[x264-devel] Regression in encoding speed from 20090629 version to later versions

[devsk]

Hi,


I have a Gentoo AMD64 system here and I
encountered a regression in encoding speed with mencoder recently with
an update which updated x264 package from 20090629 to a later version.

With the same command line options,
I get about 235FPS for a 1 pass encode with 20090629 version but I get
about 175FPS with versions later than 20090629, on the same MPEG
material. I repeatedly tested it by going back and forth between
version with 'emerge -vK1 x264', and results are same: On the same MPEG
source, with same x264opts, FPS has reduced by about 25-30%.

The
options I am using are: -x264encopts threads=12:psnr:bitrate=1200.
Basically, nothing fancy. threads=12 give the best output with this i7
920 X58 system. I have tried other lower values of the threads as well and the mencoder FPS just falls.

I have tried a few other mpeg streams as well and repeated the same experiment and the behavior is same.

I am using vanilla-sources-2.6.32-rc8 with HZ=300 (HZ=1000 seems to speed up multi-threads encoding), NOHZ, Voluntary Kernel Preemption and Highres Timer.

I am wondering if anybody else has noticed this regression in speed. Its quite substantial.

Thanks,
-devsk