[Ffmpeg-devel] patch: altivec optimizations for h264 decoder

Romain Dolbeau romain
Mon Feb 6 14:07:57 CET 2006

Michael Niedermayer wrote:

> mixing declarations and statements, romain is this an issue for ppc-asm or do
> all compilers which support ppc-asm support this too?

They probably do. It would be intesrting to know what OS and compiler
the author of the patches used (I don't have linux/ppc anymore).

> romain please review and test, you are the ppc maintainer

I am ? damn, more responsabilities :-/
I can't test, as I don't have a sample, and if I had,
I don't have a machine fast enough for 1080p anyway
(the G4 isn't the fastest CPU around...)

Patch 1 : nothing to add, except that gcc register allocator is probably
going to hate ff_h264_idct_add_altivec_mat

Patch 2 : in PREFIX_h264_qpel4_hv_lowpass_altivec, why use
VEC_LOAD_UNALIGNED_CHECK ? tmpbis is computed from tmp
(comments -> assumed aligned) and tmpStride (comments ->
multiple of 16), so it has to be aligned.

Patch 4 : is put_pixels8_altivec really faster than the C
version ? there's not computation whatsoever, and with the
need to load the destination block to insert the new
data, it may be slower to use AltiVec than regular C code.

I'm a little bit short on time to be able to make a more
thorough investigation, sorry

Romain Dolbeau
<romain at dolbeau.org>

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