[FFmpeg-devel] Another possible bug in dvbsub.c

Ronen Mizrahi ronen
Sat Feb 26 20:56:26 CET 2011

On Wed, Feb 16, 2011 at 2:50 AM, Tomas H?rdin <tomas.hardin at codemill.se>wrote:

> Ronen Mizrahi skrev 2011-02-16 03:05:
>  On Sat, Feb 12, 2011 at 5:27 PM, Ronen Mizrahi<ronen at tversity.com>
>>  wrote:
>>  Hello,
>>> The problem with current dvbsub encoded with ffmpeg is that the subtitles
>>> are not remove from display as expected (they remain displayed for a much
>>> longer period, unless some other sub replaces them). This was tested with
>>> VLC, ffplay, and also with other hardware devices (set-top-boxes).
>>> By comparing to VLC code base (
>>> http://git.videolan.org/?p=vlc.git;a=blob;f=modules/codec/dvbsub.c;h=432f9b0bb18ee300080af6a30a1fc8648cae7492;hb=HEAD
>>> )
>>> we were able to make a small change that seem to have fixed the
>>> problem: when hide_state is TRUE, no region related information should be
>>> written. This is unlike the current code where it does write the region
>>> ids
>>> and their x,y position, as well as some other information.
>>> Since I am not a dvbsub expert and since the spec is not very clear with
>>> regard to this situation I wanted to see if someone on the list can
>>> confirm
>>> this correction. If so, I am happy to submit a patch.
>>> Best,
>>> Ronen
>>>  Any feedback from someone on the list? Would you consider a patch?
> Well, it's hard to comment on patches that aren't attached :)  Also, if it
> fixes the subs for a lot of players as well as STBs, then ovbiously such a
> patch is of interest.
> /Tomas
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Please see attached a patch for dvbsub.c with the following changes:
- Do not output any region related data when in hide state (fixes issues
with subtitles not being removed from screen when they expire)
- Put the region composition segment before the clut (as required by the
standard - see

With these fixes we can confirm that dvb subtitles encoded by ffmpeg seem to
work correctly with VLC, ffplay and several set-top-boxes we tested.


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