Digital Versatile Disk (Dvd) Technology; Audio Features Of Dvd-Video - Compaq Evo D510 e-pc Technical Reference Manual

Digital Versatile Disk (DVD) Technology

Digital Versatile Disc (DVD) is a medium for the distribution of from 4.7 to 17 GB of digital data
on a 120 mm (4.75 inch) disc. This huge volume of data (CD-ROMs can store 680 MB) can be
used to store up to nine hours of studio quality video and multi-channel surround-sound audio,
highly interactive multimedia computer programs, 30 hours of CD-quality audio, or anything
else that can be represented as digital data.
A DVD looks like a CD-ROM: it is a silvery disc, 4.75 inches in diameter, with a hole in the
center. Like a CD, data is recorded on the disc in a spiral trail of tiny pits, and the discs are read
using a laser beam. The DVD's larger capacity is achieved by making the pits smaller and the
spiral tighter, and by recording the data in as many as four layers, two on each side of the disc.
To read these tightly packed discs, lasers that produce a shorter wavelength beam of light are
required, as are more accurate aiming and focusing mechanisms. In fact, the focusing mechanism
is the technology that allows data to be recorded on two layers. To read the second layer, the
reader simply focuses the laser a little deeper into the disc, where the second layer of data is
recorded.
Not only are two layer discs possible, but so are double-sided discs. The availability of
four layers is what gives DVD its 17 GB capacity.
Diameter
Thickness
Track Pitch
Minimum Pit Length
Laser Wavelength
Data Capacity (per layer)
Layers

Audio features of DVD-Video

A DVD-Video disc can have up to 8 audio tracks (streams). Each track can be in one of
three formats:
■
Dolby Digital (Dolby AC-3): 1 to 5.1 channels
■
MPEG-2 audio: 1 to 5.1 or 7.1 channels
■
LPCM: 1 to 8 channels
Dolby Digital is multi-channel digital audio, using lossy AC-3 coding technology from original
PCM with a sample rate of 48 kHz at up to 24 bits. The bitrate is 64 kbps to 448 kbps, with
384 being the normal rate for 5.1 channels and 192 being the normal rate for stereo (with or
without surround encoding).
Technical Reference Guide
DVD
120 mm
0.6 mm
0.74 nm
0.40 nm
640 nm
4.7 GB
1, 2, 4
System Features
CD
120 mm
1.2 mm
1.6 nm
0.834 nm
780 nm
0.68 GB
1
2–13