DVD Formats and Standards

As with the CD standards, the DVD standards are published in reference books produced mainly by the DVD Forum, but also by other companies.

The DVD-Video and DVD-ROM standards are pretty well established, but recordable DVD technology is still evolving. The standards situation for recordable DVD is more confusing than usual, especially because there are at least four different (and somewhat incompatible) recording formats! It remains to be seen which will have the best support and become the most popular, but so far the DVD-RW and DVD+RW formats are both very popular. However, DVD+RW looks to be by far the most promising for the future with higher speed, features that make it ideal for both video and data recording, higher compatibility with existing DVD players and drives, and finally Microsoft's endorsement via including support in upcoming versions of Windows. At this point, the only type of recordable DVD I recommend for both home DVD recorders and PC-based DVD recordable drives are units that conform to the DVD+RW format. That also includes DVD±R/RW drives (which support both formats in a single unit), making them essentially compatible with everything. I recommend avoiding drives that do not support the DVD+R/RW format.

With advancements coming in blue-light lasers, this capacity will be increased several-fold in the future with an HD-DVD format that can store up to 20GB per layer. Prototype players have already been shown by major manufacturers, although you shouldn't expect to see HD-DVD on the market just yet.

DVD drives are fully backward-compatible and as such are capable of playing today's CD-ROMs as well as audio CDs. When playing existing CDs, the performance of current models is equivalent to a 40x or faster CD-ROM drive. Therefore, users who currently own slower CD-ROM drives might want to consider a DVD drive instead of upgrading to a faster CD-ROM drive. Several manufacturers have announced plans to phase out their CD-ROM drive products in favor of DVD. DVD is rapidly making CD-ROMs obsolete in the same way that audio CDs displaced vinyl records in the 1980s. The only thing keeping the CD-ROM format alive is the battle between competing DVD recordable standards and the fact that CD-R and CD-RW are rapidly becoming the de facto replacements for the floppy drive.

The current crop of DVD drives features several improvements over the first-generation models of 1997. Those units were expensive, slow, and incompatible with either CD-R or CD-RW media. Many early units asked your overworked video card to try to double as an MPEG decoder to display DVD movies, with mediocre results in speed and image quality. As is often the case with "leading-edge" devices, their deficiencies make them eminently avoidable.

Many PC vendors have integrated DVD-ROM drives into their new high-end computers, usually as an option. Originally, most of these installations included an MPEG-2 decoder board for processing the compressed video on DVDs. This offloads the intensive MPEG calculations from the system processor and enables the display of full-screen, full-motion video on a PC. After processors crossed 400MHz in speed, performing MPEG-2 decoding reliably in software became possible, so any systems faster than that usually don't include a hardware decoder card.

Some manufacturers of video display adapters have begun to include MPEG decoder hardware on their products. These adapters are known as "DVD MPEG-2 accelerated" and call for some of the MPEG decoding tasks to be performed by software. Any software decoding involved in an MPEG solution places a greater burden on the main system processor and can therefore yield less satisfactory results on slower systems.

DIVX (Discontinued Standard)

DIVX (Digital Video Express) was a short-lived proprietary DVD format developed by Digital Video Express (a Hollywood law firm) and Circuit City. It was discontinued on June 16, 1999, less than a year after it was released.

The name now lives on as an open encoding standard for DVD video. However, this encoding standard actually has no relation to the original DIVX format other than the name.

DVD Drive Compatibility

When DVD drives first appeared on the market, they were touted to be fully backward-compatible with CD-ROM drives. Although that might be the case when reading commercially pressed CD-ROM discs, that was not necessarily true when reading CD-R or CD-RW media. Fortunately, the industry has responded with standards that let you know in advance how compatible your DVD drive will be. These standards are called MultiRead for computer-based drives and MultiPlay for consumer standalone devices, such as DVD-Video or CD-DA players.

DVD Movie Playback on a PC

Almost all DVD-ROM and rewritable DVD drives (except for some DVD-RAM drives) include a DVD playback program such as MyDVD or SoftDVD. These programs enable you to interact with a DVD movie the same way you would if it were being played through a DVD player.

However, if your video card doesn't have built-in MPEG-2 decoding, you might want to consider upgrading to a better video card that has this feature (all recent ATI and NVIDIA chipsets support MPEG-2 decoding in hardware) or install a separate MPEG-2 decoder. Hardware decoding is very important for best quality, particularly if your processor has a clock speed below 1GHz (it's possible with a 400MHz machine, but at least 1GHz is ideal).

If you are using a hardware decoder, it requires an open PCI expansion slot, as well as an interrupt request (IRQ) resource from your system. Also, to view the movies on your PC's display, you must somehow connect the decoder card to your existing video card. This can be accomplished via an internal connection to the card, or it can use a loop-through connection to the monitor port on the back of the card. Some video cards include MPEG-2 decoders (players) built in. The table below compares MPEG decoder hardware (built in to a separate card or integrated into a video card's 3D accelerator chip) with MPEG player.