[FFmpeg-devel] [RFC] libavfilter-soc and variable-frame-size video streams

Michael Niedermayer michaelni
Sat Dec 13 14:23:40 CET 2008

On Fri, Dec 12, 2008 at 04:54:26PM -0800, Jason Garrett-Glaser wrote:
> > But maybe I'm just confused and there is a far simpler solution, or
> > maybe we could just decide that supporting variable-frame-size video
> > streams is not worth that hassle.
> This sounds reasonable to me: thinking through what every filter would
> have to do to support such a thing, it sounds completely
> unmaintainable, especially for filters that act temporally: how will
> they deal with the fact that cached temporal data from previous frames
> (such as for temporal denoisers) is no longer the correct size
> matching the current frame?!
> Avisynth gets away just fine without variable frame size support: I
> have actually never seen such a thing as a feature request either.  I
> don't think libavfilter needs it either.

I think variable size is pretty much a requirement for libavfilter.
I dont remember exactly how/if this was discussed during lavfi development
but it surly is not ok to drop it. Also lack of support of it in Avisynth
is not an argument not to support it in lavfi.

About individual filters, variable size support is surely optional and
that way its no burden on a per filter level.

Filters that are "stateless" should be able to very easily support it,
the scale filter has to support it for the obvious reason to remove
size changes at the begin of a filter chain when that is wanted.
and temporal filters may or may not be able to easily support it, after
all they dont have to do much more than free their stuff and pretend its
the start of a stream.


Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Many things microsoft did are stupid, but not doing something just because
microsoft did it is even more stupid. If everything ms did were stupid they
would be bankrupt already.
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