func: theora_gptopts(AVFormatContext *ctx, int idx, uint64_t gp, int64_t *dts)
  
  {
  
      struct ogg *ogg = ctx->priv_data;
  
      struct ogg_stream *os = ogg->streams + idx;
  
      struct theora_params *thp = os->private;
  
      uint64_t iframe = gp >> thp->gpshift;
  
      uint64_t pframe = gp & thp->gpmask;
  
  
  
      if (thp->version < 0x030201)
  
          iframe++;
  
  
  
      if(!pframe)
  
          os->pflags |= AV_PKT_FLAG_KEY;
  
  
  
      if (dts)
  
          *dts = iframe + pframe;
  
  
  
      return iframe + pframe;
  
  }
  