5.1 surround is considered AC3. 6 channels of PCM audio are combined in an encoder app. Most here will tell you
Discwelder is the way to go. The basic app is around $99-. I have Vegas5 +DVD which does the same thing for PC except you have some automation panning and some good Sony plugins. You can make use the OO1 to simply create the 6 channels. A little searching and you will find some other posts with links on how to set up PTLE I/O for a 5.1 surround session.