Coding apparatus

Details Coding apparatus Coding apparatus

1990-12-21

1993-04-20

Chin, Tommy P.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358135, 358432, H04N 712

Patent

active

052047431

ABSTRACT:
A coding apparatus, in which each block having a plurality of picture elements with digital image signals is divided into a plurality of sub-blocks, and an appropriate quantization step or weighting factor is decided on the basis of the absolute value sum of difference of image signal level between adjacent picture elements in the sub-block, so that a digital image signal is reduced. Moreover, a coding apparatus, in which each block having a plurality of picture elements with digital image signals is divided into a plurality of sub-blocks, and an appropriate quantization step or weighting factor is decided on the basis of the maximum and minimum values of the image signals of the picture elements in the sub-block, so that a digital image signal is reduced. Accordingly, in the coding apparatus as above, the state of the image is recognized for every block, whereby a block whose degradation of image quality is hard to notice at the decoder side is quantized or subjected to weighting with low rate, that is, with large reduction rate, whereas a block whose degradation of image quality is conspicuous at the decoder side is quantized or subjected to weighting with high rate, i.e., with small reduction rate. As a result, the image quality of the background having little change in the signal is kept good.

REFERENCES:
patent: 4734767 (1988-03-01), Kaneko et al.
patent: 4890161 (1989-12-01), Kondo
patent: 5073821 (1991-12-01), Juri
S. M. C. Borgers et al., "An expt. Digital VCR with 40 Drum", Single Actuator & DCT-based Bit-Rate Reduction, vol. 34, No. 3.

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