[FFmpeg-devel] [WIP] libass subtitle renderer filter

Baptiste Coudurier baptiste.coudurier at gmail.com
Mon Sep 26 01:20:59 CEST 2011

On 9/25/11 8:52 AM, Stefano Sabatini wrote:
> Hi,
> as in $subject, usage:
> $ ffplay -vf "ass=ff=FreeSerif.ttf:f=SUB.ass" FILE 
> This has still problems, maybe something's wrong with how I'm using
> libass (on the other hand both libass and the ASS format itself are
> painfully under-specificated so it's not easy to figure out what's
> wrong).
> Todo:
> * fix rendering

What's wrong with rendering ?

> [...]
> YUV path is partly addressed in a patch I got from Baptiste (from the
> other points of view his variant is more or less equivalent to this
> one, but my code is funnier to read due to the AssContext).
> Note that I don't want to make a generic subtitles renderer of this,
> but just a simple wrapper around libass.
> A more generic subtitle renderer should be done relying on
> libavcodec/libavformat, and writing an internal AVSubtitle to video
> renderer engine.

There are 2 situations: internal subtitle streams and external subtitle
Also, I don't think using AVSubtitle for text based subtitles is worth it.
I was more thinking of a generic vf_sub.c subtitle renderer filter,
similar to sub.c in mplayer, that handles all kind of subtitles files.

For internal picture subtitle streams, another filter can decode the
stream to AVSubtitle and burn the picture, maybe the 2 filters can be


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