Dolby^® Digital

In thousands of cinemas and millions of homes worldwide, Dolby Digital is the reigning standard for surround sound technology in general and 5.1-channel surround sound in particular.

Dolby Digital is a highly sophisticated and versatile audio encoding/decoding technology. Dolby Digital technology can transmit mono, stereo (two-channel), or up to 5.1-channel surround sound (discrete* multichannel audio).

Figure 1 How Dolby Digital Works

The superior coding efficiency of Dolby Digital-and its ability to deliver high-quality discrete multichannel audio without compromising video quality-has made it the designated audio standard for DVD worldwide

Dolby Digital is also the preferred multichannel audio standard for direct broadcast direct to home satellite and digital cable systems. Nearly 60 million digital cable and satellite set-top boxes are currently in use worldwide supported by over 30 million audio/video receivers equipped with 5.1-channel Dolby Digital decoding. Virtually every DVD-Video player sold today offers a two-channel mixdown of the Dolby Digital 5.1 movie soundtrack as well as a digital output for connection to a 5.1-channel audio/video receiver.

In the film industry, the Dolby Digital soundtrack is optically encoded right on the filmstrip, in the space between the sprocket holes. Placing the soundtrack directly on the film allows it to coexist with the analog track, a cost-effective and simple solution for film distributors and theatre owners. The sprocket hole area has also proven highly resistant to wear and tear, so that a soundtrack encoded in Dolby Digital will remain free of pops and hiss for the useful life of the print.

* The sound information contained in each of the six available channels is distinct and independent. These six channels are described as a "5.1-channel" system, because there are five full-bandwidth channels with 3 Hz to 20 kHz frequency range for Front Left and Right, Center, and Surround, plus one "Low Frequency Effects" (LFE) subwoofer channel devoted to frequencies from 3 to 120 Hz.

Figure 2 Dolby Stereo	Figure 3 Dolby Digital 5.1