you need to know this: no computer is able to properly track audio using a professional DAW (Cubase, PT etc'...) and record video at the same time without fucking at least one of them up.
track with you DAW, shoot with a camera (having audio on the video track will shorten sync time later by about 99%), than when you're done mixing the audio in your DAW sync the stereo mix with the video in a video editing software and mute the videos sound.
done.