Apparatus and method of attenuating distortion introduced by a predictive coding image compressor
US4785356A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 24, 1987 |
| Grant date | Nov 15, 1988 |
| Priority date | — |
| Expiry date | Apr 24, 2007 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N19/593
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
The present invention relates to a predictive coding method and related apparatus which (a) computes a value D representing the difference between an original graylevel value for a current pixel and a predicted value for the current pixel; (b) associates each successive range of D values to a respective quantization level, each quantization level QN having a respective QN value representing the range corresponding thereto; (c) sets a respective QERR value to D for the current pixel, when the QN value is zero; (d) re-maps m QERR values to n (n.ltoreq.m) MERR values; (e) assigns to the value MERR=O those QERR values in which .vertline.QERR.vertline..ltoreq.(+Q1 VALUE)/2 sums the MERR values for successive pixels in a QN=QO region; and (f) adjusts the QN value from the value of QO by the value of Q1 for a pixel at which the summed value reaches a predefined threshold. QN values, adjusted as appropriate, are subjected to entropy coding compression and decompression. In the decompression process, pixel values are reconstructed. According to the invention, the reconstructed values are subjected to a vertical filter in which a pixel having a reconstructed value I.sub.0 is filtered to have…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.