If you just filmed a lot of stuff and burn them onto DVD, but unintentionally deleted the original video off the computer, then you can only watch the video on the DVD, you will not be able change anything to DVD; you will not be able to put it back into iMovie nor Quicktime.
If you need to get DVD back into iMovie to make some changes or get some part form the DVD, then it is not a straightforward process, but there is a workaround to do so.
Personally, I would strongly recommend you go with MPEG-4, MPEG-2 and MOV as the video file to rip the DVD to. They usually have much higher video quality and better audio effect.
DVD to iMovie converter for Mac enables you to have full control over video quality; you can set the values of resolution, bit rate, frame rate and keep them them as the highest to get the best effect. The program is also a powerful video editing tool that allows you to trim, crop, add effect and merge files. You can also take snapshots if you need to.
