Picturetel Corporation

Gary J Sullivan

Gregory W Wornell

Henrique S Malvar

A method and apparatus for encoding a sampled signal using a nonscalar vector quantizer. A lapping window operator is applied to blocks of signal samples of length greater than N to produce length-N transform vectors which are then encoded by a nonscalar vector quantizer. The method and apparatus may use or have a window operator that is identical to that of the modulated lapped transform, that is a 2N.times.N matrix operator, that is identical to that of the modulated lapped transform with asymmetrical, orthogonal butterflies, or that has butterfly transmittances given by h�n!=sin�(2n+1).pi./4N!. The method and apparatus may use or have a vector quantizer is an unconstrained mean-square optimized vector quantizer having codewords of length N. The method and apparatus may use or have a vector reconstructor being an inverse of the nonscalar vector quantizer to reconstruct length-N vectors coupled through a transmission channel to received the length-N vectors from the vector quantizer, and a block decoder connected to receive as input the reconstructed length-N vectors from the vector reconstructor and to apply a reconstructor window operator to produce vectors that may be superimposed to generate a reconstruction of the sampled signal. The reconstructor window operator may be the inverse of the lapping window operator.

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Arlington, MA, United States of America

Gary J Sullivan