Medium band speech coding using a dictionary of waveforms

The paper presents a new approach to the problem of speech coding in the range of 4 to 8 kbits/sec along with experimental tests performed on a MAP 200 array processor. The basic idea consists of using a dictionary of K indexed waveforms of fixed duration T (where T lies between 1 and 4 ms). The input signal is broken down into blocks of duration T. For each segment the Dictionary is searched for that prototype waveform which is, with respect to some distance measure, the closest to the input block. The digital representation of the signal is thereafter the index of the prototype. The paper addresses the problem of the judicious choice of distance measures and the design of a good dictionary. Experimental results are provided for dictionary coding of the signal using a distance measure combining time and frequency domain features. Experimental results are further presented for the coding of the LPC residual.