[Ffmpeg-devel] Video Filter Layer (was: Re: Cropping / Paddingpatches)

Luca Abeni lucabe72
Wed Mar 15 16:26:51 CET 2006

Hi Michael,

On Wed, 2006-03-15 at 14:24 +0100, Michael Niedermayer wrote:
> I missed the discussion about it. Where can
> > I find some references?
> mails by rich/arpi/ivan/... on mp-devel(-g2?) with video filter or so in
> the subject i guess
Ok, thanks for the pointer. I did not know about G2... I had a look at
the mailing list archives, and I understand this is a hot topic :)
Judjing from the various threads I found there, designing and
implementing the video filter layer will be a loooooooooooooong
thing... :(

> > I am interested in this stuff to integrate swscaler.
> > But I fear that if I do the swscaler integration in the wrong way (for
> > example, without using a proper video filter layer) working on it could
> > be useless. So, I want to do it the right way.
> well, iam unsure ..., a video filter layer would be nice but this is alot
> of work, and i fear that the swscaler integration might be delayd very
> significantly if we want a finished video filter layer first
Now I agree with you :)

> so maybe its better to implement it without a vf layer first and work
> on vf after that
Ok... So, here is my new re-revised plan:
1) adjust ffmpeg cropping and padding code so that swscaler integration
is easier (the patches I posted some days ago should be fine, I think...
I'll fix the bug found by Baptiste and repost them). This will be done
without libavfilter.
2) test external swscaler. In the meanwhile, I'll study the filter
discussions happened on the G2 mailing list, to better understand how
the filter layer should be organized
3) integrate swscaler. In the meanwhile, start a discussion on the
mailing list for designing the new filter layer
4) figure out the license problem
5) if the swscaler license situation is acceptable, remove the "old"
ffmpeg rescaling routines. Otherwise, the two implementation will
coexist in ffmpeg
6) At this point, the discussion about the new filter layer should be
completed, and we should have a design (am I being to optimistic?)
7) Implement the video filter layer, and move all the cropping, padding,
and rescaling code to it.

> personally, i would strongly suggest to implement a vf layer incrementally
> so for example completely ignore slices first and only after the vf layer is
> working try to add slice based rendering
After reading some of the G2-related emails, I agree :)
In my opinion, the first implementation of the video filter layer will
not support slices

Thanks again for all the explainations and the feedback

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