[FFmpeg-devel] [PATCH] extractplanes filter

[Paul B Mahol]

On 5/3/13, Nicolas George <nicolas.george at normalesup.org> wrote:
> Le tridi 13 floreal, an CCXXI, Paul B Mahol a ecrit :
>> I wonder how format renegotiation works. I would like to pick 16bit gray
>> with right endianess depending on input format - if its 16 bit at all
>> otherwise just pick 8bit one.
>
> That would be useful in this situation indeed.
>
> The basic principle is this: query_formats() sets the formats it can, and
> if
> it could not set everything it returns EAGAIN, and will be called again
> later, hopefully when more information is available.
>
> In this situation, I believe the correct flow is this:
>
>     if input formats are not set
>         set input formats to all 8 and 16 bits formats
>     if input formats still contains several bit depths
>         return AVERROR(EAGAIN)
>     else
>         set output formats to the corresponding gray format

This still does not explain what input formats means. Inputs formats
of inlink or output formats
of inlink?

I get nice forever loop if set out formats for inlink and than expect
it to change.

So its not that simple like it appeared at first.

>
>> I can't find where its explained how to do that.
>
> There is a small paragraph in doc/filter_design.txt, it could be expanded,
> possibly with an example.
>
> Regards,
>
> --
>   Nicolas George
>