DVD 101

DVD is the next generation of optical disc storage technology. It's essentially a bigger, faster CD that can hold video as well as audio and computer data. DVD is often called a convergence medium since it encompasses both home entertainment and information storage, eventually replacing audio CD, videotape, laserdisc, CD-ROM, and even videogame cartridges.

DVD has widespread support from all major electronics companies, all major computer hardware companies, and all major movie and music studios. With this unprecedented level of support, DVD has become the most successful consumer electronics product of all time within only three years of its introduction.

It's important to understand the difference between DVD-Video and DVD-ROM. DVD-Video (often simply called DVD) holds video programs and is played in a DVD player hooked up to a TV. DVD-ROM holds computer data and is read by a DVD-ROM drive hooked up to a computer. The difference is similar to that between audio CD and CD-ROM.

Most computers with DVD-ROM drives can also play DVD-Video discs. DVD-ROM also includes recordable variations (DVD-R, DVD-RAM, DVD-RW, and DVD+RW). A super-high-fidelity DVD-Audio format is also available.

DVD-ROM drives (DVD Players) are steadily replacing CD-ROM drives in computers. Most forecasters expect manufacturers to stop making CD-ROM drives in 2001 or 2002. Since all DVD drives can read CDs, anyone buying a new computer should strongly consider getting one with a DVD drive.

DVD comes in two physical sizes, the same form factors as CD. A DVD disc can be single-sided or double-sided. Each side can have one or two layers of data. The amount of video a disc can hold depends on how much audio accompanies it and how heavily the video and audio are compressed. A single-layer disc typically holds just over two hours of video, although it's possible to put about eight hours of VHS-quality video or 160 hours of audio on a single layer.

The list below shows variations of DVD. SS/DS means single-/double-sided, SL/DL/ML means single-/dual-/mixed-layer (mixed means single layer on one side, double layer on the other side), gig means gigabytes, G means billions of bytes. For reference, a CD-ROM holds about 650 megabytes, which is 0.64 gigabytes or 0.68 billion bytes.

The DVD-ROM and DVD-Video formats are well established and completely standardized. Unfortunately, things are not so clear-cut on the recordable side. There are six recordable versions of DVD-ROM: DVD-R, DVD+R, DVD-RAM, DVD-RW, and DVD+RW. DVD-R can record data, while DVD-RAM, DVD-RW, and DVD+RW can be rewritten a thousand times or more. Each format is available as a computer drive for recording data. The three rewritable formats are also being used by consumer companies for home video recorders that will be available later in 2000.

DVD-R:
Capacity: 4.7GB single side
Compatibility: Highly compatible with home DVD players

The advantage of DVD-R is that the media is compatible with many existing DVD-ROM drives and DVD-Video players, since it uses organic dye polymer technology, like CD-R.

DVD+RW / DVD+R:
Capacity: 4.7GB single side
Compatibility: Readable in many existing DVD-Video players and DVD-ROM drives

DVD+RW is an erasable format based on CD-RW technology which became available in late 2001. DVD+RW is supported by Philips, Sony, Hewlett-Packard, Dell, Ricoh, Yamaha, and others. DVD+RW drives read DVD-ROMs and CDs, and usually read DVD-Rs and DVD-RWs, but do not read or write DVD-RAM discs.

The DVD+RW format uses phase-change media with a high-frequency wobbled groove that allows it to eliminate linking sectors. This, plus the option of no defect management, allows DVD+RW discs to be written in a way that is compatible with many existing DVD readers.

DVD+RW drives also write CD-Rs and CD-RWs. DVD+RW discs, which hold 4.7 billion bytes per side, are readable in many existing DVD-Video players and DVD-ROM drives. (They run into the same reflectivity and disc format recognition problems as DVD-RW.) DVD+RW media can be rewritten about 1,000 times.

DVD+RW media is being produced by CMC Magnetics, Hewlett-Packard, MCC/Verbatim, Memorex, Mitsubishi, Optodisc, Philips, Ricoh, Ritek, and Sony.

DVD+R is a write-once variation of DVD+RW, which appeared in mid 2002. It's a dye-based medium, like DVD-R, so it has similar compatibility as DVD-R.

