[PD] CPU usage with multiple cameras and different operating systems. (Gem)
crinimal at gmx.net
Wed Jul 22 19:51:48 CEST 2009
I'm developing an installation which currently uses six webcams
(Logitech Vision Pro, but tried also lots of other cameras). I'm using
Gem patches on Linux and OS X and realized that OS-X's CPU consumption
is much less than on linux. I made tests with a single webcam on Linux
and single (and multiple webcams) on OS X. Both computers are not
directly comparable, because of different hardware, but maybe this is
The Linux computer: AMD Athlon64, 2.2 GHz, GeForce 7600 GS, nvidia
proprietary driver, Kernel 2.6.30-ARCH (and also other kernels from
debian and ubuntu), webcam @ 640x480, 30 FPS. Measurements of CPU
consumption are done using htop, on the above described computer.
The OS-X 10.5 Computer: Macbook pro 2x2.2 GHz, Geforce M 8xxx (don't
know exactly, it's not my computer, but I can look more accurate if
someone wants to know.) Measurements are made by using top (and OS-X
activity monitor, which seem to be the same)
when using one webcam in cheese or luvcview it's using approximately 40%
when using the same webcam in Gem's pix_video help Patch it's
approximately 80% CPU usage
didn't test simple application like cheese, but:
one webcam in pix_video help patch uses 15% cpu.
Gem, single webcam: approx. 15% usage
Gem, three webcams: approx 20%
For comparison in other programs on Linux and with other video content
Gem, pix_movie (352x288, 25 fps, mpg) 10% cpu usage
Gem pix_movie (720x480, 24 fps, quicktime) 59% CPU
mplayer - vo gl: (720x480, 24 fps, quicktime) 62% cpu
mplayer -vo null: (720x480, 24 fps, quicktime) 40% cpu (40% for
decoding? or is there already some system overhead?)
so it seems "normal" to have such huge cpu consumptions for video replay
and cameras on linux?
I didn't measure it, but I also had extremely high cpu usage when using
firewire dv cameras some time ago.
where does this big difference come from? does OS-X use video decoding
on graphics card or something similar?
any ideas for making video faster on Linux?
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