This paper describes a 8. 4 kBit/s RPE-coder which is modified to form a variable bit rate coder with an average bit rate of 5 kBit/s. To realize such variable bit rates, the coding scheme must depend on the type of the speech segment to be encoded. Reduction has been achieved for segments that are spectrally stationary (repetition of an LPC parameter set), non-periodic (omission of an LTP parameter set), unvoiced (modeling of the residual as a noise source) or contain background noise (simple coding of station- ary background noise). To classify these states we used distance measures, perceptive thresholds and a robust adaptive Voiced-Unvoiced-Silence (VUS) detector.
Bibliographic reference. Meyer, Peter / Peters, W. / Paulus, J. (1991): "Variable rate speech coding using perceptive thresholds and adaptive VUS detection", In EUROSPEECH-1991, 809-812.