FFmpeg/libavfilter/vf_aspect.c

/*
 * Copyright (c) 2010 Bobby Bingham

 * This file is part of Libav.
 *
 * Libav 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.
 *
 * Libav 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 Libav; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

/**
 * @file
 * aspect ratio modification video filters
 */

#include <float.h>

#include "libavutil/common.h"
#include "libavutil/eval.h"
#include "libavutil/mathematics.h"
#include "libavutil/opt.h"
#include "libavutil/parseutils.h"
#include "libavutil/pixdesc.h"

#include "avfilter.h"
#include "internal.h"
#include "video.h"

static const char *const var_names[] = {
    "PI",
    "PHI",
    "E",
    "w",
    "h",
    "a", "dar",
    "sar",
    "hsub",
    "vsub",
    NULL
};

enum var_name {
    VAR_PI,
    VAR_PHI,
    VAR_E,
    VAR_W,
    VAR_H,
    VAR_A, VAR_DAR,
    VAR_SAR,
    VAR_HSUB,
    VAR_VSUB,
    VARS_NB
};

typedef struct AspectContext {
    const AVClass *class;
    AVRational dar;
    AVRational sar;
    char *ratio_expr;
} AspectContext;

static int filter_frame(AVFilterLink *link, AVFrame *frame)
{
    AspectContext *s = link->dst->priv;

    frame->sample_aspect_ratio = s->sar;
    return ff_filter_frame(link->dst->outputs[0], frame);
}

#define OFFSET(x) offsetof(AspectContext, x)
#define FLAGS AV_OPT_FLAG_VIDEO_PARAM

static int get_aspect_ratio(AVFilterLink *inlink, AVRational *aspect_ratio)
{
    AVFilterContext *ctx = inlink->dst;
    AspectContext *s = inlink->dst->priv;
    const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
    double var_values[VARS_NB], res;
    int ret;

    var_values[VAR_PI]    = M_PI;
    var_values[VAR_PHI]   = M_PHI;
    var_values[VAR_E]     = M_E;
    var_values[VAR_W]     = inlink->w;
    var_values[VAR_H]     = inlink->h;
    var_values[VAR_A]     = (double) inlink->w / inlink->h;
    var_values[VAR_SAR]   = inlink->sample_aspect_ratio.num ?
        (double) inlink->sample_aspect_ratio.num / inlink->sample_aspect_ratio.den : 1;
    var_values[VAR_DAR]   = var_values[VAR_A] * var_values[VAR_SAR];
    var_values[VAR_HSUB]  = 1 << desc->log2_chroma_w;
    var_values[VAR_VSUB]  = 1 << desc->log2_chroma_h;

    /* evaluate new aspect ratio*/
    if ((ret = av_expr_parse_and_eval(&res, s->ratio_expr,
                                      var_names, var_values,
                                      NULL, NULL, NULL, NULL, NULL, 0, ctx)) < 0) {
        av_log(NULL, AV_LOG_ERROR,
               "Error when evaluating the expression '%s'\n", s->ratio_expr);
        return ret;
    }
    *aspect_ratio = av_d2q(res, INT_MAX);
    return 0;
}

#if CONFIG_SETDAR_FILTER
/* for setdar filter, convert from frame aspect ratio to pixel aspect ratio */
static int setdar_config_props(AVFilterLink *inlink)
{
    AspectContext *s = inlink->dst->priv;
    AVRational dar;
    int ret;

    if ((ret = get_aspect_ratio(inlink, &s->dar)))
        return ret;

    if (s->dar.num && s->dar.den) {
        av_reduce(&s->sar.num, &s->sar.den,
                   s->dar.num * inlink->h,
                   s->dar.den * inlink->w, 100);
        inlink->sample_aspect_ratio = s->sar;
        dar = s->dar;
    } else {
        inlink->sample_aspect_ratio = (AVRational){ 1, 1 };
        dar = (AVRational){ inlink->w, inlink->h };
    }

    av_log(inlink->dst, AV_LOG_VERBOSE, "w:%d h:%d -> dar:%d/%d sar:%d/%d\n",
           inlink->w, inlink->h, dar.num, dar.den,
           inlink->sample_aspect_ratio.num, inlink->sample_aspect_ratio.den);

    return 0;
}

static const AVOption setdar_options[] = {
    { "dar", "display aspect ratio", OFFSET(ratio_expr), AV_OPT_TYPE_STRING, { .str = "1" }, .flags = FLAGS },
    { NULL },
};

static const AVClass setdar_class = {
    .class_name = "setdar",
    .item_name  = av_default_item_name,
    .option     = setdar_options,
    .version    = LIBAVUTIL_VERSION_INT,
};

static const AVFilterPad avfilter_vf_setdar_inputs[] = {
    {
        .name             = "default",
        .type             = AVMEDIA_TYPE_VIDEO,
        .config_props     = setdar_config_props,
        .get_video_buffer = ff_null_get_video_buffer,
        .filter_frame     = filter_frame,
    },
    { NULL }
};

static const AVFilterPad avfilter_vf_setdar_outputs[] = {
    {
        .name = "default",
        .type = AVMEDIA_TYPE_VIDEO,
    },
    { NULL }
};

AVFilter ff_vf_setdar = {
    .name      = "setdar",
    .description = NULL_IF_CONFIG_SMALL("Set the frame display aspect ratio."),

    .priv_size = sizeof(AspectContext),
    .priv_class = &setdar_class,

    .inputs    = avfilter_vf_setdar_inputs,

    .outputs   = avfilter_vf_setdar_outputs,
};
#endif /* CONFIG_SETDAR_FILTER */

#if CONFIG_SETSAR_FILTER
/* for setdar filter, convert from frame aspect ratio to pixel aspect ratio */
static int setsar_config_props(AVFilterLink *inlink)
{
    AspectContext *s = inlink->dst->priv;
    int ret;

    if ((ret = get_aspect_ratio(inlink, &s->sar)))
        return ret;

    inlink->sample_aspect_ratio = s->sar;

    return 0;
}

static const AVOption setsar_options[] = {
    { "sar", "sample (pixel) aspect ratio", OFFSET(ratio_expr), AV_OPT_TYPE_STRING, { .str = "1" }, .flags = FLAGS },
    { NULL },
};

static const AVClass setsar_class = {
    .class_name = "setsar",
    .item_name  = av_default_item_name,
    .option     = setsar_options,
    .version    = LIBAVUTIL_VERSION_INT,
};

static const AVFilterPad avfilter_vf_setsar_inputs[] = {
    {
        .name             = "default",
        .type             = AVMEDIA_TYPE_VIDEO,
        .config_props     = setsar_config_props,
        .get_video_buffer = ff_null_get_video_buffer,
        .filter_frame     = filter_frame,
    },
    { NULL }
};

static const AVFilterPad avfilter_vf_setsar_outputs[] = {
    {
        .name = "default",
        .type = AVMEDIA_TYPE_VIDEO,
    },
    { NULL }
};

AVFilter ff_vf_setsar = {
    .name      = "setsar",
    .description = NULL_IF_CONFIG_SMALL("Set the pixel sample aspect ratio."),

    .priv_size = sizeof(AspectContext),
    .priv_class = &setsar_class,

    .inputs    = avfilter_vf_setsar_inputs,

    .outputs   = avfilter_vf_setsar_outputs,
};
#endif /* CONFIG_SETSAR_FILTER */