[FFmpeg-devel] [PATCH] libavformat: libavformat: output cues for each subtitle block in MKV muxer

[wm4]

On Sun, 25 May 2014 10:05:24 -0400
John Peebles <johnpeeb at gmail.com> wrote:

> > This patch doesn't apply on FFmpeg git master.
> The new version attached should apply.
> 
> > please do not include re-indent change into the patch
> done
> 
> > Can you also provide a sample and command line to reproduce?
> Sure.
> (1) Download the attached same-time-script.mkv file. Note that while
> this file only contains a subtitle track in order to keep the file size
> down,
> the bug still happens even if there are other tracks.
> (2) Run ffmpeg -i same-time-script.ass -c copy -map 0 bad.mkv
> (3) Inspect the ebml data in bad.mkv. Notice that while there are two
> subtitle blocks (one for each of two different subtitles), there is only a
> CueTrackPositions element for the first block. There should be one for
> each block.
> 
> > Is the issue you are fixing the same as ticket #3149?
> No, this patch only deals with cues for subtitle tracks, not audio tracks.
> 

Are you sure this is how it's supposed to work? The sample file you
posted has two cue entries for the same time. I think it should have
only 1 entry, pointing to the first packet. Is it documented somewhere
how this should work? (I know it's not in the "specification".) The
fact that your sample was apparently produced by mkvmerge doesn't say
much; redundant cues are probably ok, but the question is whether
they're "needed".