/*
  * 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 "libavutil/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}
     },
 };