M2v is just a standard MPEG with the audio stripped out. When you export the file from your editing program to begin with, it may be an option (you'd chose to export as an Mpeg, or a mpeg dvd or something, and then choose "no multiplexing." Alternatively, make the file an Mpeg from your editing software, open the mpeg in MPEG streamclip, and choose "demux" which will give you an m2v file and an aiff file.