[FFmpeg-devel] [PATCH] extractplanes filter

Nicolas George nicolas.george at normalesup.org
Mon May 6 14:31:56 CEST 2013

Le septidi 17 floréal, an CCXXI, Nicolas George a écrit :
> I managed to reproduce it, I will investigate.

Understood. There is a bug in the format negotiation loop that counts EAGAIN
for success, and therefore runs the loop again with an identical graph. I
have a patch for that that is currently running fate.

> > Current one works more/less by pure luck, for example: rgb24 is only
> > input of inlnik and than gbrp get picked out for outlinks.
> This one I did not manage to reproduce.

This one is more tricky.

The basic reason is that extractplanes does not support rgb24.

If you set the supported input formats before returning EAGAIN, then lavfi
will need to insert a convert filter. On the next round, extractplanes will
see all the output formats supported by the convert filted, including RGB
and YUV formats, and will not be able to decide (the user will get an error
message asking for the format filter to set formats).

If you set the supported input formats only once you know the kind of input
format you have to handle, then the same convert filter will be inserted,
but then lavfi could select a completely different format as input to
extractplanes. Fortunately, lavfi seems smart enough to favour formats that
need less conversion.

I had not anticipated that tricky situation because I only had simpler
inputs to deal with until now. I believe I can get it working, but I will
need some time for that. The basic idea would be to set the input formats
according to the ones available on the other side of the link.


  Nicolas George
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