[FFmpeg-devel] [PATCH 1/2] lavu/pixfmt: add AYUV pixel format

[Fu, Linjie]

> -----Original Message-----
> From: ffmpeg-devel [mailto:ffmpeg-devel-bounces at ffmpeg.org] On Behalf
> Of Mark Thompson
> Sent: Saturday, August 31, 2019 23:10
> To: ffmpeg-devel at ffmpeg.org
> Subject: Re: [FFmpeg-devel] [PATCH 1/2] lavu/pixfmt: add AYUV pixel format
> 
> On 31/08/2019 05:22, Fu, Linjie wrote:
> >> -----Original Message-----
> >> From: ffmpeg-devel [mailto:ffmpeg-devel-bounces at ffmpeg.org] On
> Behalf
> >> Of Carl Eugen Hoyos
> >> Sent: Friday, August 30, 2019 00:12
> >> To: FFmpeg development discussions and patches <ffmpeg-
> >> devel at ffmpeg.org>
> >> Subject: Re: [FFmpeg-devel] [PATCH 1/2] lavu/pixfmt: add AYUV pixel
> format
> >>
> >> Am Do., 29. Aug. 2019 um 16:16 Uhr schrieb Fu, Linjie
> <linjie.fu at intel.com>:
> >>
> >>> Thus AYUV will make more sense.
> >>
> >> If your hardware decoding does not produce valid alpha data (0xFF
> >> for opaque, 0x00 for completely transparent), you cannot use an
> >> FFmpeg pix_fmt that defines alpha for decoding.
> >> If you define a pix_fmt that does not contain alpha information (as
> >> needed for your hardware decoder), please do not use "A" in its
> >> name.
> >
> > The hardware decode output is in packed 4:4:4:4 8 bit(32 bits in total). Apart>
> from Y/U/V channel, there is an additional need for a channel to store the
> > zero byte in surfaces(nb_components = 4). And it is designed in
> hardware/driver
> > for VA_FourCC_AYUV and AYUV format.
> >
> > It's not quite proper to use something like "0YUV" directly which indicates
> that
> > there is no Alpha channel data like"RGB0" or "0RGB"(nb_components = 3).
> >
> > "0YUV": YUV0/YUV0/...
> > "RGB0":RGB/RGB/...
> 
> I think you've misread what RGB0 is.  The component step is 4, not 3 (see
> libavutil/pixdesc.c) - the format with a step of 3 is RGB24.
> 
> RGBA:  R G B A R G B A ...
> RGB0:  R G B 0 R G B 0 ...
> RGB24: R G B R G B R G ...

Thanks for pointing out this.
Just took the nb_components into account and misread the step info at first.
 
> Following the same pattern we would have:
> 
> AYUV:  A Y U V A Y U V ...
> 0YUV:  0 Y U V 0 Y U V ...
> 
> To me it looks like 0YUV is exactly what you want here.

Will update the patch if 0YUV is more acceptable.
And thanks Carl.

- linjie