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

JULIAN GARDNER joolzg at btinternet.com
Thu Apr 14 10:27:09 CEST 2011

--- On Thu, 14/4/11, Tomas Härdin <tomas.hardin at codemill.se> wrote:

> From: Tomas Härdin <tomas.hardin at codemill.se>
> Subject: Re: [FFmpeg-devel] DVB Subtitles - "Hard Subtitles"
> To: "FFmpeg development discussions and patches" <ffmpeg-devel at ffmpeg.org>
> Date: Thursday, 14 April, 2011, 8:31
> 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..
> /Tomas

Thanks for the pointers, i was looking at the "drawtext" filter and thinking the same, us this system.

I will do a couple of tests and see if i can find the problems in the encoded subtiles.


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