[FFmpeg-devel] DVD subtitles

Erik Slagter erik
Thu Feb 28 11:48:42 CET 2008

>> IMHO it's very easy to make such a filter with the filter example 
>> ("negate") as a basis, although at the moment actually I don't have a 

> Actually, the negate filter read the input frame and put the negated 
> frame in a new frame as output. For a hardsub filter, that would be a 
> needless memcpy. It would be better to use the drawbox filter as a 
> template (yes, it is not even in the SoC tree yet, I'll put it there soon).

Point taken.

> For doing this you should modify the avfilter framework to filter also 
> subtitles (now, it only work for video but subtitle and audio is planned 
> for the future). It means making CODEC_TYPE_SUBTITLE as a valid value 
> for AVFilterPad.type while keeping the framework sane. That will be the 
> hardest part. Then you can make a filter that has one video stream and 
> one subtitle stream as input and one video stream as output.

So what you're saying is that the correct approach would be to have a 
filter with two input "pads", a video input and a subtitle input. Hmmm, 
looks logical to me, indeed.

Anyway, for the moment I am using a some q&d tricks to achieve my goal, 
but if libav* is up for it and you're available to point me in the right 
direction, I'd take on the challenge.

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