[Ffmpeg-cvslog] Re: ffmpeg-cvslog Digest, Vol 12, Issue 46

[Steve Lhomme]

> Modified Files:
> 	matroska.c 
> Log Message:
> fixing timebase
> 
> 
> Index: matroska.c
> ===================================================================
> RCS file: /cvsroot/ffmpeg/ffmpeg/libavformat/matroska.c,v
> retrieving revision 1.25
> retrieving revision 1.26
> diff -u -d -r1.25 -r1.26
> --- matroska.c	25 Mar 2006 13:37:34 -0000	1.25
> +++ matroska.c	25 Mar 2006 19:40:27 -0000	1.26
> @@ -2206,7 +2206,7 @@
>              st = av_new_stream(s, track->stream_index);
>              if (st == NULL)
>                  return AVERROR_NOMEM;
> -            av_set_pts_info(st, 24, 1, 1000); /* 24 bit pts in ms */
> +            av_set_pts_info(st, 64, matroska->time_scale, 1000*1000*1000); /* 64 bit pts in ns */
>  
>              st->codec->codec_id = codec_id;
>  
> @@ -2295,7 +2295,7 @@
>              case MATROSKA_ID_BLOCK: {
>                  uint8_t *data, *origdata;
>                  int size;
> -                uint64_t block_time;
> +                int16_t block_time;
>                  uint32_t *lace_size = NULL;
>                  int n, track, flags, laces = 0;
>                  uint64_t num;
> @@ -2329,7 +2329,7 @@
>                  }
>  
>                  /* block_time (relative to cluster time) */
> -                block_time = ((data[0] << 8) | data[1]) * matroska->time_scale;
> +                block_time = (data[0] << 8) | data[1];
>                  data += 2;
>                  size -= 2;
>                  flags = *data;
> @@ -2440,7 +2440,7 @@
>                          pkt->stream_index =
>                              matroska->tracks[track]->stream_index;
>  
> -                        pkt->pts = timecode / 1000000; /* ns to ms */
> +                        pkt->pts = timecode;
>                          pkt->pos= pos;
>  
>                          matroska_queue_packet(matroska, pkt);
> @@ -2514,7 +2514,7 @@
>                  uint64_t num;
>                  if ((res = ebml_read_uint(matroska, &id, &num)) < 0)
>                      break;
> -                cluster_time = num * matroska->time_scale;
> +                cluster_time = num;
>                  break;
>              }

While I assume you have tested this and it works, there is a dangerous 
change in this code. For the moment lavf doesn't handle the "Track 
Timecode Scale" (used to mix audio from 30fps & 25fps with the same 
video) and it's a float. I'm not sure it will fit that new design. You 
might lose some precision when you do :

block_time = ((data[0] << 8) | data[1]) * track->timecode_scale;