Video encoding and ICC
 

I would need some help from the video pro's around here.

Story is:

Curious beast that I am I figured I try and see what difference if any the Intel compiler (ICC) makes versus GCC.

Installed Gentoo on a VM (Virtualbox) and compiled everything that would compile with ICC and then encoded a video with the command:

time mencoder a.mpg -ovc xvid -xvidencopts bitrate=-50000: pass=2 -nosound -o a.avi

I did run the first and second pass with the VM and the host repectively but there was not much difference in the first pass.

The second pass did this:

Gentoo with ICC in VM

real 1m6.512s
user 0m15.470s
sys 0m47.800s

Debian host

real 2m8.984s
user 2m7.716s
sys 0m1.180s

Needless to say that I was slightly shocked.
Since I don't know how the xvid codec is build for Debian I tried to compile it in the VM with various options including for a i386 cpu but didn't explain the huge difference.

Mencoder can't be it either since that didn't compile with ICC.

Xvid is the same version on both systems.

Could it be related to the fact that the Debian host is a 64 bit system and the VM guest runs 32 bit?

Dazed and confused :scratch:

Maybe so.
The results would need to be compared to a Gentoo system built with gcc instead of ICC.
The difference between those might or might not be that huge.
Gentoo is optimized (rather: can be optimized) for the CPU it is running on. Not just the kernel - but everything.
And that makes a rather large difference when compared to Debian, which is not optimized (built for i386 with no CPU extensions whatsoever being used AFAIK).

That is what I noticed - never confirmed by running tests though aside from comparing the FPS I got from glxgears on Ubuntu (not in a VM - the real one) with what I get on Gentoo on the same machine. It is just the "feel" that it is very noticably faster.
And it is one of the reasons why I use Gentoo.

Actually glxgears was faster for me with Debian when I last checked with a double boot (looong time ago).
Thats probably because the Debian x-guys know a lot more than I do about building X ;)


And well - I did build that system and it is just build with ICC instead of GCC and w/o any special opts (funroll-chick-twice or whatever) - no way that would work on a VM anyway.

Knowing virtualbox (it gave me the fastest cpu in the world with a XP guest and sandra)I even checked the encode times with a stop watch.