Hey,
Downloaded mp4 files off iPhone and burn the videos into DVD disc, you need one mp4 to dvd burner program, i personally used iMacsoft DVD Creator, can easily burn MP4 files into movie DVD disc very fast.
http://www.imacsoft.com/dvd-creator-mac.html
And you can also use it to burn AVI, 3GP, MKV, FLV, WMV, MPEG, etc, to dvd disc, for the detailed info you can refer to the below link to learn:
http://imacsoft.com/how-to-convert-mp4-to-dvd-mac.html