Perceptual transform coding of wideband stereo signals

The author reports on the extension of the entropy-coded perceptual transform coder (ECPTC) to stereo signals. The stereo ECPTC exploits both the redundancy in the stereo signal and the effects of acoustic mixing in the listening environment in order to encode the stereo signal at a bit rate much less than twice that for a monophonic signal. This coder uses the perceptual threshold developed by the author (IEEE J. Selected Areas in Commun. vol.6, no.2, p.314-23, Feb. 1988) along with a noiseless compression scheme to provide a bit-rate reduction of approximately one third compared to that for two independent monophonic channels. Typical rates available from the coder are 64 kb/s for a 6.6-kHz bandwidth, 14-kHz sampling rate transparent monophonic channel, 128 kb/s for a 15-kHz bandwidth, 32-kHz sampling rate stereo channel with FM or better quality, and 192 kb/s for a 20-kHz bandwidth, 44.1-kHz sampling rate stereo channel with perceived quality equal to that of the original signal. The 64-kb/s, 128-kb/s, and 192-kb/s rates correspond to ISDN (integrated services digital network) 1B, 2B, and 3B rates respectively, suggesting applications within the ISDN framework