Linear inter-frame dependencies for very low bit-rate speech coding ?
We have studied experimentally the operational rate-distortion performance for very low bit-rate speech coding using linear inter-frame dependencies. We propose an algorithm that efficiently combines quantization and linear interpolation procedures. With a maximum delay of 200 ms, for the spectral envelope information and using line spectrum pair (LSP) parameters as input space the proposed algorithm performs best at rates of between 200 and 300 b/s. For comparison's sake several other procedures such as the multi-frame encoder (Kemp D., Collura J., Tremain T., Multi-Frame Coding of LPC Parameters at 600800 bps. In: IEEE ICASSP-91, 1991, pp. 609612) and matrix quantizer (Tsao C., Gray R., Matrix quantizer design for LPC speech using the generalized Lloyd algorithm. IEEE Transactions on Acoustics, Speech, and Signal Processing ASSP-33, 1985, 537545) are simulated. Furthermore, a mono-dimensional version of the proposed procedure is shown experimentally to provide the best operational rate-distortion trade-off when coding a parametric representation (pitch, gain and voicing information) of the excitation signal.
inter-frame dependencies speech coding quantization interpolation