[FFmpeg-devel] [PATCH] attachments support in matroska demuxer

Alexander Strange astrange
Thu Jan 3 03:06:58 CET 2008

On Jan 2, 2008, at 8:45 PM, Loren Merritt wrote:

> On Wed, 2 Jan 2008, Rich Felker wrote:
>> On Wed, Jan 02, 2008 at 06:49:28AM +0200, Uoti Urpala wrote:
>>> Extradata may happen to be identical, but subtitles can refer to  
>>> "the
>>> same font" in a stricter sense. If you demux a .mkv file into  
>>> separate
>>> files, a natural format is to have an audio file (or files), a video
>>> file, a .ssa/.ass file (or files) and a bunch of font files. Nobody
>>> splits video/audio tracks into separate "standard extradata" and  
>>> "main
>>> content" parts.
>> I agree here too. Most subtitle 'codecs' already have an extradata
>> format of their own, text-based, separate from the binary ttf data.
>> Most likely it's the "header text" which would appear at the  
>> beginning
>> of the subtitle file if it were flat text. So it would be rather
>> problematic to try to munge the fonts together with this...
> You can put fonts in SSA extradata, using a variant of uuencoding. I
> haven't seen this recently, but I have some movies using this from  
> before
> matroska.
> --Loren Merritt

This usually isn't done in practice, although it might be useful for  
mkvmerge will actually delete Font sections and add them as new mkv
attachments. Anyway, since Unicode fonts can be several MB, I really
wouldn't want them ending up in text files I want to edit.

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