Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1990-12-11
1992-08-04
Peng, John K.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358140, 358141, H04N 712, H04N 701, H04N 704
Patent
active
051363771
ABSTRACT:
A quantizer, with quantization control that is sensitive to input signal characteristics and to output buffer fullness responds to an input signal that is divided into blocks and DCT transformed. The transformed signal is analyzed to develop a brightness correction and to evaluate the texture of the image and the change in texture in the image. Based on these, and in concert with the human visual perception model, perception threshold signals are created for each subband of the transformed signal. Concurrently, scale factors for each subband of the transformed signal are computed, and a measure of variability in the transformed input signal is calculated. A measure of the fullness of the buffer to which the quantizer sends its encoded results is obtained, and that measure is combined with the calculated signal variability to develop a correction signal. The correction signal modifies the perception threshold signals to develop threshold control signals that are applied to the quantizer. The scale factors are also applied to the quantizer, as well as a global target distortion measure.
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Johnston James D.
Knauer Scott C.
Matthews Kim N.
Netravali Arun N.
Petajan Eric D.
AT&T Bell Laboratories
Brendzel Henry T.
Peng John K.
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