[Ffmpeg-devel] [PATCH] put_mpeg4_qpel16_h_lowpass altivec implementation

[Brian Foley]

Hi there,

please find attached a first cut at some Altivec acceleration for the
mpeg4_qpel functions. To get things started, I've translated
put_mpeg4_qpel16_h_lowpass from the C version, as it was the most CPU
intensive function that showed up when playing some 720p Xvid.

A clip that benchmarked at 11.6s before now takes 9.0s on my 1.8GHz
G5 iMac, and that 720p Xvid no longer drops frames in the places it
used to before.

It should be a safe enough patch to apply, as I've tested it fairly
carefully with a large set of random inputs, focussing on things that
could cause overflow/rounding errors. As far as I can tell, it gives
exactly the same outputs as the C version in every case.

Other obvious candidates to Altivec-ify are put_mpeg4_qpel16_v_lowpass,
all the avg_mpeg4 equivalents, and the mpeg4_qpel8 variants. I'll try
to get around to doing some of those soon if someone doesn't beat me to
it :)

Cheers,
Brian Foley.
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