Using I-Author Multiplexer

I am trying to make a few anime movies into SVCD's for my self and i have followed the doom 9 guide to the letter, except when it comes to the i-author multiplexer. I am unable to come up with the right file extentions in order to use the multiplexer. The video source requires and .MPV file; i only have an M2V file. I am also wanting to have two seperate audio tracks (one for the Japanese and the English), however, i don't have an MPA file for the second audio stream. How do i come up with these specific file extentions?? thanks for any help

did you try to rename them? jj

Alternatively, change the filemask to *.* in the file/open dialogs - you will be able to load any file you want.