DVDFlick is a free software that can burn AVI, MPG, MOV, WMV, ASF, FLV, Matroska and MP4 videos to DVD.

You can also use many audio/video converters like Replay Converter to burn MP4 files to DVD.

As for an audio file, it really depends on how you wanna have it on a DVD. Do you want it to be in a DVD menu, do you want to be able to listen to it while watching black screen?