Re: [FFmpeg-devel] [PATCH 1/2] lavu/hwcontext_qsv: add support for AV_PIX_FMT_VUYX

["Xiang, Haihao" <haihao.xiang-at-intel.com@ffmpeg.org>]

On Mon, 2022-08-29 at 08:17 -0300, James Almer wrote:
> On 8/29/2022 4:27 AM, Xiang, Haihao wrote:
> > From: Haihao Xiang <haihao.xiang@intel.com>
> > 
> > AV_PIX_FMT_VUYX is used in FFmpeg for 8bit 4:4:4 content on Intel HW,
> > and MFX_FOURCC_AYUV is used in the SDK
> 
> Sounds like you want the VUYA pixfmt instead.

AV_PIX_FMT_VUYX is used for 4:4:4 content in the VAAPI path, AV_PIX_FMT_VUYX is
expected when creating vaapi urface. QSV is based on 
VAAPI under Linux, so AV_PIX_FMT_VUYX is expected too in the QSV path when
creating vaapi surface.

> 
> > ---
> >   libavutil/hwcontext_qsv.c | 8 ++++++++
> >   1 file changed, 8 insertions(+)
> > 
> > diff --git a/libavutil/hwcontext_qsv.c b/libavutil/hwcontext_qsv.c
> > index 510f422562..a3350eae0f 100644
> > --- a/libavutil/hwcontext_qsv.c
> > +++ b/libavutil/hwcontext_qsv.c
> > @@ -119,6 +119,8 @@ static const struct {
> >                          MFX_FOURCC_YUY2 },
> >       { AV_PIX_FMT_Y210,
> >                          MFX_FOURCC_Y210 },
> > +    { AV_PIX_FMT_VUYX,
> > +                       MFX_FOURCC_AYUV },
> >   #endif
> >   };
> >   
> > @@ -1502,6 +1504,12 @@ static int map_frame_to_surface(const AVFrame *frame,
> > mfxFrameSurface1 *surface)
> >           surface->Data.U16 = (mfxU16 *)frame->data[0] + 1;
> >           surface->Data.V16 = (mfxU16 *)frame->data[0] + 3;
> >           break;
> > +    case AV_PIX_FMT_VUYX:
> > +        surface->Data.V = frame->data[0];
> > +        surface->Data.U = frame->data[0] + 1;
> > +        surface->Data.Y = frame->data[0] + 2;
> > +        surface->Data.A = frame->data[0] + 3;
> 
> This will go wrong with VUYX. You need to use AV_PIX_FMT_VUYA.

frame->data[0] + 3 is valid even if alpha channel is ignored in VUYX. Intel HW
doesn't use the data in alpha channel actually, but the SDK uses Microsoft pixel
format AYUV which is the alpha version, here set a valid address to alpha
channel when mapping a VUYX AVFrame to a AYUV mfx surface. 

Thanks
Haihao

> 
> > +        break;
> >   #endif
> >       default:
> >           return MFX_ERR_UNSUPPORTED;
> 
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