DVD-RW:
Capacity: 4.7GB single side
Compatibility: Playable in many DVD drives and players.

DVD-RW (formerly DVD-R/W and also briefly known as DVD-ER) is a phase-change erasable format. Developed by Pioneer based on DVD-R, DVD-RW is playable in many DVD drives and players. (Some drives and players are confused by DVD-RW media's lower reflectivity into thinking it's a dual-layer disc. In other cases the drive or player doesn't recognize the disc format code and doesn't even try to read the disc. Simple firmware upgrades can solve both problems.) DVD-RW discs can be rewritten about 1,000 times. DVD-RW is primarily supported by Pioneer.

DVD-RAM:
Capacity: 4.7GB / 9.4GB single side and double sided
Compatibility: Not compatible with most DVD-ROM drives and DVD-Video players.

DVD-RAM is the best suited of the writable DVD formats for use in computers, because of its defect management and zoned CLV format for rapid access. However, it's not compatible with most drives and players Think of it as a removable hard disk that can also read DVD-ROM discs. DVD-RAM is supported by Panasonic, Toshiba, Hitachi, and others. Single-sided DVD-RAM discs come with or without cartridges. There are two types of cartridges: type 1 is sealed, type 2 allows the disc to be removed. Discs can only be written while in the cartridge. Double-sided DVD-RAM discs were initially available in sealed cartridges only, but now come in removable versions as well. DVD-RAM can be rewritten more than 100,000 times, and the discs are expected to last at least 30 years.

Here is a summary of recordable DVD compatibility between Players (units) and Media (discs). For simplicity, "doesn't write" is implied if not otherwise specified:

	DVD unit	DVD-R(G) unit	DVD-R(A) unit	DVD-RW unit	DVD-RAM unit	DVD+RW unit
DVD-ROM disc	reads	reads	reads	reads	reads	reads
DVD-R(G) disc	routinely reads	reads, writes	reads	reads, writes	reads	reads
DVD-R(A) disc	routinely reads	reads	reads, writes	reads	reads	reads
DVD-RW disc	usually reads	reads	reads	reads, writes	usually reads	usually reads
DVD-RAM disc	rarely reads	doesn't read	doesn't read	doesn't read	reads, writes	doesn't read
DVD+RW disc	usually reads	usually reads	usually reads	routinely reads	usually reads	reads, writes
DVD+R disc	routinely reads	routinely reads	routinely reads	routinely reads	routinely reads	reads, may write

For much more in depth detail of DVD formats and technical information click HERE.

Most DVD PCs can play DVD movies. In addition to the drive, the computer must have the proper hardware or software to decode MPEG-2 video and Dolby Digital audio. Good-quality software-only playback requires at least a 350-MHz Pentium II or a Mac G4. Hardware upgrade kits can be purchased for existing computers.

Apple QuickTime 4 is partially ready for DVD-Video and MPEG-2 but does not yet have full decoding or DVD-Video playback support for general DVD applications. Macintosh G4s come standard with DVD-ROM or DVD-RAM drives. The G4s use the Velocity Engine portion of the PowerPC chip for video and audio decoding. Some models of the iMac, PowerBook, and G3 lines can be ordered with DVD-ROM drives and hardware decoders. A few DVD-ROM upgrade kits and decoder cards are available.

Computers have the potential to produce better video than set-top DVD players by using progressive display and higher scan rates. Not all computers live up to this potential, but a PC with a good decoder connected to a large VGA monitor or video projector can provide picture quality far beyond a standard DVD player and TV. If you want to hook a DVD computer to a standard TV, the decoder card or the VGA card must have a TV output (composite video or s-video).

Alternatively, you can connect a scan converter to the VGA output. The quality of the video will depend on the decoder, the TV encoder chip, and other factors, but will usually be a little inferior to a good consumer DVD player. If the decoder card or the sound card has Dolby Digital or DTS output, you can connect it to your A/V receiver to get multichannel audio.

What’s on a DVD?

If you have purchased a DVD that you want to copy, you can put it in your DVD-ROM drive to check out its contents. On the disc you will find several folders with files in it. Normally you should always see a VIDEO_TS and AUDIO_TS folder. The AUDIO_TS folder is used to store DVD Audio, the VIDEO_TS to store DVD Movies.

