[FFmpeg-devel] DVB Subtitles

JULIAN GARDNER joolzg at btinternet.com
Mon Jun 11 19:40:16 CEST 2012

> From: Wolfram Gloger <wmglo at dent.med.uni-muenchen.de>
>To: FFmpeg development discussions and patches <ffmpeg-devel at ffmpeg.org> 
>Sent: Monday, 11 June 2012, 18:30
>Subject: Re: [FFmpeg-devel] DVB Subtitles
>JULIAN GARDNER <joolzg at btinternet.com> writes:
>>> From: Michael Niedermayer <michaelni at gmx.at>
>>>Some "subtitles" may be present for 2 hours but the packets likely
>>>get repeated at intervals shorter than 20 seconds otherwise one could
>>>not start playback of such a stream from the middle. And i find even
>>>20seconds unlikely long for that. That would implicate if one tuned
>>>to a channel and started watching the channel logo would be missing
>>>for 20 seconds in some cases
>> hmm does not matter Micheal as long as the epoch does not change and
>> the end_time is correct every packet will say Start at 0 end at 120,
>> if you join in the middle you will still get the 1st epoch and as your
>> in the stream you will show it until 2 hours from the start.
>Hmm, so the times are somehow absolute?  Interesting,
>but basically you have confirmed Michael's point as there are
>regular packets in the subtitle stream even for such a 2-hour
>title.  The problem case we were discussing was when there would
>be _no packet at all_ for such a long time and only then the
>latency/memory usage issue would occur.
>ffmpeg-devel mailing list
>ffmpeg-devel at ffmpeg.org
Does not comfirm Micheal policy, it all depends on the epoch and the end time, 1 subtitle sent every 30 seconds, and all will have the same endtime, so at the start it finishes at X pts, in the middle it will be X pts near the end it will be X pts

Now the end time is not an end time per se, its is really a clear display as i have already said. The way it works is as follows

New Subs comes in with new EPOCH and shows subtitles, end time set to be 30 seconds in the future.
Subs finish with an EPOCH with no regions, so we clear the display.

Now if the last subs is missed for some reason then the end time will come into play and clear the display after 30 seconds, this will fix the case you mentioned.


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