Re: [FFmpeg-devel] [FFmpeg-cvslog] swscale/output: add VUYA output support

["Martin Storsjö" <martin@martin.st>]

On Sun, 7 Aug 2022, James Almer wrote:

> ffmpeg | branch: master | James Almer <jamrial@gmail.com> | Fri Aug  5 13:44:16 2022 -0300| [19748132613d1d13f5b6786051910e7375bb3df6] | committer: James Almer
>
> swscale/output: add VUYA output support
>
> Signed-off-by: James Almer <jamrial@gmail.com>
>
>> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=19748132613d1d13f5b6786051910e7375bb3df6
> ---
>
> libswscale/output.c                      | 57 ++++++++++++++++++++++++++++++++
> libswscale/utils.c                       |  2 +-
> tests/ref/fate/filter-pixdesc-vuya       |  1 +
> tests/ref/fate/filter-pixfmts-copy       |  1 +
> tests/ref/fate/filter-pixfmts-crop       |  1 +
> tests/ref/fate/filter-pixfmts-field      |  1 +
> tests/ref/fate/filter-pixfmts-fieldorder |  1 +
> tests/ref/fate/filter-pixfmts-hflip      |  1 +
> tests/ref/fate/filter-pixfmts-il         |  1 +
> tests/ref/fate/filter-pixfmts-null       |  1 +
> tests/ref/fate/filter-pixfmts-pad        |  1 +
> tests/ref/fate/filter-pixfmts-scale      |  1 +
> tests/ref/fate/filter-pixfmts-transpose  |  1 +
> tests/ref/fate/filter-pixfmts-vflip      |  1 +
> 14 files changed, 70 insertions(+), 1 deletion(-)

The new tests for vuya fail in all ARM configurations.

The issue disappears if running with CPUFLAGS=0 - but the issue isn't tied 
to any specific ARM specific assembly routine, but seems to be triggered 
by "filterAlign = 2" for the vertical luma filter.

To reproduce the issue on x86, apply this patch:

diff --git a/libswscale/utils.c b/libswscale/utils.c
index 34503e57f4..e70281d74f 100644
--- a/libswscale/utils.c
+++ b/libswscale/utils.c
@@ -1855,11 +1855,11 @@ av_cold int sws_init_context(SwsContext *c, 
SwsFilter *srcFilter,
          const int filterAlign = X86_MMX(cpu_flags)     ? 2 :
                                  PPC_ALTIVEC(cpu_flags) ? 8 :
                                  have_neon(cpu_flags)   ? 2 : 1;

          if ((ret = initFilter(&c->vLumFilter, &c->vLumFilterPos, &c->vLumFilterSize,
-                       c->lumYInc, srcH, dstH, filterAlign, (1 << 12),
+                       c->lumYInc, srcH, dstH, 2, (1 << 12),
                         (flags & SWS_BICUBLIN) ? (flags | SWS_BICUBIC) : flags,
                         cpu_flags, srcFilter->lumV, dstFilter->lumV,
                         c->param,
                         get_local_pos(c, 0, 0, 1),
                         get_local_pos(c, 0, 0, 1))) < 0)

I.e. hardcode passing filterAlign=2 to initFilter for vLumFilter. When 
running e.g. fate-filter-pixfmts-vflip with this modification on x86 
normally, it works, but if one runs the same with CPUFLAGS=0, it fails.

Thus, something in the vertical scaler fails if the the filter is 
overaligned; fails only for the vuya format test and nothing else. But the 
x86 assembly seems to cope with it.

Can you please have a look?

// Martin

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