[FFmpeg-devel] On libavfilter: A Summary of Issues

Derek Buitenhuis derek.buitenhuis at gmail.com
Sun Oct 7 21:03:37 CEST 2012

On 07/10/2012 2:37 PM, Michael Niedermayer wrote:
> why would you want to use linux?
> now that question is stupid but so is yours.

This is a flawed analogy. Using Linux has many technical merits over
other kernels. Using lavfi's C API has no technical merits over
any other framework, only shortcomings. If you can point out any,
please feel free to.

> You have posted a list of shortcommings of libavfilter and we would
> like to improve things, adding the ability to load *synth filters
> to libavfilter removes a large part of the problems you listed.
> I understand that you prefer that libavfilter is removed and replaced
> by vapoursynth but vapoursynth is not a replacement for it, it lacks
> quiet a few things currently and we do not know if it ever will be a
> replacement.

I may have been unclear. I don't think lavfi should be remove. I think
people should rethink its goal and use-case. As a library to help with
common things like cropping and stuff, while conveniently being located
within ffmpeg, I think it's fine. It's also fine to simplify and make
the logic in e.g. ffmpeg.c nicer. What I take issue with is pushing
for a use-case in which other apps use it as a filtering framework
(e.g. handbrake). It makes no sense with that use-case.

> So please lets try to move forward and improve, if you want to add
> a filter framework as a demuxer,
> sure go ahead. It certainly will have its users.
> But libavfilter also has its users and at least i would like to
> have the ability to use *synth filters, *synth scripts and all that
> from it. if you want to implement that for us, it certainly would
> make me happy and i think other people who work on libavfilter too.
> You know vapoursynth so you are quite qualified to do it, but if you
> dont want to, someone else should.

To be clear, I am writing a demuxer for VapourSynth -scripts-. These
scripts return video. It makes sense to do it as a demuxer. Same
as our Avisynth demuxer. Loading VapourSynth plugins is an entirely
different story and use-case, and yes, -that- would belong in
lavfi. But that's not what I'm writing.

- Derek

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