Some of you may be familiar with the retelling parody of Harry Potter and the Sorcerer's Stone called Wizard People, Dear Readers by Brad Neely. Essentially it is a re-dubbing of the movie, second for second with the original film. The audio is in the MP3 format. I have encoded the DVD of Harry Potter in Handbrake in the MP4 format and now need to remove the original audio and add the audio track for Wizard People. How do I accomplish this?