Changing .ISO blu-ray files back into .VOB

If it is a truly standard BluRay disc image, check out BD Rebuilder.

edit: If it's mpeg type HD you can probably take a faster approach than BDRB. But I haven't kept up with the latest changes. If you want near BluRay quality in a standard DVD then BDRB is a good place to start.

A faster method is to use MakeMKV to output an .mkv file from the BluRay. Then do mkv to dvd. You can try AVStoDVD. But what I did, after making one run to initialize the program, is use an AviSynth script and the QuEnc .075 alpha that comes with AVStoDVD, directly. For a 2 hour movie set the bit rate of QuEnc to 8500 constant bit rate. You can use FitCD to create the .avs script for AviSynth to do the frame resizing. This is if you can burn dual layer DVD. I typically got dual layer DVDs about 6 GB in size with fantastic quality. But you need to play around to find the correct filters so that you can size down without getting choppy motion.

Unfortunately there are only a few categories of video where you can just hit the button and everything comes out fine, that are fast. If you want speed and high quality it takes some messing around and learning about codecs, frame rates, and especially Avisynth and its filters.

This site can help a great deal.

edit: for films longer than 2 hours you can use a bit rate calculator. There are free ones on the site at the link I gave.