[FFmpeg-devel] Subtitle filters in libavfilter

[Marcus Johnson]

Blu-rays use PGS subs, which are bmps why can't you render directly?


On Tue, Jan 29, 2013 at 4:42 PM, Chris Burel <chrisburel at gmail.com> wrote:

> Hi,
> A while ago, I wrote about trying to add support for rendering text-based
> subtitles.  What I'm trying to achieve is to support transcoding .ass
> subtitles to xsub, to stream to the PS3.
>
> I saw recently that some new video filters had been added, one called "ass"
> and one called "subtitle", for hard-coding the subtitles into the video
> stream.  These filters were implemented as video filters.  I started
> looking at the code, and it seems like most of the code could be reused if
> there were a bit more division of labor.  I'd like to see one filter for
> rendering text subtitles to images, that would output a subtitle stream,
> and a separate filter that would hard-code those subtitles on top of a
> video stream.  That way, all the code for rendering the subtitles could be
> used for transcoding them to any image-based subtitle format.
>
> I started looking at adding subtitle support to libavfilter, but I got
> bogged down in bits that I don't see how they apply to a subtitle stream,
> like the query_formats() function.  Is there someone that could help me
> write a null subtitle filter, to see what all the necessary parts are?
>
> Thanks,
> Chris
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