[FFmpeg-devel] lavfi state of affairs 2

[Stefano Sabatini]

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.

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).

Regards.
-- 
FFmpeg = Faithless & Friendly Mastodontic Powerful Enchanting God