[FFmpeg-devel] BUG in use of extradata and extradata_size with dvb subtitles and teletext

Michael Niedermayer michaelni at gmx.at
Wed Jan 8 23:01:34 CET 2014

On Wed, Jan 08, 2014 at 05:33:59PM +0100, Michael Niedermayer wrote:
> On Wed, Jan 08, 2014 at 06:15:19PM +0200, Andriy Lysnevych wrote:
> > Any way we must fix this bug at some point. Having two DVB subtitle formats
> > in FFmpeg already caused a lot of related issues.
> > 
> > Applying only libavcodec change will break DVB subtitle encoder -> MPEG-TS
> > muxer chain and as the result output MPEG-TS stream will contain malformed
> > DVB subtitle payload.
> > 
> > To keep compatibility we can check version of libavformat in DVB subtitle
> > encoder and add beginning 0x00 and trailing 0xFF bytes for older versions
> > as it was before. To do so we must increase version of libavformat with
> > this patch.
> > 
> > Questions are:
> > 1) How to detect libavformat version from libavcodec? Is calling
> > avformat_version() ok?
> no
> libavcodec has no way to detect the libavformat its used with or even
> if its used with any libavformat or different code.
> I think there are only 2 (reasonable) solutions
> A. what ubitux suggested, that a option is added and the default stays
>    the old format and the application would have to set it to have
>    the new format used
> B. just accept that the format was buggy&broken and that this is a bug
>    fix
> Did any application use / depend on this specific "buggy" format ?

> I think ubitux and any application developers affected by this are
> the best to decide of B. is acceptable

and if noone replies then you can probably assume its ok and noone
knows of any code that depends on this format 


Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

You can kill me, but you cannot change the truth.
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