DVD Basic Questions

How should I clean and care for DVDs?

Since DVDs are read by a laser, they are resistant—to a point—to fingerprints, dust, smudges, and scratches. However, surface contaminants and scratches can cause data errors. On a video player, the effect of data errors ranges from minor video artifacts to frame skipping to complete unplayability. So it's a good idea to take care of your discs. In general treat them the same way as you would a CD.

Your player can't be harmed by a scratched or dirty disc, unless there are globs of nasty substances on it that might actually hit the lens. Still, it's best to keep your discs clean, which will also keep the inside of your player clean. Never attempt to play a cracked disc, as it could shatter and damage the player. It doesn't hurt to leave the disc in the player (even if it's paused and still spinning), but leaving it running unattended for days on end might not be a good idea.

In general, there's no need to clean the lens on your player, since the air moved by the rotating disc keeps it clean. However, if you commonly use a lens cleaning disc in your CD player, you may want to do the same with your DVD player. We recommend only using a cleaning disc designed for DVD players, since there are
minor differences in lens positioning. Handle only at the hub or outer edge. Don't touch the shiny surface with your popcorn-greasy fingers.

Is CD audio (CD-DA) compatible with DVD?

Yes. All DVD players and drives will read audio CDs (Red Book). This is not actually required by the DVD spec, but so far all manufacturers have made their DVD hardware read CDs.

On the other hand, you can't play a DVD in a CD player. (The pits are smaller, the tracks are closer together, the data layer is a different distance from the surface, the modulation is different, the error correction coding is new, etc.) Also, you can't put CD audio data onto a DVD and have it play in DVD players. (Red Book audio frames are different than DVD data sectors.)

DVD Myths

When talking to people about DVD, it appears that strangely, some myths seem to have manifested themselves in people’s minds, both, DVD owners and non-owners. The following section will shed some light on some of the most common myths about DVD, countering them with factual explanations.

1. Not HDTV compatible.
Current DVD players are compatible with HDTVs in the same way VCRs, camcorders, and laserdisc players are compatible.

2. Dolby Digital is 5.1 channels.
Dolby Digital (formerly called AC-3) carries from 1 to 5 channels of compressed digital audio, with an optional ".1" low-frequency effects (LFE) channel. The Dolby Digital track does not have to include 5.1 channels. It may be mono or stereo, and the stereo may or may not be Dolby Surround encoded (for playback on a system with a Dolby Pro Logic decoder).

3. Audio is only 12 bits.
This myth was started by Widescreen Review magazine, which attempted to equate jitter in DVD players to a reduced audio resolution. DVD audio can be either 16, 20, or 24 bits. Jitter does not reduce the number of bits. There are many kinds of jitter. Jitter in the channel signal is accounted for in the readout circuitry. Jitter in the digital audio output is related to the audio circuitry and is independent of the DVD format. It's true that jitter at different stages can reduce audio quality, but comparing it to a 12-bit sample size is naive and inaccurate. Numerous reviews indicate that most DVD players sound as good or better than most CD transports.

4. Audio level too low.
In truth the audio level is too high on everything else. Movie soundtracks are extremely dynamic, ranging from near silence to intense explosions. In order to support an increased dynamic range and hit peaks (near the 2V RMS limit) without distortion, the average sound level must be lower. This is why the line volume from DVD players is lower than from almost all other sources.

5. 133 minutes per side.
This is a meaninglessly exact figure. A single-layer disc can easily hold 150 minutes at the typical average video data rate if there's only one audio track. Lowering the data rate slightly can accommodate over three hours on a single layer. Dual-layer discs can hold over four hours on one side.

6. Digital artifacts.
Almost all reports of "artifacts" on DVD turn out on examination to have nothing to do with MPEG compression. Artifacts come from many sources: film problems, bad video transfer, improper TV settings, bad video connections, electrical interference, player faults, disc read errors, etc. Some of these can be corrected by adjusting the TV or cleaning the disc. Most DVDs have very few visible compression artifacts. If you think otherwise, you are misinterpreting what you see.

7. Players can't read dual-layer discs.
All DVD-Video players and all DVD-ROM drives play dual-layer discs. Dual-sided discs must be flipped over by hand. (There are no side-flipping DVD players.)