Assuming they made a surround mix, It would probably be on the DigiBeta in Dolby-E format on channels 3/4, you need to rent a Dolby-E decoder (DP572, i think… might be 571) and connect it to the AES out of channel 3+4. That will give you 6 discreet channels, or 3 AES pairs. You’ll need to then capture all of those tracks. I don’t know if meridian hardware supports that many channels, I believe Adrenaline does. You’ll then need to use a software encoder to process that into an AC3 stream, and put that into your DVD. If you’ve never done this before you’ve got a steap learning curve ahead of you, and may want to subcontract this job out.