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5.7.8 Audio Glossary
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Dolby
Surround is an audio encoding process. When a Dolby
soundtrack is produced, four channels of audio information — left, center,
right, and surround — are matrix-encoded onto two audio tracks. These two
tracks are then recorded onto stereo program sources, like videotapes and
TV broadcasts.
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Dolby
Digital 5:1 (AC-3) is an audio encoding process that simulates the
illusion of total surround sound. The system consists of five speakers and
one bass unit, hence the name 5:1. Normally, the listener is faced by two
front speakers and surrounded by two rear speakers; both pair of speakers
supply full stereo output. An additional, center speaker, facing the listener, is
mainly used for dialogue between actors and actresses.
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The Dolby
Digital 5:1 AC-3 coder is designed to take advantage of natural
human auditory masking. AC-3 coding is essentially a very selective and
powerful noise reduction filter. The coder system divides the audio spectrum
of each channel into narrow frequency bands of precise proportions, each
one optimized with respect to the innate frequency selectivity of human
hearing. Coding noise is filtered out by matching its frequency to the "blind
spots" of human hearing. By reducing coding noise, the sound quality of the
original signal can be preserved and enhanced.
S/PDIF: S/PDIF (Sony/Philips Digital Interface) is a standard audio transfer
file format. It is usually built-in to the digital processors of audio equipment
such as DAT recorders or audio processing devices. It facilitates transfer of
audio data from one file to another without conversion to and from the analog
format, which could degrade signal quality. The most common connector
used with an S/PDIF interface is the RCA jack, the same one used for many
consumer audio-visual products. An optical connector is also available.
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Chapter 5: Software reference
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Surround
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