[FFmpeg-devel] DVB Subtitles - "Hard Subtitles"

Tomas Härdin tomas.hardin at codemill.se
Thu Apr 14 09:31:55 CEST 2011

JULIAN GARDNER skrev 2011-04-13 18:31:
> Right been fighting with getting ffmpeg to add in a DVB Subtitle stream, ive used '-scodec copy' and '-scodec dvbsub' but to no avail.

dvbsub remuxing is known to be broken, at least for mpegts.
I looked into this earlier, and it's basically a few header bytes that 
the decoder, encoder, muxer and demuxer disagree on how to handle.

If you search the archive you'll probably find my thread on the matter. 
I didn't bother finishing it up as it was work related and other things 
popped up.

Basically, look at what the dvbsub decoder expects, what the encoder 
outputs and what the mpegts muxer writes. IIRC the muxer writes header 
bytes the decoder expects instead of the encoder outputing them.

> So now im looking at modifying the code to do "Hard Subtitles" so i was wondering whats the best way and some pointers as to where i can break into the demux->decode->resize->encode->remux so that we we do it as demux->decode->"Hard subs"->resize->encode->remux.

I think one could extend the overlay filter to take subtitle rects. 
lavfi barely has support for audio though, let alone subtitles..


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