst, src);
    if (ret < 0) {
        av_log(NULL, AV_LOG_ERROR, "Failed %s ---> %s\n",
               av_get_pix_fmt_name(src->format), av_get_pix_fmt_name(dst->format));
    }
    return ret;
}
 
static int scale_new(AVFrame *dst, const AVFrame *src,
                     const struct mode *mode, const struct options *opts,
                     int64_t *out_time)
{
    sws_src_dst->flags  = mode->flags;
    sws_src_dst->dither = mode->dither;
    sws_src_dst->threads = opts->threads;
 
    int ret = sws_frame_setup(sws_src_dst, dst, src);
    if (ret < 0) {
        av_log(NULL, AV_LOG_ERROR, "Failed to setup %s ---> %s\n",
               av_get_pix_fmt_name(src->format), av_get_pix_fmt_name(dst->format));
        return ret;
    }
 
    int64_t time = av_gettime_relative();
    for (int i = 0; ret >= 0 && i < opts->iters; i++) {
        unref_buffers(dst);
        ret = checked_sws_scale_frame(sws_src_dst, dst, src);
    }
    *out_time = av_gettime_relative() - time;
 
    return ret;
}
 
static int scale_legacy(AVFrame *dst, const AVFrame *src,
                        const struct mode *mode, const struct options *opts,
                        int64_t *out_time)
{
    SwsContext *sws_legacy;
    int ret;
 
    sws_legacy = sws_alloc_context();
    if (!sws_legacy)
        return -1;
 
    sws_legacy->src_w      = src->width;
    sws_legacy->src_h      = src->height;
    sws_legacy->src_format = src->format;
    sws_legacy->dst_w      = dst->width;
    sws_legacy->dst_h      = dst->height;
    sws_legacy->dst_format = dst->format;
    sws_legacy->flags      = mode->flags;
    sws_legacy->dither     = mode->dither;
    sws_legacy->threads    = opts->threads;
 
    av_frame_unref(dst);
    dst->width  = sws_legacy->dst_w;
    dst->height = sws_legacy->dst_h;
    dst->format = sws_legacy->dst_format;
    ret = av_frame_get_buffer(dst, 0);
    if (ret < 0)
        goto error;
 
    ret = sws_init_context(sws_legacy, NULL, NULL);
    if (ret < 0)
        goto error;
 
    int64_t time = av_gettime_relative();
    for (int i = 0; ret >= 0 && i < opts->iters; i++)
        ret = checked_sws_scale_frame(sws_legacy, dst, src);
    *out_time = av_gettime_relative() - time;
 
error:
    sws_freeContext(sws_legacy);
    return ret;
}
 
static void print_results(const AVFrame *ref, const AVFrame *src, const AVFrame *dst,
                          int dst_w, int dst_h,
                          const struct mode *mode, const struct options *opts,
                          const struct test_results *r,
                          const struct test_results *ref_r,
                          float expected_loss)
{
    if (av_log_get_level() >= AV_LOG_INFO) {
        printf("%-*s %*dx%*d -> %-*s %*dx%*d, flags=0x%0*x dither=%u",
               opts->pretty ? 14 : 0, av_get_pix_fmt_name(src->format),
               opts->pretty ?  4 : 0, src->width,
               opts->pretty ?  4 : 0, src->height,
               opts->pretty ? 14 : 0, av_get_pix_fmt_name(dst->format),
               opts->pretty ?  4 : 0, dst->width,
               opts->pretty ?  4 : 0, dst->height,
               opts->pretty ?  8 : 0, mode->flags,
               mode->dither);
 
        if (!opts->bench || !ref_r) {
            printf(", SSIM={Y=%f U=%f V=%f A=%f} loss=%e",
                   r->ssim[0], r->ssim[1], r->ssim[2], r->ssim[3],
                   r->loss);
            if (ref_r)
                printf(" (ref=%e)", ref_r->loss);
        }
 
