13Additional information
Surround sound formats
Below is a brief description of the main surround sound formats you’ll find on DVDs, satellite, cable and terrestrial broadcasts, and video cassettes.
Dolby
The Dolby technologies are explained below. See
www.dolby.com for more detailed information.
Dolby Digital
Dolby Digital is a multichannel digital audio coding system widely used in cinemas, and in the home for DVD and digital broadcast soundtracks. It can deliver up to six discrete audio channels, comprising five full range channels and a special LFE (low frequency effects) channel used mainly for deep, rumbling sound effects; hence the term
In addition to the format features above, Dolby Digital decoders offer downmixing for compatibility with mono, stereo and Dolby Pro Logic audio from a number of bit rates and channels. Another feature, called Dialog Normalization, attenuates programs based on the average level of dialog in a program relative to its peak level (also known as Dialnorm) in order to achieve uniform playback level.
Dolby Surround is an encoding system which embeds surround sound information within a stereo soundtrack, which a Dolby Pro Logic decoder can then use for enhanced surround listening with greater sound detail.
Dolby Digital Plus
Dolby Digital Plus is the
Dolby Digital Plus delivers
It also features
Dolby Digital Surround EX
Dolby Digital Surround EX (the EX stands for EXtended) is an extension of Dolby Digital encoding whereby a surround back channel is matrixed into the surround left/ right channels for 6.1 channel playback. This allows for compatibility with Dolby Digital 5.1 channel decoding, as well as for decoding using Dolby Digital EX.
Dolby Pro Logic IIx and Dolby Surround
Dolby Pro Logic IIx is an improved version of the Dolby Pro Logic II (and Dolby Pro Logic) decoding system. Using the innovative “steering logic” circuit, this system extracts surround sound from sources as follows:
•Dolby Pro Logic – 4.1 channel sound (mono surround) from any stereo source
•Dolby Pro Logic II – 5.1 channel sound (stereo surround) from any stereo source
•Dolby Pro Logic IIx – 6.1 or 7.1 channel sound (stereo surround and surround back) from two channel or 5.1 (and 6.1) channel sources
With two channel sources, the “.1” subwoofer channel is generated by bass management in the receiver.
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Dolby TrueHD
Dolby TrueHD is the
It supports bit rates of up to 18 Mbps and records up to 8
*HD DVD and
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