Jag orkar inte översätta men det här kanske kan hjälpa dig:
It's not easy. First you have to use a program called DVD Backup to strip the various copy protections then you will have to convert the VOB files to video and audio. I found a site that went through the steps dont have the link but I'll paste the info
Extracting a clip from a DVD
How to spice up a Keynote presentation, or put together a compilation of your favorite clips from DVD. With acknowledgements to Sean Willard and Vicki Robinson who did all the heavy lifting here.
Use DVDBackup to rip the DVD , producing a bunch of .VOB files. This requires upwards of 4GB of hard disk space. Alternatively, use 0Sex with its appalling user interface to extract just the section you need.
Using OSex has an advantage: it does the audio demuxing at the same time, saving .m2v (MPEG2) and .ac3 (Dolby Digital) files separately. Using either tool, you may also choose just the title and chapter (.vob) you want.
Use Extractor to demux (split into separate audio and video) the .vob file you're interested in. This results in .m2v and .ac3 files (if you didn't already do this with 0Sex). To figure out which .vob file you want, view them with VLC.
Extractor comes from http://denisx.dyndns.org/extractor/ . It is an easy tool to demux vob files.
Pay Apple $20 for the MPEG2 plugin for QuickTime. It's the most user-friendly way to convert DVD video on the Mac, though you still need to demultiplex ("demux") VOB data into separate MPEG2 (a.k.a. .m2v) and (usually) AC3 streams. You'll use it in the next step.
Use MacMPEG2Decoder to convert the .m2v to the format of your choice. This uses QuickTime to encode the output, so you have your choice of any QuickTime codec you have installed or might add (like DiVX or MPEG2 -- but be warned, QuickTime won't let you edit an MPEG2 movie, just view it or export to a different format, and that only if you've paid the $20 for the MPEG2 codec; so MPEG2 is probably best reserved for mastering DVDs and such).
Alternatively, if you have paid for the MPEG2 codec, open the .m2v with QuickTime Pro Player and do File->Export to the format and codec of your choice. Many people pay for this QT add on, since they use QT Pro constantly. This exports from mpeg2 to QT, and the encoding takes a fair time.
Use bd4go to convert audio .ac3 files to .aiff. It would be nice to use iTunes to do this, but apparently not.
bd4go comes from http://denisx.dyndns.org/bd4go/ . It is an easy tool to convert .ac3 files into .aiff or .wav format.
Open the .aiff file in QuickTime Pro Player . You need to buy a QT Pro key from Apple. Choose "Select All" from the Edit menu, and Copy.
You may find there are several .ac3 files and only one mpeg2. These are various languages, director commentary etc. Play them from iTunes or the Finder to locate the one you want.
Open the QuickTime movie from step 3 in QT Pro. Put the slider at the beginning of the movie. From the Edit menu, select "Add" or "Add Scaled" (the latter will squeeze the tracks to match if they are of different lengths).
To align audio and video timing, read the OS X DVD Tutorial. It advises to add the video to the audio, not the other way round. Scaling the video gives a much better result than scaling the audio for some reason.
Save as a self-contained movie.
It's easier than on Windows -- the hardest part was figuring out the right tools to use.
