I learned how to turn a DVD into a DivX today. The secret is the program Gordian Knot along with the guide from Doom9. It’s very confusing hackerware, but the basic idea is

1. Rip with SmartRipper. Produces VOB files - video objects ripped from the DVD.
2. Decode and parse with DVD2AVI. Produces AC3 audio files, as well as a D2V file that seems to be a guide to the video in the VOB.
3. Configure codec (DivX 3, in this case). Have to choose bitrate, audio track, etc.
4. Encode. Produces an AVI that the movie player can show.

Gordian knot tries to glue all these steps together for you. It’s hugely confusing, but the Doom9 guide helps. It helps a lot if you set the Bitrate tab to “Calculate Avi File Size” - then you set quality directly rather than trying to guess a quality to fit a certain size file.

End result - 3:1 compression ratio for something that still looks very good (704x368@1600kbps, 160kbps MP3 audio). Three things would make this process better:

• Encode direct from camera to MPEG-4, bypassing the MPEG-2 step in the DVD.
• Variable bitrate encoding during construction of MPEG-4 stream. Maybe DivX does this, but I don’t think so. (Whoops, Nandub, which I’m using, does do this.)
• Turn DivX encoding into a legitimate business so someone can write a good front end. Rip, mix, burn.