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

Abstract

The paper descnbes the various experiments that have been carried out at Matra Communication 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. The speech coder is based on the CELP technique and involves binary Regular Pulse excitation (RPCELP). Fast codebook search procedures are described and a new fast algorithm for closed-loop long term prediction is introduced. Then 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. First results indicate that speech quality remains close to that of the full rate codec for all transmission conditions.