[FFmpeg-devel] lavfi state of affairs 2

[Vitor Sessak]

Stefano Sabatini wrote:
> Hi all,
> 
> this has to be meant as the follow-up of
> http://thread.gmane.org/gmane.comp.video.ffmpeg.devel/81034/
> 
> Since then regressions has been fixed, works on alpha blending support
> has been committed to libswscale (a quite important feature for lavfi
> I think) and VHOOK has been removed from FFmpeg, so people is going fo
> get puzzled since they can't find it anymore, and is starting to use
> lavfi more and more (getting puzzled again for its lack of
> documentation ... :-|).
> 
> But this is also a good thing for lavfi since more and more people is
> getting aware of it and starting to use and test it.
> 
> I'll try to resume here the main current issues.
> 
> * Expand filter missing.
> 
>   There is the need for an expand filter with "direct rendering", that
>   is which doens't require memcpy of any sort, this maybe requires API
>   extension:
>   http://thread.gmane.org/gmane.comp.video.ffmpeg.devel/85015
> 
>   MPlayer already has such a thing, so it may be worthwhile check that
>   code, in general is a good idea to check out all the filters in
>   MPlayer/libmpcodecs in order to avoid to waste time reinventing the
>   wheel.
> 
>   Same considerations apply for the syntax, when possible is a good
>   idea to keep the same syntax (when sane) of the corresponding
>   MPlayer filters.
> 
>   An implementation of an expand/pad filters has been already posted
>   on the soc ML:
>   http://thread.gmane.org/gmane.comp.video.ffmpeg.soc/2779/
> 
> * vf_scale filter missing
>   This has to have the same features as the MPlayer's one, this should
>   be trivial.
>   See again:
>   http://thread.gmane.org/gmane.comp.video.ffmpeg.devel/85015
> 
> * A more powerful system for dealing with image formats is needed to
>   avoid bad code duplication. I mean some system to tell if a format
>   is for example packed, planar, the number of channels/planes and so
>   on, as discussed here:
>   http://thread.gmane.org/gmane.comp.video.ffmpeg.devel/83733
> 
>   and creates corresponding AVFilterFormats lists.
> 
>   pixdesc.[ch] already committed in SVVN may provide the foundations
>   for such a system (I intend to work on this).
> 
> * Maybe a one-pixel colorspace transform, as discussed here:
>   http://thread.gmane.org/gmane.comp.video.ffmpeg.soc/5727/focus=5739
> 
>   may avoid code duplication for all that filters that need to execute
>   YUV <-> RGB or some other transformation just for one color.
> 
>   I'm not sure what's the better place for it, but lsws seems the
>   obvious choice.
> 
> * More documentation for the various filters, so that people don't
>   need for example to read the code in order to understand how to use
>   the various filters. Ideally the filters should be auto-documented,
>   (for example they should support an help options), but for starting
>   a simple texinfo page for them may be sufficient.

I'd like to add also to add

* Rework ffplay.c patch to be more similar to the ffmpeg.c one, notably 
using vf_buffer.c

> So please consider to work on it if you like to see lavfi integrated
> into SVN soon, also many things could be nice qualification tasks for
> GSOC students (for example porting existing filters to lavfi).

Talking about GSoC, what is your opinion about this: 
http://wiki.multimedia.cx/index.php?title=Talk:FFmpeg_Summer_Of_Code_2009#Libavfilter_work_.2B_audio_support 
?

-Vitor