Replace audio in video?

I have edited the audio tracks from mp4 video files in Cubase 6 and now I’m trying to merge them back into the source videos.

Cubase has a function called “Replace audio in video” which is supposed to do exactly what I want - replace the original audio track with the new audio track - but it doesn’t work. I get corrupt video files that won’t play.

I have seen videos on Youtube, etc., where this DOES work so I’m wondering what the problem is. Does the audio export have to be in a certain format/samplerate/bitdepth, etc?

I need a fix fast! Any help appreciated.

Hello, I would use a video editing programme for this there are lots available