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

Stefano Sabatini stefasab at gmail.com
Sun Sep 25 17:52:10 CEST 2011


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

* fix rendering
* YUV and more RGB formats support
* optimizations?

The problem with the weird rendering which I observe possibly depends
on the fact that libass doesn't automatically select the Default
style, if not specified explicitely on the dialog lines.

I got the test file converting an SRT to ASS using ffmpeg (and got no
Style in the dialog lines), so maybe this is a problem which should be
fixed in the conversion code.

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.
FFmpeg = Forgiving and Fabulous Meaningful Power Exuberant Ghost
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