[FFmpeg-devel] [PATCH] Bluray Subtitle Support, v7 (Updated patch to v12)

[Ian Caulfield]

2009/8/26 Carl Eugen Hoyos <cehoyos at ag.or.at>:
> Reimar D?ffinger <Reimar.Doeffinger <at> gmx.de> writes:
>
>>
>> On Wed, Aug 26, 2009 at 11:00:52AM +0200, Reimar D?ffinger wrote:
>> > When muxing into AVI for xsub I first get a crash, and after fixing that
>> > I get "scale/rate is 0/1 which is invalid. (This file has been generated by
>> > broken software.)" when trying to play the result.
>>
>> Ok, I have a couple of issue with the AVI demuxer and other stuff.
>> The first one is that the time base of subtitle streams stays at
>> the default of 90 kHz, which is a bit questionable but probably
>> acceptable.
>> The second and bigger one is that the avi muxer uses the (completely
>> undocumented btw.) ff_parse_specific_params which seems to guess a time
>> base.
>> The issue with this is that for this it uses the codec values and only
>> those, which are never set for subtitles, overwriting the perfectly
>> good values from the stream time base. WTF?
>> Later this causes a crash due to a division by 0 when rescaling the
>> subtitle time base to the now broken stream time base.
>> This "fixes" it, but I have no idea if it makes anything actually work:
>
> With the patch, subtitles are actually encoded (file size 10 times bigger), but
> nothing is shown on playback: Perhaps because of these messages while encoding:
> [xsub @ 0x141e450]No more than 4 subtitle colors supported (256 found.)
> ? ?Last message repeated 6 times
>
> With -scodec dvdsub, I now get
> dvd_subtitle too big
> Subtitle encoding failed
> and encoding stops before anything was actually written to the file (after
> processing 1000 frames).
> If I raise the subtitle_out_max_size in ffmpeg.c, I get warnings about "buffer
> underflow" and "packet too large, ignoring buffer limits to mux it", final file
> size is slightly bigger, but I cannot see subtitles when playing the file with
> ffplay or mplayer.
>

There's probably the issue that Blu-Ray subtitles support much larger
picture areas and more colours than DVD subtitles (otherwise DVD
subtitles could have been re-used), and so won't encode nicely... it
might be worth trying the dvbsub encoder - that might support 256
colours.

Ian