        if (opts->bench) {
            printf(", time=%*"PRId64"/%u us",
                   opts->pretty ? 7 : 0, r->time, opts->iters);
            if (ref_r) {
                double ratio = ((double) ref_r->time / ref_r->iters)
                             / ((double) r->time / opts->iters);
                if (FFMIN(r->time, ref_r->time) > 100 /* don't pollute stats with low precision */) {
                    speedup_min = FFMIN(speedup_min, ratio);
                    speedup_max = FFMAX(speedup_max, ratio);
                    speedup_logavg += log(ratio);
                    speedup_count++;
                }
 
                printf(" (ref=%*"PRId64"/%u us), speedup=%*.3fx %s%s\033[0m",
                       opts->pretty ? 7 : 0, ref_r->time, ref_r->iters,
                       opts->pretty ? 6 : 0, ratio,
                       speedup_color(ratio), ratio >= 1.0 ? "faster" : "slower");
            }
        }
        printf("\n");
 
        fflush(stdout);
    }
 
    if (r->loss - expected_loss > 1e-4 && dst_w >= ref->width && dst_h >= ref->height) {
        const int bad = r->loss - expected_loss > 1e-2;
        const int level = bad ? AV_LOG_ERROR : AV_LOG_WARNING;
        const char *worse_str = bad ? "WORSE" : "worse";
        av_log(NULL, level,
               "  loss %e is %s by %e, expected loss %e\n",
               r->loss, worse_str, r->loss - expected_loss, expected_loss);
    }
 
    if (ref_r && r->loss - ref_r->loss > 1e-4) {
        /**
         * The new scaling code does not (yet) perform error diffusion for
         * low bit depth output, which impacts the SSIM score slightly for
         * very low bit-depth formats (e.g. monow, monob). Since this is an
         * expected result, drop the badness from an error to a warning for
         * such cases. This can be removed again once error diffusion is
         * implemented in the new ops code.
         */
        const int dst_bits = av_pix_fmt_desc_get(dst->format)->comp[0].depth;
        const int bad = r->loss - ref_r->loss > 1e-2 && dst_bits > 1;
        const int level = bad ? AV_LOG_ERROR : AV_LOG_WARNING;
        const char *worse_str = bad ? "WORSE" : "worse";
        av_log(NULL, level,
               "  loss %e is %s by %e, ref loss %e SSIM={Y=%f U=%f V=%f A=%f}\n",
               r->loss, worse_str, r->loss - ref_r->loss, ref_r->loss,
               ref_r->ssim[0], ref_r->ssim[1], ref_r->ssim[2], ref_r->ssim[3]);
    }
}
 
static int init_frame(AVFrame **pframe, const AVFrame *ref,
                      int width, int height, enum AVPixelFormat format)
{
    AVFrame *frame = av_frame_alloc();
    if (!frame)
        return AVERROR(ENOMEM);
    av_frame_copy_props(frame, ref);
    frame->width  = width;
    frame->height = height;
    frame->format = format;
    *pframe = frame;
    return 0;
}
 
/* Runs a series of ref -> src -> dst -> out, and compares out vs ref */
static int run_test(enum AVPixelFormat src_fmt, enum AVPixelFormat dst_fmt,
                    int dst_w, int dst_h,
                    const struct mode *mode, const struct options *opts,
                    const AVFrame *ref, AVFrame *src,
                    const struct test_results *ref_r)
{
    AVFrame *dst = NULL, *out = NULL;
    const int comps = fmt_comps(src_fmt) & fmt_comps(dst_fmt);
    int ret;
 
    /* Estimate the expected amount of loss from bit depth reduction */
    const float c1 = 0.01 * 0.01; /* stabilization constant */
    const float ref_var = 1.0 / 12.0; /* uniformly distributed signal */
    const float src_var = estimate_quantization_noise(src_fmt);
    const float dst_var = estimate_quantization_noise(dst_fmt);
    const float out_var = estimate_quantization_noise(ref->format);
    const float total_var = src_var + dst_var + out_var;
    const float ssim_luma = (2 * ref_var + c1) / (2 * ref_var + total_var + c1);
    const float ssim_expected[4] = { ssim_luma, 1, 1, 1 }; /* for simplicity */
    const float expected_loss = get_loss(ssim_expected);
 
    struct test_results r = { 0 };
 
