Voice over IP systems with speech bitrate adaptation based on MPEG-4 wideband CELP

Abstract

This paper proposes bitrate adaptation schemes for real-time voice over IP applications, based on multirate and scalable coding capabilities in MPEG-4 CELP. For IP telephony applications, the adaptation scheme based on multi-rate coding is utilized to achieve the best coding quality at a given bitrate. For broadcast applications, the scalable CELP coder produces a layered bitstream and the bitrate control at IP routers determines the number of bitstream layers depending on the network throughputs. Performance evaluation of bitrate adaptation using the MPEG-4 wideband CELP coder is presented.