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En
11 Techno Know How
Dolby Digital and Dolby Surround
Dolby Digital is the most widely used system to record soundtracks on DVDs and other media. It's a sound
compression format which records the sound of 6 channels of the theater surround system (Dolby Digital) on a
movie film digital track. Of the 6 channels, the subwoofer channel is intended for bass only, and because the
frequency range is smaller than a main channel, the overall soundtrack is called 5.1 channels.
Dolby Digital is the name of the Dolby surround multichannel digital system that was developed after the Dolby
Surround System and Dolby Pro Logic Surround System.
Dolby Digital is also known as the 5.1 channel system. It is equipped with 5 channels (front left, front right,
center, surround left, surround right) in the frequency range from 20 Hz to 20 kHz and an independent Low
Frequency Effect (LFE) channel. The subwoofer channel is also called Low Frequency Effect (LFE).
This channel can be used with a powered subwoofer to get strong bass sounds.
DTS
DTS is another widely used system to record soundtracks on DVDs and other media. It has been adopted as a
sound recording format in the latest movie theaters since the release of “JURASSIC PARK” in 1993, and has a
good reputation for high quality sound and dynamic surround effects.
In this system, 6 channels of digital sound are recorded on CD-ROM, rather than on the film. DTS adopts a
simultaneous playback format. With a low rate of compression of sound signals and a high rate of transmittance,
a higher sound quality format is produced. Also, unlike the process of recording digital sounds on film directly,
the only components required are a CD-ROM player as might be used with a personal computer and a DTS
processor, and therefore less investment is required than with other formats. For this reason, the format is being
introduced in more and more movie theaters, and is being adopted in home movie software (DVD, LD) and
music software (5.1 channel CD).
Digital Audio Formats
Home theater uses various types of methods to encode the sound on to the digital sources and these are known as
digital formats. The most common digital formats are explained below.
No. of recorded channels
No. of playback channels
Playback channel structure
Sound processing
Rear (Surround) high
frequency playback limit
Other
Dolby Digital
5.1 channels (Max.)
5.1 channels (Max.)
Front Left, Front Right, Center,
Surround Left, Surround Right,
Subwoofer
Digital discrete processing
20,000 Hz
•5.1 completely independent
channels
•High dynamic range
•Stable position, high phase
characteristics, and advanced
surround effects reproduction
•High efficiency
(Compression rate of about one-
tenth)
Dolby Pro Logic
Surround
2 channels
4 channels
Front Left, Front
Right, Center,
Surround
Analog matrix
processing
7,000 Hz
DTS
5.1 channels (Max.)
5.1 channels (Max.)
Front Left, Front Right, Center,
Surround Left, Surround Right,
Subwoofer
Digital discrete processing
20,000 Hz
•5.1 completely independent
channels
•High dynamic range
•Stable position, high phase
characteristics, and advanced
surround effects reproduction
•Low compression rate
(about one-fourth), high quality
sound
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R
LANGUAGE
CAPTIONS
SUBTITLES
English
Captioned
5.1
SURROUND
5.1
SURROUND
Understanding DVD Packaging
DVD packaging usually states what sound formats are included on the DVD.
The diagram here shows what you might see on a typical DVD box. The terms
used (Dolby Digital, etc.) are explained in the following sections.