    if (src->format != src_fmt) {
        av_frame_unref(src);
        av_frame_copy_props(src, ref);
        src->width  = ref->width;
        src->height = ref->height;
        src->format = src_fmt;
        ret = checked_sws_scale_frame(sws_ref_src, src, ref);
        if (ret < 0)
            goto error;
    }
 
    ret = init_frame(&dst, ref, dst_w, dst_h, dst_fmt);
    if (ret < 0)
        goto error;
 
    ret = opts->legacy ? scale_legacy(dst, src, mode, opts, &r.time)
                       : scale_new(dst, src, mode, opts, &r.time);
    if (ret < 0)
        goto error;
 
    ret = init_frame(&out, ref, ref->width, ref->height, ref->format);
    if (ret < 0)
        goto error;
 
    ret = checked_sws_scale_frame(sws_dst_out, out, dst);
    if (ret < 0)
        goto error;
 
    get_ssim(r.ssim, out, ref, comps);
 
    if (opts->legacy) {
        /* Legacy swscale does not perform bit accurate upconversions of low
         * bit depth RGB. This artificially improves the SSIM score because the
         * resulting error deletes some of the input dither noise. This gives
         * it an unfair advantage when compared against a bit exact reference.
         * Work around this by ensuring that the resulting SSIM score is not
         * higher than it theoretically "should" be. */
        if (src_var > dst_var) {
            const float src_loss = (2 * ref_var + c1) / (2 * ref_var + src_var + c1);
            r.ssim[0] = FFMIN(r.ssim[0], src_loss);
        }
    }
 
    r.loss = get_loss(r.ssim);
    if (!opts->legacy && r.loss - expected_loss > 1e-2 && dst_w >= ref->width && dst_h >= ref->height) {
        ret = -1;
        goto bad_loss;
    }
 
    if (ref_r && r.loss - ref_r->loss > 1e-2) {
        ret = -1;
        goto bad_loss;
    }
 
    ret = 0; /* fall through */
 
bad_loss:
    print_results(ref, src, dst,
                  dst_w, dst_h,
                  mode, opts,
                  &r, ref_r,
                  expected_loss);
 
 error:
    av_frame_free(&dst);
    av_frame_free(&out);
    return ret;
}
 
static inline int fmt_is_subsampled(enum AVPixelFormat fmt)
{
    return av_pix_fmt_desc_get(fmt)->log2_chroma_w != 0 ||
           av_pix_fmt_desc_get(fmt)->log2_chroma_h != 0;
}
 
static int run_self_tests(const AVFrame *ref, const struct options *opts)
{
    const int dst_w[] = { opts->w, opts->w - opts->w / 3, opts->w + opts->w / 3 };
    const int dst_h[] = { opts->h, opts->h - opts->h / 3, opts->h + opts->h / 3 };
 
    enum AVPixelFormat src_fmt, dst_fmt,
                       src_fmt_min = 0,
                       dst_fmt_min = 0,
                       src_fmt_max = AV_PIX_FMT_NB - 1,
                       dst_fmt_max = AV_PIX_FMT_NB - 1;
 
    AVFrame *src = av_frame_alloc();
    if (!src)
        return AVERROR(ENOMEM);
 
    int ret = 0;
 
    if (opts->src_fmt != AV_PIX_FMT_NONE)
        src_fmt_min = src_fmt_max = opts->src_fmt;
    if (opts->dst_fmt != AV_PIX_FMT_NONE)
        dst_fmt_min = dst_fmt_max = opts->dst_fmt;
 
    for (src_fmt = src_fmt_min; src_fmt <= src_fmt_max; src_fmt++) {
        if (opts->unscaled && fmt_is_subsampled(src_fmt))
            continue;
        if (!sws_test_format(src_fmt, 0) || !sws_test_format(src_fmt, 1))
            continue;
        for (dst_fmt = dst_fmt_min; dst_fmt <= dst_fmt_max; dst_fmt++) {
            if (opts->unscaled && fmt_is_subsampled(dst_fmt))
                continue;
            if (!sws_test_format(dst_fmt, 0) || !sws_test_format(dst_fmt, 1))
                continue;
            for (int h = 0; h < FF_ARRAY_ELEMS(dst_h); h++) {
                for (int w = 0; w < FF_ARRAY_ELEMS(dst_w); w++) {
                    for (int f = 0; f < FF_ARRAY_ELEMS(flags); f++) {
                        struct mode mode = {
                            .flags  = opts->flags  >= 0 ? opts->flags  : flags[f],
                            .dither = opts->dither >= 0 ? opts->dither : SWS_DITHER_AUTO,
                        };
 
