Picturetel Corporation

Henrique S Malvar

Gregory W Wornell

Gary J Sullivan

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.

Lapped orthogonal vector quantization

A method and apparatus for processing n-dimensional digitized signals containing at least two adjacent blocks of digitized sample values. The digitized signal is transformed in accordance with a spatial transform operator. The spatial transform operator is characterized by similar size blocks to the blocks in the input signal, but is operative over blocks of the signal which extend beyond the nominal blocks in the signal by a predetermined number of sample values in at least one dimension. The resultant signal may be similarly transformed by another spatial transform operator to obtain an output transform signal. The latter signal is substantially free from blocking artifacts.

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Andover, MA, United States of America

Henrique S Malvar