Re: [FFmpeg-devel] [PATCH] libavfilter/qsvvpp: Use different alignment for YUV420P format

[James Almer <jamrial@gmail.com>]

On 11/29/2022 5:07 AM, wenbin.chen-at-intel.com@ffmpeg.org wrote:
> From: Wenbin Chen <wenbin.chen@intel.com>
> 
> When process yuv420 frames, FFmpeg use same alignment on Y/U/V
> planes. VPL and MSDK use Y plane's pitch / 2 as U/V planes's
> pitch, which make U/V planes 16-bytes aligned. We need to set
> a separate alignment to meet runtime's behaviour.
> 
> Now the commandline works fine:
> ffmpeg -f rawvideo -pix_fmt yuv420p -s:v 3082x1884 \
> -i ./3082x1884.yuv -vf 'vpp_qsv=w=2466:h=1508' -f rawvideo \
> -pix_fmt yuv420p 2466_1508.yuv
> 
> Signed-off-by: Wenbin Chen <wenbin.chen@intel.com>
> ---
>   libavfilter/qsvvpp.c | 12 +++++++++---
>   1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/libavfilter/qsvvpp.c b/libavfilter/qsvvpp.c
> index 8428ee89ab..ad09114cb7 100644
> --- a/libavfilter/qsvvpp.c
> +++ b/libavfilter/qsvvpp.c
> @@ -408,9 +408,15 @@ static QSVFrame *submit_frame(QSVVPPContext *s, AVFilterLink *inlink, AVFrame *p
>       } else {
>           /* make a copy if the input is not padded as libmfx requires */
>           if (picref->height & 31 || picref->linesize[0] & 31) {
> -            qsv_frame->frame = ff_get_video_buffer(inlink,
> -                                                   FFALIGN(inlink->w, 32),
> -                                                   FFALIGN(inlink->h, 32));
> +            /* When process YUV420 frames, FFmpeg uses same alignment on Y/U/V
> +             * planes. VPL and MSDK use Y plane's pitch / 2 as U/V planes's
> +             * pitch, which makes U/V planes 16-bytes aligned. We need to set a
> +             * separate alignment to meet runtime's behaviour.
> +             */
> +            qsv_frame->frame = ff_default_get_video_buffer2(inlink,

I think the proper way to do this is by setting a custom AVFilterPad 
get_buffer.video() callback, which will be called instead of 
ff_default_get_video_buffer() (Which uses an automatically chosen 
alignment at runtime) by ff_get_video_buffer().

See other filters like vf_pad, vf_transpose_vaapi, etc.

> +                                                FFALIGN(inlink->w, 32),
> +                                                FFALIGN(inlink->h, 32),
> +                                                16);
>               if (!qsv_frame->frame)
>                   return NULL;
>   
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