[Audio functions of DVD-Video]

Dolby Digital(AC-3) is an audio compression technology that enables 5.1-channel digital surround sound in which each channel is discrete.

With 5.1-channel digital surround technology, five discrete channels are available for storage and playback of sound. They consist of two front channels, two rear channels and one center channel which is mainly used for narration.These, plus the 0.1 sub-woofer for heavy bass, add up to a grand total of 5.1 channels.

This system enables sound to be moved back and forth between front and rear, and left and right. Everything is possible, from the ultra-bass rumbling of a volcano or the footsteps of an approaching dinosaur, to the high-pitched swish of an object hurtling through space.

Besides the 5.1 channel digital surround sound, there are various other possibilities. With AC-3 technology, a DVD-Video title can be produced in 2-channel stereo, 3-channel stereo by splicing the center channel between two other channels, or 4-channel stereo by adding rear surround to the 3-channel configuration.

Dolby Digital(AC-3) technology enhances sound separation, ambience and sound direction. With conventional Dolby ProLogic, 4-channel sound including the surround channel is recorded in two channels by matrix processing, andduring playback a decoder is used to reconstitute the four channels.

Thus, Dolby ProLogic does not provide discrete channels and the rear channel is monaural. As a result, with Dolby ProLogic it is possible to reproduce the movement of sound between front and rear, but impossible to reproduce that between right and left at the rear. Furthermore, frequencies above 7kHz are deleted from the rear channel. Dolby Digital(AC-3) technology transcends these limitations, bringing movie theater-quality dynamic surround sound into the home.