[FFmpeg-devel] [PATCH 1/6] lavu/pixfmt: add new pixel format ayuv/y210/y410

[Hendrik Leppkes]

On Wed, Sep 11, 2019 at 5:20 AM Fu, Linjie <linjie.fu at intel.com> wrote:
>
> > -----Original Message-----
> > From: ffmpeg-devel [mailto:ffmpeg-devel-bounces at ffmpeg.org] On Behalf
> > Of Carl Eugen Hoyos
> > Sent: Wednesday, September 11, 2019 03:25
> > To: FFmpeg development discussions and patches <ffmpeg-
> > devel at ffmpeg.org>
> > Subject: Re: [FFmpeg-devel] [PATCH 1/6] lavu/pixfmt: add new pixel format
> > ayuv/y210/y410
> >
> > Am Di., 10. Sept. 2019 um 18:08 Uhr schrieb Linjie Fu <linjie.fu at intel.com>:
> > >
> > > Add some packed pixel formats for hardware decode support
> > > in VAAPI and QSV:
> > >
> > > 4:2:2 10 bit: Y210
> > > 4:4:4  8 bit: AYUV
> > > 4:4:4 10 bit: Y410
> >
> > Please add a short explanation (either in the commit message or
> > only in this thread) for which kind of samples these pixel formats
> > are needed.
> >
> > Or to say it differently: Why is the hardware outputting planar
> > formats for some samples and packed for others?
>
> I kind of remember that it was discussed in previous patch thread:
> Previously, media driver provided planar format(like 420 8 bit),
> but for HEVC Range Extension (422/444 8/10 bit), the decoded image
> is produced in packed format. And the reason is " because Windows
> expects it" as you have pointed.
>
> It could be updated in the commit message if this is good enough.
>
> > I see you added LE and BE versions: Why are both needed?
> > And if they are needed, why is there only AYUV and not AYUV
> > and VUYA?
>
> I noticed LE and BE versions are added for some of the added pixel
> format, out of the compatibility for big-endian and little-endian(IMHO).
> And that's the reason I add it for Y210 and Y410.
>
> I'm not sure I understood it correctly, LE/BE version is necessary for
> newly added pixel format right?
>

It depends on  the definition of the pixel format. AYUV is defined as
4 consecutive BYTEs, which means its identical on LE and BE.
Y210 is defined as being stored as an array of 4 WORDs (Y0, U, Y1, V).
For a WORD, the difference of LE/BE matters.
Y410 is defined as being stored as a single DWORD, again LE/BE matters here.

Obviously the differences in LE/BE need to be implemented properly as
well, for Y210 for each WORD, and for Y410 for the entire DWORD.

- Hendrik