[FFmpeg-cvslog] r16207 - trunk/libavcodec/h264.c

Michael Niedermayer michaelni
Thu Dec 18 04:25:28 CET 2008

On Thu, Dec 18, 2008 at 02:57:17AM +0000, M?ns Rullg?rd wrote:
> michael <subversion at mplayerhq.hu> writes:
> > Author: michael
> > Date: Thu Dec 18 03:53:18 2008
> > New Revision: 16207
> >
> > Log:
> > Use the new idct functions (except chroma as it was slower in benchmarks)
> > cathedral +0.5% speed
> > aladin +0.6% speed [note aladin has been cat-ed 10 times to reduce the influence
> > of init time]
> > Speedup also verified via START/STOP_TIMER (difference was very significant
> > for the changed parts)
> How much does this hurt on architectures that don't yet have the new
> SIMD functions?

there are no really new SIMD functions.
I just moved the loops like
for(i=0; i<16; i++)
    dsp->idct4x4_add(blah blah);

into dsputil so they are

for(i=0; i<16; i++)
    idct4x4_add_simdwhatever(blah blah);

that way gcc can inline the function and avoids up to 15 calls through dsp->

adding support for this to your favorite architecture is a matter of copy
& paste and adjusting the function names.
Of course one could write the loop in asm, and iam sure it would be faster
but i didnt do this ...
Also this is all a little new and i cannot yet gurantee that the API is
stable, though i do not have any plans to change it i might stumble
across further possible improvments ...

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Observe your enemies, for they first find out your faults. -- Antisthenes
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