An Asymmetric Speech Coding Algorithm Using Vector Quantization and Silence Deletion

Abstract

AbstractIn store‐and‐forward and multi‐media speech applications, e.g. in voice‐mail or when adding verbal comments to a document, the speech encoder can be allowed more time and higher complexity than in real‐time speech coding. Decoding however must be simple when a low‐cost terminal (e.g., a PC) is used. This kind of coding algorithm is called an asymmetric algorithm. Asymmetric algorithms exploit encoding delay to code the signal efficiently. An existing asymmetric coding algorithm is Vector Quantization (VQ). A new asymmetric algorithm is proposed, based on the coding of the time intervals between zero‐crossings (frames) using VQ and silence deletion. The algorithm takes advantage of the empirical fact that infinitely clipped speech retains its intelligibility. The algorithm has been implemented using software and its performance was evaluated.