Speech coding with an analysis-by-synthesis sinusoidal model
C.O. Etemoglu, V. Cuperman, A. Gersho · 2002
We introduce a general and powerful approach to sinusoidal modeling of speech wherein a closed-loop analysis-by-synthesis (AbS) technique sequentially extracts the parameters for each sinusoidal component. Low bit-rate speech coding is achieved by efficiently constraining the allowed frequencies of sinusoidal components into sets of frequency intervals or bins. In conjunction with the closed-loop analysis, the constrained frequency regions allow us to efficiently vector quantize the frequency information in each frame. In voiced frames, two sets of frequency vectors are generated: one for harmonically related components and the other for non-harmonically related components of the voiced segment. In transition frames, a vector of nonuniformly spaced frequencies is selected from a frequency codebook using frequency bin vector quantization (FBVQ) to represent the frequency domain information. The effectiveness of the coding scheme is enhanced by exploiting the critical band concept of auditory perception in defining the frequency bins. In transition segments, the sinusoidal phases are modeled and coded. Subjective tests with a partially quantized model indicate that, for a target rate of 4 kbps, the coder quality exceeds that of the G.729 standard at 8 kbps.