[FFmpeg-devel] [PATCH 1/2] matroskaenc: Add CuePoints for subtitle tracks

James Almer jamrial at gmail.com
Fri Sep 20 01:21:16 CEST 2013

On 19/09/13 7:11 PM, Michael Niedermayer wrote:
> On Sat, Sep 14, 2013 at 05:59:21AM -0300, James Almer wrote:
>> Signed-off-by: James Almer <jamrial at gmail.com>
>> ---
>>  libavformat/matroskaenc.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
> Do these 2 patches fix/improve playback/seeking with some software?
> If so please put this information in the commit message
> and also explain how the issue and fix can be reproduced if you
> have a testcase

I don't know if any software currently reads and uses cues for subtitle tracks, 
and considering how new the cueduration element is i doubt any software reads 
them either.
I'm essentially replicating mkvtoolnix muxing practices with this. Afaik, with 
proper demuxer/splitter support, the idea of having a cueduration entry in 
subtitle cue points is to improve the display of subtitles right after seeking 
to a given point in the stream.

While we're at it, another (unrelated) patch i intended to submit was one to 
add cues to audio streams, which should hopefully improve seeking with most 
if not all software with audio only files as we currently only write cues for 
video tracks, but I need suggestions about what criteria to use to add the 
One option is making one per cluster, but they can be as long as five seconds 
each. One per block is certainly not a good option since they can be as small 
as a few milliseconds each, which would mean hundreds of cue points even with 
small files.
Another option is making a new cluster every two seconds instead of five 
when muxing mka files, but i want opinions before doing anything like that.


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