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A method for LPC analysis in a transformed domain (LPCTD) has been developed theoretically and studied experimentally in the Walsh-Hadamard domain (LPCWHD) for low-bit- rate coding of speech signals . Speech signals in the Walsh-Hadamard domain have been modelled by their largest variance coefficients and a few prediction coefficients which represent the remaining coefficients. Determination of the prediction coefficients has been based on the correlation between the spectral coefficients. Intelligible speech at bit-rates of 8 kb/s and 4 kb/s was achieved when 16 and 64 point Walsh-Hadamard transforms were used, respectively. At the latter bit-rate the quality was significantly improved when unvoiced sounds were coded seperately by their largest variance coefficients. The main advantage of LPCWHD system is its simplicity which can lead to a far less complex implementation than that of vocoder systems.
Acoustics, Speech, and Signal Processing, IEEE International Conference on ICASSP '78. (Volume:3 )
Date of Conference: Apr 1978