1148 Chapter 30
coarsely quantized. Analysis is carried out for both indi-
vidual video frames (spatial reduction) and series of
frames (temporal reduction). The video bit rate can be
considerably reduced without significant degradation of
the picture.
The video program is stored as 4:2:0 component
video (Y, R-Y, B-Y) with progressive scan and picture
resolution of 720 × 480 pixels. The picture quality of a
particular DVD-Video title is primarily determined by
the expertise of the picture encoding. The average output
bit rate of a DVD-Video player is about 4.7 Mbps.
30.7.1 Audio Contents
Both stereo and multichannel soundtracks are accom-
modated in the audio portion of the DVD-Video stan-
dard. There can be 1 to 8 independent channels of linear
PCM (LPCM), 1 to 6 channels of 5.1-channel Dolby
Digital (AC-3), or 1 to 8 channels (5.1 or 7.1) of
MPEG-2 AAC audio. A disc can also optionally employ
DTS, SDDS, or other audio coding. Dolby Digital is the
coding standard used for multichannel soundtracks in
the United States (Region 1). The Dolby Digital sam-
pling frequency is 48 kHz, the nominal output bit rate is
384 kbps, and the maximum bit rate is 448 kbps.
Optionally, DTS codes multichannel audio data at a
nominal bit rate of 1.4 Mbps. DTS can optionally be
used to code 1 to 8 channels of audio, at sampling fre-
quencies ranging from 8 kHz to 192 kHz. One DTS
layer at a sampling frequency of 44.1 kHz can hold up
to 74 min of 5.1-channel audio. MPEG-1 stereo audio is
sampled at 48 kHz with a maximum bit rate of
384 kbps. MPEG-2 multichannel audio (up to eight
channels) is also coded at 48 kHz; its maximum bit rate
is 912 kbps. NTSC titles nominally use Dolby Digital,
and PAL titles use MPEG-2 audio coding; however,
PAL titles can optionally use Dolby Digital coding.
DVD-Video titles carry a redundant LPCM sound-
track employing sampling rates of either 48 or 96 kHz
and word lengths of 16, 20, or 24 bits. These LPCM
configurations are supported: 16/48 (up to eight chan-
nels), 20/48 (up to six channels), 24/48 (up to five chan-
nels), 16/96 (up to four channels), 20/96 (up to three
channels), and 24/96 (up to two channels). The
maximum LPCM bit rate is 6.144 Mbps on a
DVD-Video. Various contents must be accommodated
on a DVD-Video. For example, with an average video
bit rate of 3.5 Mbps, there might be three audio sound-
tracks each at 0.384 Mbps, and 4 subtitles each at
0.01 Mbps, yielding a total bit rate of 4.692 Mbps.
Thus, in this example, a DVD-5 would hold a
133 minute program.
Discs contain regional coding flags so players will
only play certain regional discs. For example, a Region
2 (Europe and Japan) player will not play discs coded
for the North American (Region 1) market. In this way,
movie studios can control release of titles to different
global markets. Regional coding of discs is optional;
discs can carry multiple codes or no codes. Decoding
circuitry is mandatory on all players.
DVD-Video optionally employ the Content Scram-
bling System (CSS) copy protection system.
CSS-encoded content cannot be digitally copied
because software keys needed to deencrypt the data are
missing in any copy. Macrovision copy protection,
similar to that used in set-top boxes, can be employed to
prevent digital-to-analog copying of DVD-Video titles.30.8 DVD-AudioThe DVD-Audio specification describes a high-fidelity
audio storage medium supporting flexibility in the num-
bers of channels, sampling frequencies, word lengths,
and other features such as video elements. DVD-Audio
is principally used to code high-fidelity stereo and mul-
tichannel music programs using linear PCM (LPCM)
data. Development of DVD-Audio was influenced by
the International Steering Committee (ISC) representing
the interests of the major record labels.
DVD-Audio was designed for compatibility with
other DVD formats, some backward compatibility with
the CD format, and to achieve improved sound quality
and multichannel playback. Although the DVD-Video
format can provide high-quality audio (such as six chan-
nels at 48 kHz/20-bit audio), its maximum audio bit rate
of 6.144 Mbps cannot support the highest audio quality
levels. Thus DVD-Audio’s maximum bit rate was
increased to 9.6 Mbps. However, six channels of
96 kHz/24-bit audio exceeds the maximum bit rate and
high bit rates reduce playing time. Thus the Meridian
Lossless Packing (MLP) lossless compression algorithm
can be optionally employed to reduce bit rate, providing
high fidelity and long playing time. This option allows
storage of over 74 minutes of multichannel music on a
single data layer. All DVD-Audio must contain an
uncompressed or MLP-compressed LPCM version of
the DVD-Audio portion of the program. For added
compatibility with DVD-Video players, DVD-Audio
may also include video programs with Dolby Digital,
DTS, and/or LPCM tracks.