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

Clément Bœsch ubitux at gmail.com
Wed Oct 5 08:16:15 CEST 2011

On Sun, Sep 25, 2011 at 05:52:10PM +0200, Stefano Sabatini wrote:
> Hi,
> as in $subject, usage:
> $ ffplay -vf "ass=ff=FreeSerif.ttf:f=SUB.ass" FILE 

Are the internal fonts set in the ASS file loaded?

> 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
> * 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).

ASSContext sounds better to me :)

> Note that I don't want to make a generic subtitles renderer of this,
> but just a simple wrapper around libass.

Being able to burn some crazy subtitles like
http://www.youtube.com/watch?v=dacAu3i3864 in FFmpeg with such filter is
really great, thank you both for writing this filter.

> A more generic subtitle renderer should be done relying on
> libavcodec/libavformat, and writing an internal AVSubtitle to video
> renderer engine.

There is indeed places for improvement here, and I'd like to help

Clément B.
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