FFmpeg/libavfilter/vf_settb.c

/*
 * Copyright (c) 2010 Stefano Sabatini
 *
 * 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
 */

/**
 * @file
 * Set timebase for the output link.
 */

#include "libavutil/avstring.h"
#include "libavutil/eval.h"
#include "libavutil/mathematics.h"
#include "libavutil/rational.h"
#include "avfilter.h"
#include "internal.h"

static const char *var_names[] = {
    "AVTB",   /* default timebase 1/AV_TIME_BASE */
    "intb",   /* input timebase */
    NULL
};

enum var_name {
    VAR_AVTB,
    VAR_INTB,
    VAR_VARS_NB
};

typedef struct {
    char tb_expr[256];
    double var_values[VAR_VARS_NB];
} SetTBContext;

static av_cold int init(AVFilterContext *ctx, const char *args, void *opaque)
{
    SetTBContext *settb = ctx->priv;
    av_strlcpy(settb->tb_expr, "intb", sizeof(settb->tb_expr));

    if (args)
        sscanf(args, "%255[^:]", settb->tb_expr);

    return 0;
}

static int config_output_props(AVFilterLink *outlink)
{
    AVFilterContext *ctx = outlink->src;
    SetTBContext *settb = ctx->priv;
    AVFilterLink *inlink = ctx->inputs[0];
    AVRational time_base;
    int ret;
    double res;

    settb->var_values[VAR_AVTB] = av_q2d(AV_TIME_BASE_Q);
    settb->var_values[VAR_INTB] = av_q2d(inlink->time_base);

    outlink->w = inlink->w;
    outlink->h = inlink->h;

    if ((ret = av_expr_parse_and_eval(&res, settb->tb_expr, var_names, settb->var_values,
                                      NULL, NULL, NULL, NULL, NULL, 0, NULL)) < 0) {
        av_log(ctx, AV_LOG_ERROR, "Invalid expression '%s' for timebase.\n", settb->tb_expr);
        return ret;
    }
    time_base = av_d2q(res, INT_MAX);
    if (time_base.num <= 0 || time_base.den <= 0) {
        av_log(ctx, AV_LOG_ERROR,
               "Invalid non-positive values for the timebase num:%d or den:%d.\n",
               time_base.num, time_base.den);
        return AVERROR(EINVAL);
    }

    outlink->time_base = time_base;
    av_log(outlink->src, AV_LOG_INFO, "tb:%d/%d -> tb:%d/%d\n",
           inlink ->time_base.num, inlink ->time_base.den,
           outlink->time_base.num, outlink->time_base.den);

    return 0;
}

static void start_frame(AVFilterLink *inlink, AVFilterBufferRef *picref)
{
    AVFilterContext *ctx = inlink->dst;
    AVFilterLink *outlink = ctx->outputs[0];
    AVFilterBufferRef *picref2 = picref;

    if (av_cmp_q(inlink->time_base, outlink->time_base)) {
        picref2 = avfilter_ref_buffer(picref, ~0);
        picref2->pts = av_rescale_q(picref->pts, inlink->time_base, outlink->time_base);
        av_log(ctx, AV_LOG_DEBUG, "tb:%d/%d pts:%"PRId64" -> tb:%d/%d pts:%"PRId64"\n",
               inlink ->time_base.num, inlink ->time_base.den, picref ->pts,
               outlink->time_base.num, outlink->time_base.den, picref2->pts);
        avfilter_unref_buffer(picref);
    }

    avfilter_start_frame(outlink, picref2);
}

AVFilter avfilter_vf_settb = {
    .name      = "settb",
    .description = NULL_IF_CONFIG_SMALL("Set timebase for the output link."),
    .init      = init,

    .priv_size = sizeof(SetTBContext),

    .inputs    = (AVFilterPad[]) {{ .name             = "default",
                                    .type             = AVMEDIA_TYPE_VIDEO,
                                    .get_video_buffer = avfilter_null_get_video_buffer,
                                    .start_frame      = start_frame,
                                    .end_frame        = avfilter_null_end_frame },
                                  { .name = NULL }},

    .outputs   = (AVFilterPad[]) {{ .name            = "default",
                                    .type            = AVMEDIA_TYPE_VIDEO,
                                    .config_props    = config_output_props, },
                                  { .name = NULL}},
};