A robust 384 kbit/s stereo HiFi audio codec for ISDN applications

A robust stereo HiFi audio codec designed for 384 kb/s ISDN (integrated services digital network) subrate (H0) channel applications has been developed. The codec is based on subband ADPCM (adaptive differential pulse code modulation). In order to realize high coding quality, a new adaptive bit assignment function is introduced which needs no side-information transmission. Moreover, the coding algorithm brings about the robustness to withstand transmission bit errors in actual transmission environments such as satellite communications, where conventional adaptive bit assignment is inherently inferior. The codec is implemented using floating-point LSI signal processors. Subjective test results show that the coding quality is comparable to that of compact discs. The proposed algorithm can be applied to a basic ISDN channel by limiting the signal bandwidth to 15 kHz and transmitting FM-quality monophonic signals at 128 kb/s.<>