Variable bit rate ADPCM via arithmetic coding

section, leading to the introduction of our proposed variable bit rate system. After some coverage of the performance of the system with a standard linear predictor, we introduce a Kalman predictor, and show an approach to reduce the computational complexity. We discuss the use of perceptual weighting within the system, and bit error resynchronization for the Arithmetic Coding (AC) data stream. We also mention briefly some concerns related to possible applications of the scheme. We discuss the use of a variable bit rate ADPCM system for speech coding. We present an ADPCM system, using Arithmetic Coding and Kalman Filtering techniques, that can code signals at very low bit rates, where standard fixed bit rate ADPCM systems fail. The proposed system, at an average bit rate of 16 kbps, produces a reconstructed speech signal that by informal listening tests has been judged to be of significantly higher quality than the LD-CELP 16 kbps speech coding standard. We believe that the output quality is comparable to that of LD-CELP at an average rate of around 12 kbps, and the quality at 8 kbps is very promising. Other advantages of the scheme are a reduction in complexity over the LD-CELP standard, and an increase in design flexibility. 2. ADPCM DESTABILIZATION EFFECTS Fixed rate ADPCM systems such as that shown in block form in Figures 1 and 2, generally consist of both adaptive quantizers and adaptive predictors. For speech coding, this adaptation is used to account for the wide variations in the input signal statistics.