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Techno Tidbits and Problem-solving
94
En
Dolby
Dolby Digital
Dolby Digital is a discrete digital surround format used for multichannel surround sound. It was developed after the
Dolby Surround System and Dolby Pro Logic Surround System. Dolby Digital is a high quality digital sound format
that is used by many theatrical film releases.
Other features include:
1) Downmixing on playback for compatibility with mono, stereo, Dolby Pro Logic and 5.1 channel audio.
2) A wide range of bitrates and channels.
3) Decoding dynamic range information and adjusting the dialog level in the soundtrack (called Dialog
Normalization, see below for more information).
Dialog Normalization
When a Dolby Digital soundtrack is played back the Dialog Normalization function of the receiver activates
automatically. Dialog Normalization is a Dolby Digital function that establishes the average dialog level for the
program source being played. If the receiver’s level does not match the average dialog level, first you see “DIAL
NORM” and “OFFSET +4 dB” (as an example) appear in the receiver’s display. In this example, the number +4 dB is
the difference between the receiver’s gain structure and the Dolby Digital average dialog level. To match the average
dialog level, subtract or add the OFFSET level. For example, if the OFFSET level is +4 dB, the amplifier’s output is 4
dB over the average recorded level.
Dolby Pro Logic II
Dolby Pro Logic II is an improved version of Dolby Pro Logic technology with extended matrix decoding technology
that can create 5.1 channel sound from two channel sources. Dolby Pro Logic II creates basic 5 channel sound by
using the innovative “steering logic” circuit. Therefore when listening to typical two-channel sources like CD, the
listener can enjoy a richer spatial effect. When using software encoded with Dolby Surround, this decoding system
affords the listener an improved surround experience with greater sound detail.
Chart Comparing Dolby Pro Logic and Dolby Pro Logic II
Dolby Digital Surround EX
This new recording technology is able to play 6.1 channel sound and was developed in a collaboration between
Dolby Laboratories and Lucasfilm, Ltd. for the film “Star Wars: The First Episode”, the first movie ever to be made
with Dolby Digital Surround EX technology. In a movie theater this format affords the listener vivid surround sound
experience replete with the effect of sounds flying overhead, even for those seated towards the sides of the theater.
Dolby Digital Surround EX contains surround back channels which are dubbed into the soundtrack in studio. The
channels are encoded into the left and right channels of the soundtrack so this format can be compatible with
Dolby Digital 5.1 channel decoding. For a list of movies that contain Dolby Digital Surround EX soundtracks see
Dolby website at: http://www.dolby.com
DTS
DTS
In this system, 6 channels of digital sound are recorded on CD-ROM. 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. For this reason, the format is being introduced in more and more movie theaters, and is being adopted
for home use as DTS Digital Surround. When used with movies it’s called DTS-LD DVD and for music software (5.1
channel CD) as DTS-CD.
Pro Logic Pro Logic II
Effective sound source Dolby Surround encoded sources All two channel stereo sources
Surround Sound Mono Stereo
Frequency Range Surround within 7kHz All Channels/Full Range
Techno Tidbits and Problem-solving
00_VSX-AX3.book Page 94 Monday, May 19, 2003 1:05 PM