                        if (ff_sfc64_get(&prng_state) > UINT64_MAX * opts->prob)
                            continue;
 
                        ret = run_test(src_fmt, dst_fmt, dst_w[w], dst_h[h],
                                       &mode, opts, ref, src, NULL);
                        if (ret < 0)
                            goto error;
 
                        if (opts->flags >= 0 || opts->unscaled)
                            break;
                    }
                    if (opts->unscaled)
                        break;
                }
                if (opts->unscaled)
                    break;
            }
        }
    }
 
    ret = 0;
 
error:
    av_frame_free(&src);
    return ret;
}
 
static int run_file_tests(const AVFrame *ref, FILE *fp, const struct options *opts)
{
    char buf[256];
    int ret = 0;
 
    AVFrame *src = av_frame_alloc();
    if (!src)
        return AVERROR(ENOMEM);
 
    for (int line = 1; fgets(buf, sizeof(buf), fp); line++) {
        char src_fmt_str[21], dst_fmt_str[21];
        enum AVPixelFormat src_fmt;
        enum AVPixelFormat dst_fmt;
        int sw, sh, dw, dh;
        struct test_results r = { 0 };
        struct mode mode;
        int n = 0;
 
        ret = sscanf(buf,
                     "%20s %dx%d -> %20s %dx%d, flags=0x%x dither=%u, "
                     "SSIM={Y=%f U=%f V=%f A=%f} loss=%e%n",
                     src_fmt_str, &sw, &sh, dst_fmt_str, &dw, &dh,
                     &mode.flags, &mode.dither,
                     &r.ssim[0], &r.ssim[1], &r.ssim[2], &r.ssim[3],
                     &r.loss, &n);
        if (ret != 13) {
            av_log(NULL, AV_LOG_FATAL,
                   "Malformed reference file in line %d\n", line);
            goto error;
        }
        if (opts->bench) {
            ret = sscanf(buf + n,
                         ", time=%"PRId64"/%u us",
                         &r.time, &r.iters);
            if (ret != 2) {
                av_log(NULL, AV_LOG_FATAL,
                       "Missing benchmarks from reference file in line %d\n",
                       line);
                goto error;
            }
        }
 
        src_fmt = av_get_pix_fmt(src_fmt_str);
        dst_fmt = av_get_pix_fmt(dst_fmt_str);
        if (src_fmt == AV_PIX_FMT_NONE || dst_fmt == AV_PIX_FMT_NONE) {
            av_log(NULL, AV_LOG_FATAL,
                   "Unknown pixel formats (%s and/or %s) in line %d\n",
                   src_fmt_str, dst_fmt_str, line);
            goto error;
        }
 
        if (sw != ref->width || sh != ref->height) {
            av_log(NULL, AV_LOG_FATAL,
                   "Mismatching dimensions %dx%d (ref is %dx%d) in line %d\n",
                   sw, sh, ref->width, ref->height, line);
            goto error;
        }
 
        if (opts->src_fmt != AV_PIX_FMT_NONE && src_fmt != opts->src_fmt ||
            opts->dst_fmt != AV_PIX_FMT_NONE && dst_fmt != opts->dst_fmt)
            continue;
 
        ret = run_test(src_fmt, dst_fmt, dw, dh, &mode, opts, ref, src, &r);
        if (ret < 0)
            goto error;
    }
 
    ret = 0;
 
error:
    av_frame_free(&src);
    return ret;
}
 
static int init_ref(AVFrame *ref, const struct options *opts)
{
    SwsContext *ctx = sws_alloc_context();
    AVFrame *rgb = av_frame_alloc();
    AVLFG rand;
    int ret = -1;
 
