Ripping the already compressed dvd copy of the video to an MP4 then transcoding yet again to DV or other format on top of that is just degrading the image more and more. If you can’t get access to the original footage then instead of using MacTheRipper / Handbrake or whatever to rip the VOB to an MP4 first, just download and use the free MPEG Streamclip application to transcode the file directly from your friend’s DVD to a DV-NTSC file that you can edit with easily.
If transcoding is really what you want to do though, then you can use Compressor or Quicktime Player (or MPEG Streamclip) to transcode the file.