3. How To Rip a DVD

VOB files are MPEG2 files, so you could play them directly in a software DVD player. But special features like multiple angles and branching can cause problems. Also, details like the aspect ratio are in the IFO files, so you need to copy or extract multiple files. The largest IFO file will be the title set for the main film; usually that's VTS_01_0.IFO.

The menu is in the VTS_01_0.VOB file and the movie footage and soundtrack in VTS_01_1.VOB, VTS_01_2.VOB and so on. Most DVD copying tools let you preview the image - so you can check that you have the right set of files - and some even automatically select the main content. Note that if you have a two-sided DVD or a series of shorter episodes, you'll have more title sets to copy.

How and what you copy depends on what you want to do with the video. For a backup copy, you may want to replicate everything in the disc at the highest possible quality. But in many cases you will just want the main content and not the extras. Pre-recorded DVDs have more capacity than most recordable DVD discs, so you'll need to split the content over two discs, reduce the quality, or leave things out.

You can reduce an 8 GB DVD to around 4 GB by removing extras, menus, surround sound and alternative soundtracks, and trimming off the credits. Subtitles don't take up enough space to worry about, but some programs can remove those too. You can add some of the extras back if you want to include them, once you know how much space it's all going to take.

Many programs will strip out the black bars around widescreen movies and put them back in the final encoding, so they're not taking up file space. Auto Gordian Knot lets you reduce the quality of the credits if you don't want to cut them out entirely, which will save 40 to 50 MB.

Turn off subtitles to save space, unless you know you'll need them.

If you want the backup to fit on a CD rather than a DVD, you need to convert it to a Video CD (VCD) or Super Video CD (SVCD). If you're going to play the content on a PC or with other content on a Media Center PC, or if you are trying to save battery life on a notebook PC, you could leave the VOB files as they are. You can save disk space, however, by converting to a format like WMV or AVI and still keep high quality video.

Alternately, you can speed the process up by transcoding the MPEG content with a program like DVD Shrink, reducing the quality without actually re-encoding the whole video file. And if you're going to play it on a portable player, you'll want to resample the video to the right screen resolution. This means you will want a file format that shrinks the file size, but that may be dictated by what your player supports.

You'll need a utility like Magic DVD Ripper to convert to the correct format for iPod video or playing on a Sony PSP; this will also set the correct resolution. For most devices, the MPEG4 formats like DivX and XviD are a good compromise between compact files and good quality; DivX is better known, but XviD is open source and lets you choose what size of file you want to end up with rather than picking a bitrate. For mobile phones that play video, the format is often 3GP.

You'll get the best sound quality by sticking with the Dolby AC3 sound encoding. But if you have a very long movie or you're short on space, MP3 audio will take up less space. Classic movies may have a dual mono soundtrack; convert to single channel and you can save even more room. Be careful with programs that allow you to choose the final output size so you can fit it onto a Video CD (or similar). If you pick AC3 and a small file size, you'll get poor video quality because the audio will take up too much of the space.