Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1989-05-03
1990-08-28
Groody, James J.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358135, H04N 712
Patent
active
049530240
ABSTRACT:
In a predictive encoding circuit the transmission of prediction errors to the predictive decoding circuit is selectively suppressed and prediction errors having a predetermined value are applied to the prediction circuit in both the encoding circuit and in the decoding circuit, instead of the non-transmitted prediction errors. In order to determine which prediction errors are not transmitted, a masking function value is determined for an actual pixel in the encoding circuit. This is a linear combination of weighted difference between two pixel values of a predetermined cluster of pixels located in the vicinity of the actual pixel. The actual prediction error is not transmitted only if, for example this masking function value is within a certain range and the previous prediction error has been transmitted. In the decoding circuit the masking function values are determined, starting from the regained local pixel values.
REFERENCES:
patent: 3824590 (1974-07-01), Limb
patent: 4179710 (1979-12-01), Ishiguro et al.
patent: 4232338 (1980-11-01), Netravali et al.
"Digital Image Processing"; Pratt; A Wiley Interscience Publication, John Wiley and Sons; 1978; pp. 637-648.
"Adaptive Quantization of Picture Signals Using Spatial Masking"; Netravali et al., IEEE Proceedings, vol. 65 #4; 4-'77; pp. 536-548.
Groody James J.
Kostak Victor R.
Lobato Emmanuel J.
Marion Michael E.
U.S. Philips Corp.
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