We will be focusing on a movie DVD, so we’ll enter the VIDEO_TS folder. In this folder you will find .VOB .BUP and .IFO files. The VOB file contains the actual movie files. This is a MPEG-2 encoded file. Simplified is MPEG-2 is a method of compression for movies, just like MP3 files are compress audio. The file contains also audio, normally this should also be a compressed format. Mainly it is an improved form of MP3, named AC-3. Besides that contain the .VOB files the subtitles and multiple camera angles.

The .IFO files are the information files, used by your DVD playing device. It gives the DVD player information on what .VOB files to load and when. E.g. when to start a new chapter. The .BUP files are simply a backup of the IFO files and generally have no use, they will only be used when an .IFO files become unreadable somehow.

Let’s copy those files!

You would think it would be as easy as copying these files to a folder on your hard disk and then burn them to a recordable DVD, but unfortunately they didn’t make it that easy. The files copied will contain useless data and your copy will not work,

DVD movies are protected with the Content Scrambling System (CSS), a protection developed and adopted by the Hollywood Studios. It simply protects them from pirates who want to make copies to sell. Simplified the protection encrypts the data on a DVD and requires a special key to decrypt it. DVD playing software developers have received such a key from the studios and therefore their software is able to read the information, but unfortunately the studios don’t hand out keys to anyone else.

However the protection has proven to be weak and has been beaten by many applications. Most of them are based on the software DeCSS of which you might have heard due the many lawsuits that try to forbid the software. The software is illegal in many countries. Removing the DeCSS protection and getting the movies to e.g. a hard drive is mainly referred to as ripping. Later on we will discuss the software available for ripping. Besides CSS movie sometimes also contain a protection developed by Macrovision, this is also on many VHS tapes, software that is able to remove CSS, will also easily remove this Macrovision protection.

Another problem is that if you are planning to record it to a recordable DVD, it simply won’t fit. Why doesn’t it fit? Currently DVD recordables can only contain about 4.7 (actually it’s 4.38) Gigabytes of data, they are generally referred to as DVD-5 (4.7 ~ 5). The movie you have purchased might contain a lot more Gigabytes, many movies are released with up to about 9 Gigabytes of data (DVD-9), you will understand that a DVD-9 movie, will not fit on a DVD-5 disc. In order to make this happen there are three possibilities:

Sometimes you will need to make choice between them, sometimes you can combine these techniques. On the next page we will show you the best solutions and show you where to go when you want to create a backup.

Why can't I play movies copied to my hard drive?
Almost all movies are encrypted with CSS copy protection (see below). Decryption keys are stored in the normally inaccessible lead-in area of the disc. You'll usually get an error if you try to copy the contents of an encrypted DVD to a hard drive. Although if you have used a software player to play the movie it will have authenticated the disc in the drive, allowing you to copy without error, but the encryption keys will not be copied. If you try to play the copied VOB files, the decoder will request the keys from the DVD-ROM drive and will fail. You may get the message "Cannot play copy-protected files".

What are the copy protection issues?

Content Scrambling System (CSS):
Because of the potential for perfect digital copies, paranoid movie studios forced a deeper copy protection requirement into the DVD standard. Content Scrambling System (CSS) is a data encryption and authentication scheme intended to prevent copying video files directly from DVD-Video discs. CSS was developed primarily by Matsushita and Toshiba. Each CSS licensee is given a key from a master set of 400 keys that are stored on every CSS-encrypted disc. This allows a license to be revoked by removing its key from future discs. The CSS decryption algorithm exchanges keys with the drive unit to generate an encryption key that is then used to obfuscate the exchange of disc keys and title keys that are needed to decrypt data from the disc. DVD players have CSS circuitry that decrypts the data before it's decoded and displayed. On the computer side, DVD decoder hardware and software must include a CSS decryption module. All DVD-ROM drives have extra firmware to exchange authentication and decryption keys with the CSS module in the computer. Beginning in 2000, new DVD-ROM drives are required to support regional management in conjunction with CSS Makers of equipment used to display DVD-Video (drives, decoder chips, decoder software, display adapters, etc.) must license CSS.