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

[Ronen Mizrahi]

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
>
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel at mplayerhq.hu
> https://lists.mplayerhq.hu/mailman/listinfo/ffmpeg-devel
>


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
http://www.etsi.org/deliver/etsi_en/300700_300799/300743/01.03.01_60/en_300743v010301p.pdf
)

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.

Best,

Ronen
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 0001-dvb-subtitles-put-the-region-composition-segment-bef.patch
Type: application/octet-stream
Size: 4777 bytes
Desc: not available
URL: <http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/attachments/20110226/3f9f525f/attachment.obj>