[FFmpeg-devel] [PATCH] ARM: NEON optimised simple_idct

[Michael Niedermayer]

On Mon, Aug 25, 2008 at 04:06:33AM +0100, Mans Rullgard wrote:
> ---
>  libavcodec/Makefile                  |    2 +
>  libavcodec/armv4l/dsputil_arm.c      |   15 ++
>  libavcodec/armv4l/simple_idct_neon.S |  383 ++++++++++++++++++++++++++++++++++
>  libavcodec/avcodec.h                 |    1 +
>  libavcodec/utils.c                   |    1 +
>  5 files changed, 402 insertions(+), 0 deletions(-)
>  create mode 100644 libavcodec/armv4l/simple_idct_neon.S
> 

is this idct binary identical in output to the C/MMX simple idct?


[...]
> +#ifdef HAVE_NEON
> +        } else if (idct_algo==FF_IDCT_SIMPLENEON){
> +            c->idct_put= ff_simple_idct_put_neon;
> +            c->idct_add= ff_simple_idct_add_neon;
> +            c->idct    = ff_simple_idct_neon;
> +            c->idct_permutation_type = FF_NO_IDCT_PERM;
> +#endif

I do not know neon at all but, ive never seen a SIMD instruction set for
which the identity permutation would have been optimal.

Also i suspect that the MMX simple idct is a better basis from which to
write other SIMD variants of the simple idct than the C one.

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

If you really think that XML is the answer, then you definitly missunderstood
the question -- Attila Kinali
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