    if (!ctx || !rgb)
        goto error;
 
    rgb->width  = opts->w / 12;
    rgb->height = opts->h / 12;
    rgb->format = AV_PIX_FMT_RGBA;
    ret = av_frame_get_buffer(rgb, 32);
    if (ret < 0)
        goto error;
 
    av_lfg_init(&rand, 1);
    for (int y = 0; y < rgb->height; y++) {
        for (int x = 0; x < rgb->width; x++) {
            for (int c = 0; c < 4; c++)
                rgb->data[0][y * rgb->linesize[0] + x * 4 + c] = av_lfg_get(&rand);
        }
    }
 
    ctx->flags = SWS_BILINEAR | SWS_BITEXACT | SWS_ACCURATE_RND;
    ret = checked_sws_scale_frame(ctx, ref, rgb);
 
error:
    sws_free_context(&ctx);
    av_frame_free(&rgb);
    return ret;
}
 
static int parse_options(int argc, char **argv, struct options *opts, FILE **fp)
{
    for (int i = 1; i < argc; i += 2) {
        if (!strcmp(argv[i], "-help") || !strcmp(argv[i], "--help")) {
            fprintf(stderr,
                    "swscale [options...]\n"
                    "   -help\n"
                    "       This text\n"
                    "   -ref <file>\n"
                    "       Uses file as reference to compare tests against. Tests that have become worse will contain the string worse or WORSE\n"
                    "   -p <number between 0.0 and 1.0>\n"
                    "       The percentage of tests or comparisons to perform. Doing all tests will take long and generate over a hundred MB text output\n"
                    "       It is often convenient to perform a random subset\n"
                    "   -dst <pixfmt>\n"
                    "       Only test the specified destination pixel format\n"
                    "   -src <pixfmt>\n"
                    "       Only test the specified source pixel format\n"
                    "   -s <size>\n"
                    "       Set frame size (WxH or abbreviation)\n"
                    "   -bench <iters>\n"
                    "       Run benchmarks with the specified number of iterations. This mode also sets the frame size to 1920x1080 (unless -s is specified)\n"
                    "   -flags <flags>\n"
                    "       Test with a specific combination of flags\n"
                    "   -dither <mode>\n"
                    "       Test with a specific dither mode\n"
                    "   -unscaled <1 or 0>\n"
                    "       If 1, test only conversions that do not involve scaling\n"
                    "   -legacy <1 or 0>\n"
                    "       If 1, force using legacy swscale for the main conversion\n"
                    "   -threads <threads>\n"
                    "       Use the specified number of threads\n"
                    "   -cpuflags <cpuflags>\n"
                    "       Uses the specified cpuflags in the tests\n"
                    "   -pretty <1 or 0>\n"
                    "       Align fields while printing results\n"
                    "   -v <level>\n"
                    "       Enable log verbosity at given level\n"
            );
            exit(0);
        }
        if (argv[i][0] != '-' || i + 1 == argc)
            goto bad_option;
        if (!strcmp(argv[i], "-ref")) {
            *fp = fopen(argv[i + 1], "r");
            if (!*fp) {
                fprintf(stderr, "could not open '%s'\n", argv[i + 1]);
                return -1;
            }
        } else if (!strcmp(argv[i], "-cpuflags")) {
            unsigned flags = av_get_cpu_flags();
            int res = av_parse_cpu_caps(&flags, argv[i + 1]);
            if (res < 0) {
                fprintf(stderr, "invalid cpu flags %s\n", argv[i + 1]);
                return -1;
            }
            av_force_cpu_flags(flags);
        } else if (!strcmp(argv[i], "-src")) {
            opts->src_fmt = av_get_pix_fmt(argv[i + 1]);
            if (opts->src_fmt == AV_PIX_FMT_NONE) {
                fprintf(stderr, "invalid pixel format %s\n", argv[i + 1]);
                return -1;
            }
        } else if (!strcmp(argv[i], "-dst")) {
            opts->dst_fmt = av_get_pix_fmt(argv[i + 1]);
            if (opts->dst_fmt == AV_PIX_FMT_NONE) {
                fprintf(stderr, "invalid pixel format %s\n", argv[i + 1]);
                return -1;
            }
        } else if (!strcmp(argv[i], "-s")) {
            if (av_parse_video_size(&opts->w, &opts->h, argv[i + 1]) < 0) {
                fprintf(stderr, "invalid frame size %s\n", argv[i + 1]);
                return -1;
            }
        } else if (!strcmp(argv[i], "-bench")) {
            int iters = atoi(argv[i + 1]);
            if (iters <= 0) {
                opts->bench = 0;
                opts->iters = 1;
            } else {
                opts->bench = 1;
                opts->iters = iters;
            }
        } else if (!strcmp(argv[i], "-flags")) {
            SwsContext *dummy = sws_alloc_context();
            const AVOption *flags_opt = av_opt_find(dummy, "sws_flags", NULL, 0, 0);
            int ret = av_opt_eval_flags(dummy, flags_opt, argv[i + 1], &opts->flags);
            sws_free_context(&dummy);
            if (ret < 0) {
                fprintf(stderr, "invalid flags %s\n", argv[i + 1]);
                return -1;
            }
        } else if (!strcmp(argv[i], "-dither")) {
            opts->dither = atoi(argv[i + 1]);
        } else if (!strcmp(argv[i], "-unscaled")) {
            opts->unscaled = atoi(argv[i + 1]);
        } else if (!strcmp(argv[i], "-legacy")) {
            opts->legacy = atoi(argv[i + 1]);
        } else if (!strcmp(argv[i], "-threads")) {
            opts->threads = atoi(argv[i + 1]);
        } else if (!strcmp(argv[i], "-p")) {
            opts->prob = atof(argv[i + 1]);
        } else if (!strcmp(argv[i], "-pretty")) {
            opts->pretty = atoi(argv[i + 1]);
        } else if (!strcmp(argv[i], "-v")) {
            av_log_set_level(atoi(argv[i + 1]));
        } else {
bad_option:
            fprintf(stderr, "bad option or argument missing (%s) see -help\n", argv[i]);
            return -1;
        }
    }
 
