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

[Mark Thompson]

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 ...

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.

- Mark