if i'm not mistaken, dual audio in VCD use the right or left channel audio to do the trick. not like in a dvd which we can choose the audio stream in a menu.

i think that you should have no problem to change to cantonese after burning into a dvd (without any modification b4 burning). just change the audio to either right or left channel.

never experiment it b4, u can try it.

but if u wan to seperate the audio b4 burning. that's a tricky job.