I just replaced my car stereo thinking I could use the USB in, I couldn't get it to work by default.
I'm left with using the aux in, which is nothing more than a stop gap solution.
Hoping that I can get it to work with usb too
I forgot to try system >accessories >usb audio
I'll try when I get out of work.
2nd edit :
Samsung Galaxy S III
ROM: Omega v. 34
KER: Boeffla kernel 2.6