PeerStreamer

/*

 * 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

 * null video source

 */

#include "libavutil/avstring.h"

#include "libavutil/eval.h"

#include "libavcore/parseutils.h"

#include "avfilter.h"

static const char *var_names[] = {

    "E",

    "PHI",

    "PI",

    "AVTB",   /* default timebase 1/AV_TIME_BASE */

    NULL

};

enum var_name {

    VAR_E,

    VAR_PHI,

    VAR_PI,

    VAR_AVTB,

    VAR_VARS_NB

};

typedef struct {

    int w, h;

    char tb_expr[256];

    double var_values[VAR_VARS_NB];

} NullContext;

static int init(AVFilterContext *ctx, const char *args, void *opaque)

{

    NullContext *priv = ctx->priv;

    priv->w = 352;

    priv->h = 288;

    av_strlcpy(priv->tb_expr, "AVTB", sizeof(priv->tb_expr));

    if (args)

        sscanf(args, "%d:%d:%255[^:]", &priv->w, &priv->h, priv->tb_expr);

    if (priv->w <= 0 || priv->h <= 0) {

        av_log(ctx, AV_LOG_ERROR, "Non-positive size values are not acceptable.\n");

        return AVERROR(EINVAL);

    }

    return 0;

}

static int config_props(AVFilterLink *outlink)

{

    AVFilterContext *ctx = outlink->src;

    NullContext *priv = ctx->priv;

    AVRational tb;

    int ret;

    double res;

    priv->var_values[VAR_E]    = M_E;

    priv->var_values[VAR_PHI]  = M_PHI;

    priv->var_values[VAR_PI]   = M_PI;

    priv->var_values[VAR_AVTB] = av_q2d(AV_TIME_BASE_Q);

    if ((ret = av_expr_parse_and_eval(&res, priv->tb_expr, var_names, priv->var_values,

                                      NULL, NULL, NULL, NULL, NULL, 0, NULL)) < 0) {

        av_log(ctx, AV_LOG_ERROR, "Invalid expression '%s' for timebase.\n", priv->tb_expr);

        return ret;

    }

    tb = av_d2q(res, INT_MAX);

    if (tb.num <= 0 || tb.den <= 0) {

        av_log(ctx, AV_LOG_ERROR,

               "Invalid non-positive value for the timebase %d/%d.\n",

               tb.num, tb.den);

        return AVERROR(EINVAL);

    }

    outlink->w = priv->w;

    outlink->h = priv->h;

    outlink->time_base = tb;

    av_log(outlink->src, AV_LOG_INFO, "w:%d h:%d tb:%d/%d\n", priv->w, priv->h,

           tb.num, tb.den);

    return 0;

}

static int request_frame(AVFilterLink *link)

{

    return -1;

}

AVFilter avfilter_vsrc_nullsrc = {

    .name        = "nullsrc",

    .description = NULL_IF_CONFIG_SMALL("Null video source, never return images."),

    .init       = init,

    .priv_size = sizeof(NullContext),

    .inputs    = (AVFilterPad[]) {{ .name = NULL}},

    .outputs   = (AVFilterPad[]) {

        {

            .name            = "default",

            .type            = AVMEDIA_TYPE_VIDEO,

            .config_props    = config_props,

            .request_frame   = request_frame,

        },

        { .name = NULL}

    },

};