[FFmpeg-devel] [PATCH] lavu/get_video_buffer: also align data pointers

[Pavel Koshevoy]

On Sat, Nov 9, 2024 at 10:27 AM James Almer <jamrial at gmail.com> wrote:

> On 11/9/2024 1:57 PM, Pavel Koshevoy wrote:
> > This avoids unpleasant surprises to av_frame_get_buffer callers
> > that explicitly specified 64-byte alignment and didn't get
> > AVFrame.data pointers that are 64-byte aligned.
>
> Again, the doxy is clear that only the buffer sizes are aligned, not the
> pointers. I'd rather not make this change here. Please see
> https://ffmpeg.org//pipermail/ffmpeg-devel/2024-November/335811.html
>
>
So if we update the doxy then the change will be accepted?
I don't understand the reluctance to improve the behavior of this API.




> >
> > In particular, this fixes an issue in vf_zscale.
> > https://github.com/sekrit-twc/zimg/issues/212
> > ---
> >   libavutil/frame.c | 4 +++-
> >   1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/libavutil/frame.c b/libavutil/frame.c
> > index f0a0dba018..7faf7aeae8 100644
> > --- a/libavutil/frame.c
> > +++ b/libavutil/frame.c
> > @@ -216,6 +216,7 @@ static int get_video_buffer(AVFrame *frame, int
> align)
> >           total_size += sizes[i];
> >       }
> >
> > +    total_size += align - 1;
> >       frame->buf[0] = av_buffer_alloc(total_size);
> >       if (!frame->buf[0]) {
> >           ret = AVERROR(ENOMEM);
> > @@ -223,7 +224,8 @@ static int get_video_buffer(AVFrame *frame, int
> align)
> >       }
> >
> >       if ((ret = av_image_fill_pointers(frame->data, frame->format,
> padded_height,
> > -                                      frame->buf[0]->data,
> frame->linesize)) < 0)
> > +                                      (uint8_t
> *)FFALIGN((uintptr_t)frame->buf[0]->data, align),
> > +                                      frame->linesize)) < 0)
> >           goto fail;
> >
> >       for (int i = 1; i < 4; i++) {
>
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