[FFmpeg-devel] [PATCH] timestamp discontinuity in subtitles is OK

[Michael Niedermayer]

On Thu, Oct 09, 2008 at 12:39:21AM +0200, Aurelien Jacobs wrote:
> Michael Niedermayer wrote:
> 
> > On Mon, Oct 06, 2008 at 08:24:45AM -0000, Wolfram Gloger wrote:
> > > Hi,
> > > 
> > > > i think there is a easier solution
> > > > just check for AVFMT_TS_DISCONT which would prevent misdetection in all
> > > > containers that do not allow discontinuities.
> > > 
> > > But we _do_ have containers with AVFMT_TS_DISCONT which can have
> > > subtitles in them (dvbsub in mpegts, dvdsub in mpeg), so this wouldn't
> > > help.
> > 
> > when discontinuities are allowed, then they likely are also allowed
> > between subtitle packets (but if you disagree, feel free to quote the specs,
> > id be happy to hear what they say ...),
> > thus whichever way is used to detect them, the detection should
> > be needed between subtitle packets as well.
> > 
> > a check for AVFMT_TS_DISCONT is correct, one for subtitles is not AFAICS.
> > The real question is what do the dvbsub/dvdsub specs say about
> > discontinuities?
> 
> I guess attached patch is what you meant.
> 
> Aurel
> Index: ffmpeg.c
> ===================================================================
> --- ffmpeg.c	(revision 15588)
> +++ ffmpeg.c	(working copy)
> @@ -285,6 +285,7 @@
>                                  is not defined */
>      int64_t       pts;       /* current pts */
>      int is_start;            /* is 1 at the start and after a discontinuity */
> +    int ts_discont;
>  } AVInputStream;
>  
>  typedef struct AVInputFile {
> @@ -1573,6 +1574,7 @@
>                  ist->start = av_gettime();
>                  ist->frame = 0;
>              }
> +            ist->ts_discont = is->iformat->flags & AVFMT_TS_DISCONT;
>          }
>      }
>  

> @@ -2105,7 +2107,8 @@
>          }
>  
>  //        fprintf(stderr, "next:%"PRId64" dts:%"PRId64" off:%"PRId64" %d\n", ist->next_pts, pkt.dts, input_files_ts_offset[ist->file_index], ist->st->codec->codec_type);
> -        if (pkt.dts != AV_NOPTS_VALUE && ist->next_pts != AV_NOPTS_VALUE) {
> +        if (pkt.dts != AV_NOPTS_VALUE && ist->next_pts != AV_NOPTS_VALUE
> +            && ist->ts_discont) {
>              int64_t pkt_dts= av_rescale_q(pkt.dts, ist->st->time_base, AV_TIME_BASE_Q);

Is there any reason why is->iformat->flags & AVFMT_TS_DISCONT is not
directly used here?

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

When the tyrant has disposed of foreign enemies by conquest or treaty, and
there is nothing more to fear from them, then he is always stirring up
some war or other, in order that the people may require a leader. -- Plato
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