Mixed Fourier/Walsh transform scheme for speech coding at 4.0 kbit/s

Abstract
A mixed Fourier/Walsh transform scheme for speech coding is proposed. A set of harmonically structured frequency components is used to represent narrow-band components of speech. The broadband residual is characterised by a small number of sequency components. The frequencies and sequencies of the transform components are determined by sampling the shorttime Fourier and Walsh transforms, respectively. The magnitudes and phases of the Fourier components and the amplitudes of the Walsh components are determined using an iterative algorithm based on the Gauss-Seidel method. A vector quantisation (VQ) scheme is developed to encode the frequency and the sequency components. Results and subjective evaluations are given for speech coding at 4.0 kbit/s

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