From ModMyiFone - Wiki
Note: On aug 3 the previous version of this page linking to the freeware Videora Video Converter was changed by the user Mrxxg to point instead at a shareware product that requires payment to avoid watermarks, complete with affiliate links (note the 56510 part of the filename). I am reverting this to the older page linking to the freeware application, if you want the shareware application check this article's history. I'm doing this one time only, if anyone wants to play edit war I do not care.
by fireraining
Windows user
What you need is DVD Decrypter and Videora iPhone Converter, they are both free.
DVD Decrypter.
Videora iPhone Converter.
Part1. Rip DVD to computer:
Step1. Install DVD Decrypter and run it, put your DVD disc into your DVD-Rom, Go to the Mode menu and select IFO I mode. This will give you access to two new tabs; Input & Stream Processing.
Step2. Go to the Tools menu, select Settings, go to the IFO tab, then under Options, change File Splitting to none and press OK.
Step3. Go to the main screen and click the Stream Processing tab. Enable it and only select the first video listed. Note that home encoded movies do not support subtitles of any kind and that your file can only have one type of audio.
Then click “Decrypt” button to start ripping your DVD to hard drive.
Part2. Convert the ripped DVD or video to MP4 for iPhone
Step1. Install Videora iPhone Converter and run it.
Step2. After you open Videora, click “Convert” tab, then select “Current Conversion” tab, click “One-Click Converter”, and load your video files. Then the conversion will start automatically. When you finish the conversion, Videora will add the converted video to iTunes library.
If DVD Decrypter + Videora iPhone Converter didn’t help, you can try other iPhone converter tool such as Aimersoft iPhone Converter Suite, this software can help you rip DVD and convert video to iPhone, and here is a full guide about it.
Transfer video to iPhone
Run iTunes (you need iTunes 7.3.0 or later), drag the converted video (*.mp4) to your iTunes library, connect your iPhone to computer; iTunes will detect your iPhone when you connect iPhone correctly. Then click “Sync iPhone”, done.
iTunes download link.
If you have any question about this guide, feel free to post here.