Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1977-08-23
1980-02-19
Griffin, Robert L.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358260, H04N 712
Patent
active
041897480
ABSTRACT:
A reduction in bandwidth of two-dimensional video data is obtained by the two-dimensional transformation of the video data by means of one of a class of fast transformations followed by the elimination of certain non-significant transform coefficients prior to the transmission of the transform data. The lower-order transform coefficients or "zonal coefficients" which are usually significant in size, are always transmitted. Prior to transmission, parity bits are added to the zonal coefficients to allow error detection. An adaptive filter eliminates from the higher-order transform coefficients, those non-significant transform coefficients of magnitude less than a threshold level, which level is adjusted in response to the amount of data in the buffer memory awaiting transmission so as to transmit the most significant transform coefficients from a succession of two-dimensional data vectors. At the receiving end of the communication link the array of transform coefficients is reconstituted from the received data. The non-zonal coefficients, eliminated prior to transmission, are replaced by zeros in the reconstituted array. Transmission errors occurring in the zonal coefficients, are detected by parity checks and the erroneous zonal coefficients are replaced by the like transform coefficients from the previously received zonal coefficients corresponding to the prior scan of the same portion of the two-dimensional video data. An approximation to the original video data is obtained by the application of the inverse two-dimensional transformation to the reconstituted array of transform coefficients.
REFERENCES:
patent: 3422227 (1969-01-01), Brown
patent: 3580999 (1971-05-01), Mounts
patent: 3585586 (1971-06-01), Harmon et al.
patent: 3679821 (1970-04-01), Schroeder
patent: 3984626 (1976-10-01), Mounts et al.
patent: 4038539 (1977-07-01), Van Cleave
Picture Bandwidth Compression--Application of Fourier-Hadamard Transformation to Bandwidth Compression--Pratt, Andrews-Gordon & Breach Science Pubs., 1972, pp. 515-554.
Tschen, Motsch--Television Image Coding by Means of Hadamard and Haar Orthogonal Transformations--Acta Electronica 19, 3/1976, pp. 255-270.
Griffin Robert L.
Northrop Corporation
Orsino Jr. Joseph A.
Sokolski Edward A.
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