DVD Demystified

DVD Overview
74 minutes of super-fidelity multichannel audio or over 7 hours of CDquality
stereo audio.
Widescreen Movies
Television and movies shared the same rectangular shape until the early
1950s when movies began to get much wider. Television has stayed
unchanged until recently. Widescreen TVs are appearing slowly, and DVD
is bound to cause a huge jump in demand. Movies can be stored on DVD in
widescreen format to be shown on widescreen TVs close to the width envisioned
by the director. DVD includes techniques to show these widescreen
movies on regular televisions and straddles old and new television, since
HTDV is a widescreen format. These different aspect ratios are discussed in
detail in Chapter 3.
Multiple Surround Audio Tracks
159
The DVD-Video standard provides for up to eight soundtracks to support
multiple languages and supplemental audio. Each of these audio tracks can
include surround sound with 5.1 channels of discrete audio. 3 DVD surround-sound
audio uses Dolby Digital (AC-3) encoding, DTS Digital Surround,
or MPEG-2 audio encoding. The 5.1-channel digital tracks can be
downmixed by the player with Dolby Surround encoding for compatibility
with regular stereo systems and Dolby Pro Logic audio systems. An option
is also available for better-than-CD-quality linear PCM audio. Almost all
DVD players include digital audio connections for high-quality output.
The usefulness of multiple audio tracks was discovered when digital
audio was added to laserdiscs, leaving the old analog tracks free. Visionary
publishers such as Criterion used the analog tracks to include audio
commentary from directors and actors, musical sound tracks without
lyrics, foreign-language audio dubs, and other fascinating or obscure
audio tidbits.
DVD-Audio improves on the audio features of DVD-Video with higher
sampling rates for PCM and improved support for multichannel PCM audio
tracks and audio downmixing.
3 Discrete means that each channel is stored and reproduced separately rather than being mixed
together (as in Dolby Surround) or simulated. The .1 refers to a low-frequency effects (LFE) channel
that connects to a subwoofer. MPEG-2 and SDDS audio allow 7.1 channels, but this feature
is unlikely to be used for home products.