[FFmpeg-devel] [PATCH 2/3] simple_idct12: align C and x86
Michael Niedermayer
michael at niedermayer.cc
Wed Oct 14 00:04:49 CEST 2015
On Tue, Oct 13, 2015 at 09:21:40PM +0200, Christophe Gisquet wrote:
> Results for omse on the 3 idct dct-test.
>
> C: 0.16915859 0.11848359 0.12913125
> x86: 0.16883281 0.11849063 0.19041875
>
> Using 14 and 17 as shifts subtantially improve those, but actually
> cause overflows and incorrect decoding of 12bpp content.
> ---
> libavcodec/simple_idct_template.c | 17 ++++-------------
> libavcodec/x86/idctdsp_init.c | 8 +++-----
> libavcodec/x86/simple_idct10.asm | 7 +++----
> 3 files changed, 10 insertions(+), 22 deletions(-)
dct-test -i changes
IDCT SIMPLE-C12: max_err=1 omse=0.11856094 ome=0.00286875 syserr=0.02590000 maxout=288 blockSumErr=64
to
IDCT SIMPLE-C12: max_err=1 omse=0.11825703 ome=0.01024297 syserr=0.05225000 maxout=288 blockSumErr=64
dct-test -i 2
58 2571 1334 1334 1334 1334 58 2571
2571 58 1334 1334 1334 1334 2571 58
58 2571 3805 -1156 3805 -1156 58 2571
2571 58 -1156 3805 -1156 3805 2571 58
58 2571 3805 -1156 3805 -1156 58 2571
2571 58 -1156 3805 -1156 3805 2571 58
58 2571 1334 1334 1334 1334 58 2571
2571 58 1334 1334 1334 1334 2571 58
IDCT SIMPLE-C12: max_err=1 omse=0.12911875 ome=0.06609375 syserr=0.19025000 maxout=256 blockSumErr=64
to
2560 5073 2560 2560 2560 2560 2560 5073
5073 2560 2560 2560 2560 2560 5073 2560
2560 5073 5031 70 5031 70 2560 5073
5073 2560 70 5031 70 5031 5073 2560
2560 5073 5031 70 5031 70 2560 5073
5073 2560 70 5031 70 5031 5073 2560
2560 5073 2560 2560 2560 2560 2560 5073
5073 2560 2560 2560 2560 2560 5073 2560
IDCT SIMPLE-C12: max_err=1 omse=0.19041875 ome=0.15929375 syserr=0.25365000 maxout=256 blockSumErr=64
the ome and syserr values worsen by this
iam not objecting to this if thats what people want, just want to
make sure its not missed
also IIUC this is just to make C and x86 match, so it could just be
skiped with no ill effects except that tnen x86 and C would not be
bitexact matches ?
[...]
--
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
I have often repented speaking, but never of holding my tongue.
-- Xenocrates
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