[FFmpeg-devel] [PATCH] extractplanes filter

[Paul B Mahol]

On 5/6/13, Nicolas George <nicolas.george at normalesup.org> wrote:
> Le septidi 17 floreal, an CCXXI, Nicolas George a ecrit :
>> 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.

You mean from format negotiation side, and not from filter side?

Less code/work to do in filter - less bugs - better.