[FFmpeg-devel] [PATCH 4/5] lavfi: drop the requirement that request_frame returns a frame.

[Paul B Mahol]

On 9/20/15, Nicolas George <george at nsup.org> wrote:
> Le primidi 11 fructidor, an CCXXIII, Paul B Mahol a écrit :
>> One more thing, the query_formats is very limited for filters that pick
>> one
>> pixel format for input and another one for output depending on picked
>> format
>> for input. Returning EAGAIN almost always works but there are special
>> situations when it does not work. There should be query_formats2 or
>> similar
>> which would address such limitations.
>
> The mechanism using EAGAIN is far from perfect, you are right, it is quite
> fragile actually. But to enhance it, saying query_formats2 is not enough:
> it
> would be necessary to tell what would go in it and how it would be used.
>
> In other words, the current algorithm is quite good and elegant for the
> simple cases, but I have no idea how to change in order to make it work for
> complex cases too.

For complex cases one needs to set for which set of input pixel
formats output pixel format will be picked from another set, so its
M->N mapping, without overlaping.

>
> Regards,
>
> --
>   Nicolas George
>