For home DVDs, insert your DVD into your external player that is plugged into your Mac. When the DVD icon appears on your desktop, click on it to open its contents folder. If the DVD opens for playing, close it. You will see a folder titled VIDEO_TS and another one entitled AUDIO_TS. Ignore the AUDIO_TS. Open the VIDEO_TS folder. You will see several files, some of which have a .VOB extension. Copy, not move, the .VOB extension files to your desktop. (Or, you could copy drag them to your external drive.) Ignore the non-VOV files. The .VOB files contain your movie. They are in Mpeg-2 format. Use the free download, Handbrake, to convert the .VOB files to H.264, Mp4/AAC. Drag the converted files into iMovie for editing.
You can get Handbrake here:
https://handbrake.fr/
A simple way to do it is to open Handbrake and do a File/Open Source. Navigate to your video and choose it as the source from the resulting screen. Then do File/Start Encoding. Wait a couple of minutes for the conversion to complete. Then save and import the converted clip into iMovie. It should work fine. If it doesn't, you can manually insert the above format settings in Handbrake.
-- Rich
