Progress in Speech and Audio Coding

Abstract

Progress in speech and audio coding is presented, focusing on the technology of linear predictive coding (LPC), which has played important roles in various processing schemes for speech and audio signals in general. From the first, LPC has been used for speech synthesis and telephone bandwidth speech coding, since it was found to be well suited to represent the characteristics of the vocal tract. In contrast, typical audio coding schemes have not used LPC. However, because of the needs of a low bitrate and the unification of speech and audio coding, LPC has come to be used for representing spectral information in audio coding as well. In line with this trend, two new standard coding schemes are introduced: audio lossless coding, MPEG-4 ALS, for digital broadcasting, and 3GPP EVS for recent cellular telephones.