부산대학교 도서관

The quality of speech output in adaptive aperture coding 1 has been improved. by two refinements: (i) a code selection procedure based on formal error minimization rather than observations of aperture crossing, 1 and (ii) a llimple adaptive low-pass filtering operation based on adjacent sample correlation values., measured on a shortterm basis (typically once every 20 to 30 ms), We deecribe these refinementa with epecial reference to a 7-code aperture characterstic designed for an average output rate of 1.2 bits/sample, and speach inputs sampled at 8 and 12kHz. At corresponding bit rates (9.6 to 14.4 kb/s), adaptive aperture codining, in conjunction with a first-order adaptive predictor, constitutes a medium-complexity approach in time-domain coding, with an output speech quality that is less-than-toll but neverthless usefull in many applications. A natural application of aperture coding is for speech storage where variability of output bit rate is less objectionable than in transmission.