[mythtv] Fwd: DVB subtitles and delay

Kenni Lund kenni at kelu.dk
Mon Apr 19 22:13:48 UTC 2010


2010/4/19 Janne Grunau <janne-mythtv at grunau.be>:
> On Fri, Apr 16, 2010 at 07:19:07PM +0200, Kenni Lund wrote:
>> 2010/4/14 Mark Kendall <mark.kendall at gmail.com>:
>> >
>> > For what it's worth, I spent some time looking at that ticket a few
>> > weeks ago without much success.
>> >
>> > The problem lies somewhere between the broadcaster and ffmpeg's
>> > demuxing of the stream,
>
> or our own modifications
>
>> > with the net result that some subtitles arrive
>> > very late. I worked with the patch that Janneg posted to the ticket
>> > for queueing transmitted packets and that did generate some
>> > improvements but it certainly did not fix it and was far from a
>> > complete/commitable solution.
>
> yes, it started as proof of concept and was unfortunately much harder
> than thought.
>
>> > There are various issues - though
>> > ideally this would be fixed within ffmpeg itself. Overall there is no
>> > simple fix that I can see that sits within the main MythTV code.
>>
>> Mark, FYI it seems like the issue have been fixed in upstream FFMPEG.
>> I tested the clip from ticket #6753 with ffplay from FFMPEG SVN r22837
>> and AFAICT the subtitles are perfectly in sync, unlike in 0.23-fixes
>> or trunk.
>
> no, ffplay has queues for audio, video and subtitle streams. It was the
> inspiration for my patch.

Janne, thank you for the explanation. I'm sorry to hear that this was
not a FFMPEG issue after all :-/

Please tell if we, as users, can do anything to help moving this
forward. We're quite a few people who have no way of getting a fully
working MythTV system, as 0.21, 0.22, 0.23 all have various issues
with DVB playback and/or DVB subtitles (0.21-fixes=playback
stuttering, 0.22-fixes=no subtitles, 0.23-fixes=subtitles
out-of-sync). This issue is the last remaining one, which once solved,
should allow us to use DVB again.

Thanks
Kenni


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