Will sound mixing in protools recmpress the video?
 

Just wonderin if sound mixing in sound forge, will recompress my video and create more artifacts.

What program would i use to make a 5.1 soundtrack?

I'm not sure what you are getting at here. Normally you don't
have video in an audio application unless you want it there to
guide you in your music creation. Normally you then use a low
resolution proxy instead of the full file.

Why are you worrying about video in an audio application? Make
your audio track and export it as uncompressed WAV in how
many different tracks you want. Then import that into your NLE
(editor) and output to your final format (I presume DVD due to
you mentioning 5.1). For DVD you create an AC3 file and MPEG2
video file (you might even be able to create the AC3 file in
Sound Forge and bypass audio creation in the NLE?) and load
that up in a DVD authoring package to create your DVD structure.

Then either your authoring program burns the DVD as well or
you can have some other burning program do that.

Your main issue is the MPEG2 video compression with whatever
codec you use (Premiere 6.5 & Pro come with their own, as does
Vegas, but you can also go down the standalone encoder route
through program likes Canopus ProCoder or TMPGEnc).

Thanks fr the info Rob, still leabes me wondering where can i do a 5.1 mix? Also do most people just edit the sound in the NLE? or do they export the tracks to something like SoundForge, id prefer to do it all in premiere 6.5, but how do i go from say 3 audio tracks to 5.1?

SoundForge is an audio editor that handles noise reduction, dialogue editing, but not multitracking (have multiple tracks of audio like your NLE does). You'll need a program like Adobe Audition for that (Audition should be bundled with Premiere Pro). I'm not sure if Audition can handle 5.1.

2- You probably don't need 5.1. What are you trying to do (overall with your sound)?