[magoo666]

Yeah, what you need to do is extract the audio from your video source - either use a video editing prog, video convertor or other demux software to get your audio file. I usually import the video into Sony Vegas, adjust audio levels as required then export to a separate audio file which can be imported into TMPGenc as a substitute for the default video audio.

In TMPGenc, once you have imported your 'source' files, the 'clip properties' dialogue box opens by default. This is where you can specify an alternate audio file (or even an additional one if you are planning to have multi-audio options available). TMPGenc is a good program for simply collating your source files, chaptering & adding a menu, but it is quite basic in terms of what you can actually do with your source files.