chapter  3
46 Pages

Dolby Digital Audio Coding Standards

The evolution of digital audio delivery formats continues to bring profound changes to the consumer entertainment experience. Beginning with introduction of the compact disc (CD) in 1982, consumers have benefited from the analog to digital migration of music delivery formats. Today, the CD audio format remains a primary means for reproducing very high-quality audio. However, a variety of innovative and compelling new delivery channels for digital audio and video entertainment have become available. Many of these delivery channels are incapable of delivering stereo audio signals directly from CDs, not to mention multichannel audio programs with accompanying video. The CD format supports stereo audio playback with 16 bit per sample pulse code modulation (PCM) and a sample rate of 44.1 kHz. This results in a total bit-rate of 1.41 megabits per second (Mbps), which is prohibitively high for many existing and emerging entertainment applications. Digital audio compression is essential for reducing the CD audio bit-rate to an appropriate level for these new applications.