On improving the performance of a two-digit encoding scheme using a modified predictor

This paper presents an efficient two-digit algorithm for coding speech at low bit rates. This algorithm was suggested based on the constant factor algorithm (CFA) used in adaptive quantization. This has lend to an improvement in SNR and larger dynamic range at the expense of a small increase in the required channel bandwidth. A further improvement to the two-digit system is demonstrated by using an optimized second-order prediction which achieves a gain of 3 to 4 dB in SNR over the original first-order system. Moreover a two-digit speech coder with an incremental step size adaptation algorithm is proposed to benefit from the advantages of simple and efficient speech encoders using incremental step size adaptation such as the Song Voice Incremental Algorithm (SVIA).