High quality coding of wideband speech at 24 kbit/s

Abstract

This paper proposes a Wideband-CELP-Coding scheme (bandwidth 7kHz) at 24 kbit/s. The codec introduces a delay of just 10 ms. This fulfills the requirements of a possible codec candidate for wideband speech coding within DECT or video applications [I]. The analysis-by-synthesis structure of the proposed Wideband-CELP-Codec includes an alternative LPC analysis concept, where the autocorrelation function is calculated recursively [2]. This special LPC scheme provides an improved speech quality and a reduction of computational complexity in comparison to conventional algorithms for the LPC analysis. In addition a stochastic sparse codebook with extremely low computational effort is presented, comparable to the one presented in [12] resulting in a neglectable amount of storage. The CCITT G.722 standard was applied as reference codec, in order to compare the new coding scheme in terms of subjective quality. With the proposed Wideband-CELP a speech quality is achieved, which is equivalent to the reference codec op erating at 56 kbit/s.