[FFmpeg-devel] [PATCH] extractplanes filter

[Paul B Mahol]

On 5/2/13, Nicolas George <nicolas.george at normalesup.org> wrote:
> Le duodi 12 floreal, an CCXXI, Paul B Mahol a ecrit :
>> Yes, I'm aware of that, either I could query for different formats if
>> r/g/b are
>> set, or leave it to user by renaming r/g/b/y/u/v to c0/c1.., or just
>> return nothing
>> if input does not have r/g/b.
>>
>> I think I will pick first one.
>
> I am not sure the first one is best: if the user request "r" from a yuv
> input, it will silently insert a convert filter, while this is more likely
> a
> user error.
>
> I suggest something like that:
>
> enum {
>     PLANE_R = 0x01,
>     PLANE_G = 0x02,
>     PLANE_B = 0x04,
>     PLANE_A = 0x08,
>     PLANE_Y = 0x10,
>     PLANE_U = 0x20,
>     PLANE_V = 0x40,
> };
>
> plane_avail = (gray  ? PLANE_Y :
>                rgb   ? PLANE_R | PLANE_G | PLANE_B :
>                        PLANE_Y | PLANE_U | PLANE_V) |
>               (alpha ? PLANE_A : 0);
> if (plane_requested & ~plane_avail) {
>     av_error(ctx, AV_LOG_ERROR, "Requested planes not available\n");
>     return AVERROR(EINVAL);
> }
> plane_actual = (plane_requested & 0xF) | (plane_requested >> 4);
>
>> So return AVERROR_EOF only if EOF happend for all outputs and
>> otherwise just return 0?
>
> Yes, exactly.
>
>> greping shows its required.
>
> Yes, indeed, and seeing it in your patch makes me think we should try to
> make it unnecessary, but that is completely unrelated.

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.

I can't find where its explained how to do that.

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