Experiments with a regular pulse CELP coder for the pan European half rate channel

Abstract

Various experiments that have been carried out for the realization of a combined speech and channel coder to be submitted as a candidate for the standardization of the pan-European half-rate channel are described. The speech coder is based on the code-excited linear prediction (CELP) technique and involves binary regular pulse excitation (RPCELP). Fast codebook search procedures are described, and a fast algorithm for closed-loop long-term prediction is introduced. Fractional pitch analysis can be performed with a small computational load. The channel coder uses a convolutional code with an error detection code for the most sensitive bits. The global solution was designed to reduce the effects of transmission errors. The proposed half-rate codec is real-time implemented in fixed point with a very low complexity. Results indicate that speech quality remains close to that of the full-rate codec for all transmission conditions. >