step 2: phase invertion
it's really pretty simple. so forget the dvd for a second and just import any audio file into some audio editing software, like cubase or whatever. duplicate the audio track so that you have 2 of the exact samae audio file playing at the same time. press play just to check, everything should be really loud since 2 of the same audio file is playing at the same time right? ok, now find in your software something that says "phase invertion" or "invert phase" or some combination. apply that setting to ONE of those audio files... and press play. you should be hearing absolute SILENCE even though meters are moving and audio is playing. now try bringing one of the volume faders down for one of the audio files. you should hear the audio slowly coming up in volume. THIS is the phenomenon of PHASE CANCELATION!
lets say you have an instrumental track of a band and a full mixed track with instruments and vocals. do the same thing to the above, flip the phase of one while they are playing at the same time and all you hear now is the VOCALS!
so back to the dvd, you are listening to just the center channel right? but it has music and sound effects in the background. what can you do!?!? this is how you will get any unwanted audio out off that dvd of yours. you extract the left and right channels of the dvd, extract the center channel, import them and make sure they are playing together PERFECTLY TOGETHER down to the .00001th of a millisecond. flip the phase of the center channel and hit play. you will hear some weird stuff going on but you're not done yet. save that mix as an audio file as well then import it into your session. re-filp the vocals back in phase and then flip the newly imported audio out of phase and play everything together. finally, you should hear just the vocals by themselves with maybe a little bit of weird stuff in the background. and there you go, you should have a much more usable audio file!