    if (opts->w < 0 || opts->h < 0) {
        opts->w = opts->bench ? 1920 : 96;
        opts->h = opts->bench ? 1080 : 96;
    }
 
    return 0;
}
 
int main(int argc, char **argv)
{
    struct options opts = {
        .src_fmt = AV_PIX_FMT_NONE,
        .dst_fmt = AV_PIX_FMT_NONE,
        .w       = -1,
        .h       = -1,
        .threads = 1,
        .iters   = 1,
        .prob    = 1.0,
        .flags   = -1,
        .dither  = -1,
    };
 
    AVFrame *ref = NULL;
    FILE *fp = NULL;
    int ret = -1;
 
    if (parse_options(argc, argv, &opts, &fp) < 0)
        goto error;
 
    ff_sfc64_init(&prng_state, 0, 0, 0, 12);
    signal(SIGINT, exit_handler);
 
    sws_ref_src = sws_alloc_context();
    sws_src_dst = sws_alloc_context();
    sws_dst_out = sws_alloc_context();
    if (!sws_ref_src || !sws_src_dst || !sws_dst_out)
        goto error;
    sws_ref_src->flags = SWS_BILINEAR | SWS_BITEXACT | SWS_ACCURATE_RND;
    sws_dst_out->flags = SWS_BILINEAR | SWS_BITEXACT | SWS_ACCURATE_RND;
 
    ref = av_frame_alloc();
    if (!ref)
        goto error;
    ref->width  = opts.w;
    ref->height = opts.h;
    ref->format = AV_PIX_FMT_YUVA444P;
 
    ret = init_ref(ref, &opts);
    if (ret < 0)
        goto error;
 
    ret = fp ? run_file_tests(ref, fp, &opts)
             : run_self_tests(ref, &opts);
 
    /* fall through */
error:
    sws_free_context(&sws_ref_src);
    sws_free_context(&sws_src_dst);
    sws_free_context(&sws_dst_out);
    av_frame_free(&ref);
    if (fp)
        fclose(fp);
    exit_handler(ret);
}