Far too many people present themselves as DVD experts without knowing the
first thing about DVD. This is my response to the myths generated by helpful but
clueless people. Suggestions are welcome.
These myths are debunked by facts. Dispute them at your peril. Read the DVD FAQ
for more info.
[Last updated July 21, 2001.]
- Not HDTV compatible.
Current DVD players are compatible with HDTVs in the same way VCRs,
camcorders, and laserdisc players are compatible. In order to take
take advantage of the digital nature and progressive scan of HDTV, new
DVD players will be required. These players will make current discs
look even better on HDTVs, but won't provide full HDTV resolution.
Eventually a new "HD-DVD" format will appear, based on blue lasers.
The new format will require new discs and new players, but the players will play old
DVD discs and CDs.
- DVD is unfinished, with competing formats.
The DVD-ROM and DVD-Video standards are finalized as single formats. There
were once two competing formats (SD and MMCD) but they were combined to form
DVD back in 1995. DVD-Audio is also finalized. There is no reason to delay
buying DVD players or discs because of rumors that it might change. On the
other hand, there are a number of competing, incompatible DVD recording
formats (DVD-R/RW, DVD+R/RW, and DVD-RAM). It will take a while before the
recordable DVD mess gets sorted out.
- 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).
- Audio is only 12 bits.
This myth was started by an article in Widescreen Review magazine that 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.
- 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.
- 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
- Playing CDs is harmful.
Playing an audio CD in a DVD player will not hurt the disc or the player.
Some players use a single laser for reading DVDs and CDs, while others have
separate lasers, but in either case there is nothing about the lasers that
can damage a CD, nor is there anything about a CD that can affect the
- Digital artifacts.
Many 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 exhibit few visible compression
artifacts on a properly configured system. If you think otherwise, you are
probably misinterpreting what you see.
- Players can't read dual-layer discs.
All DVD-Video players and all DVD-ROM drives are required to play dual-layer discs.
A few faulty units might have problems reading dual-layer discs. Dual-sided discs must be flipped over by hand.
(Only a few multi-disc changers can flip discs automatically.)
- DVD is a worldwide standard.
In addition to regional codes that can be used to prevent playback in
different areas, DVD uses different formats for NTSC or PAL playback. Almost
no US players can play PAL DVDs. All PAL players can play both PAL
and NTSC DVDs, but only on a 60-Hz-capable PAL TV or a multistandard TV.
Most DVD-equipped computers can play both NTSC and PAL discs.
Jim (the Frog)
Author of DVD Demystified and the