I have a sony handycam DCR-DVD405 and it has taken me many, many hours online to find a way to use iMovie to edit my videos. Since I have the iMac desktop, I can't put the mini DVD into my DVD slot. So, I have to put the mini DVD into my windows laptop and use DVD Rip Pro to rip it and burn it as a video CD.
I put the video CD into the Mac and change the .dat to .mpg on the video file.
Since it's a muxed mpeg 1, I use bbDEMUX to separate the audio file from the video file. It saves it as an .m1a file.
I use Mad Audio Encoder to convert the .m1a to an .aiff file.
I import the original .mpg movie file into iMovie and then I import the .aiff file and put them together.
Finally, something works! Hope this helps someone else.