[FFmpeg-devel] [PATCH3/3] avfilter YUV aligment 32bytesaligment for Y only and 16 bytes for UV.

[Richard Buteau]

> -----Original Message-----
> From: ffmpeg-devel-bounces at mplayerhq.hu [mailto:ffmpeg-devel-
> bounces at mplayerhq.hu] On Behalf Of M?ns Rullg?rd
> Sent: Wednesday, September 22, 2010 10:19 AM
> To: FFmpeg development discussions and patches
> Subject: Re: [FFmpeg-devel] [PATCH3/3] avfilter YUV aligment
> 32bytesaligment for Y only and 16 bytes for UV.
> 
> "Richard Buteau" <rbuteau at rgbnetworks.com> writes:
> 
> >> On Tue, 21 Sep 2010 20:43:30 +0100
> >> M?ns Rullg?rd <mans at mansr.com> wrote:
> >>
> >> > "Richard Buteau" <rbuteau at rgbnetworks.com> writes:
> >> >
> >> > >> "Richard Buteau" <rbuteau at rgbnetworks.com> writes:
> >> > >>
> >> > >>> Hi all,
> >> > >>> Some encoder don't support linesize[] that aren't multiple. As
> an
> >> > >>> example they expect 720/360/360 for yuv image or 732/368/368.
> >> > >>> the avfilter align all linesize on 16 byte, this make a yuv
> 720/368/368.
> >> > >>> 720 isn't a multiple of 368.
> >> > >>> I added alignment on 32bytes for Y only so it's always
> 732/368/368
> >> > >>
> >> > >> Why?  Nothing requires alignment greater than 16.  If something
> did,
> >> > >> this patch would be the wrong way to fix it.
> >> > >
> >> > > The other option to preserve 2:1 ratio between linesize[0] and
> >> > > linesize[1]/linesize[2]
> >> >
> >> > What makes you believe such a requirement exists?
> >> >
> >> > Also, don't top-post and do quote properly.
> >> >
> >>
> >> I do remember seeing this comment in libavcodec/utils.c in
> >> avcodec_default_get_buffer:
> >>
> >> // NOTE: do not align linesizes individually, this breaks e.g.
> >> assumptions
> >> // that linesize[0] == 2*linesize[1] in the MPEG-encoder for 4:2:2
> >>
> >> Nothing in libavfilter should be making this assumption, but I can't
> be
> >> sure about other code.
> > Does that count as a requirement?
> 
> That could be seen as a bug.  Either way, your patch makes no sense.

Maybe it doesn't make sense but it works. Would you be more helpful and elaborate on how you would fix this?
Have you heard of Intel Avx? it can benefit from 32bytes alignment.
So far I found 3 other codecs in ffmpeg that expect linesize[0] == 2*linesize[1]

> 
> --
> M?ns Rullg?rd
> mans at mansr.com
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