How to change libjpeg?

[netnet]

Somebody wrote to change default jpeg libraries to get mmx performance.

I have centos with libjpeg.x86_64
Package libjpeg-6b-37.x86_64 already installed and latest version
Package libjpeg-6b-37.i386 already installed and latest version

Can I change it to get better performance?

[kingofkya]

Theres a newer version called jpeg turbo or some thing like that check contribs