EP0245621A2
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EP
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Compression of multilevel signals
Assignee: International Business Machines Corp
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Filing: 1987-03-20
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Granted: —
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Expires: 2007-03-20
Abstract
Abstract A method of and apparatus for compressing multilevel signals is based upon prediction errors and probability distributions. Compression is improved by conditioning the probability distributions using context of previous events. Storage required for storing the probability distributions is reduced by partitioning the prediction errors into predetermined ranges which become the coding events and contexts. Compression is made efficient with a partition which is a function of the sign and the number of significant bits in the prediction errors. Counterpart decoding is also disclaosed.
Inventors
- 👤 Glen George Langdon, Jr.
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-31 11:20
CPC Classifications
H; H04; H04N; H04N19/00; H04N19/50; H04N19/593; H03; H03M; H03M7/00; H03M7/30; H03M7/40; H03M7/4006; H04N19/90
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
115 words
A method of compressing a plurality of multilevel signals, comprising the steps of: (a) predicting a value of one of the plurality of multilevel signals; (b) detecting an actual value of the one signal; (c) calculating a prediction error responsive to the difference between the actual value and the predicted value; (d) assigning the prediction error to one of a plurality of predetermined error ranges, each range being a function of the sign and the number of significant digits of the prediction error value; (e) assigning a probability distribution to each such error range; and (f) encoding the prediction error using the probability of a corresponding error range to which the prediction error is assigned.
Claim 2
Independent Claim
115 words
A method of compressing a plurality of multilevel signals, comprising the steps of: (a) predicting a value of one of the plurality of multilevel signals; (b) detecting an actual value of the one signal; (c) calculating a prediction error responsive to the difference between the actual value and the predicted value; (d) assigning the prediction error to one of a plurality of predetermined error ranges, each range being a function of the sign and the number of significant digits of the prediction error value; (e) assigning a probability distribution to each such error range; and (f) encoding the prediction error using the probability of a corresponding error range to which the prediction error is assigned.
Claim 3
Dependent Claim
24 words
A method as claimed in claim 1, including the step of encoding the absolute value of the prediction value with its assigned error range.
Claim 4
Dependent Claim
59 words
A method as claimed in claim 1 including the steps of assigning to an error range designated as corresponding to a specific error value, prediction errors having a corresponding number of significant digits up to a predetermined value, and assigning to a separate error range all error values having a number of significant digits greater than the predetermined value.
Claim 5
Dependent Claim
65 words
A method as claimed in claim 1, wherein the encoding of the prediction error includes (i) converting the prediction error into an exponent part and a mantissa part; (ii) encoding the exponent part statistically, using a subset of prediction errors calculated from others of the plurality of multilevel signals as context; and (iii) combining the encoded exponent part with an encoding of the mantissa part.
Claim 6
Dependent Claim
46 words
A method as claimed in claim 4, wherein the conversion of the prediction error into an exponent part and a mantissa part is performed using a base of two, but is omitted if the prediction error is zero, in which case it is explicitly so encoded.
Claim 7
Dependent Claim
123 words
Apparatus for compressing a plurality of multilevel signals, comprising: (a) means for predicting a value of one of the plurality of multilevel signals; (b) means for detecting an actual value of the one signal; (c) means for calculating a prediction error responsive to the difference between the actual value and the predicted value; (d) means for assigning the prediction error to one of a plurality of predetermined error ranges, each range being a function of the sign and the number of significant digits of the prediction error value; (e) means for assigning a probability distribution to each such error range; and (f) means for encoding the prediction error using the probability of a corresponding error range to which the prediction error is assigned.
Claim 8
Dependent Claim
123 words
Apparatus for compressing a plurality of multilevel signals, comprising: (a) means for predicting a value of one of the plurality of multilevel signals; (b) means for detecting an actual value of the one signal; (c) means for calculating a prediction error responsive to the difference between the actual value and the predicted value; (d) means for assigning the prediction error to one of a plurality of predetermined error ranges, each range being a function of the sign and the number of significant digits of the prediction error value; (e) means for assigning a probability distribution to each such error range; and (f) means for encoding the prediction error using the probability of a corresponding error range to which the prediction error is assigned.
Claim 9
Dependent Claim
145 words
Apparatus for compressing a plurality of multilevel signals, comprising: (a) a predictor for predicting a value of one of the plurality of multilevel signals; (b) a detector for detecting the actual value of the one signal; (c) a comparator responsive to the outputs of the predictor and the detector for determining a prediction error ; (d) means for determining whether the prediction error is zero; (e) means responsive to a prediction error of zero for encoding a zero; and (f) means responsive to a prediction error other than zero for: (i) generating an indication of the sign of the prediction error; (ii) means for generating an indication of the digit position of the most significant non-zero digit of the absolute value of the prediction error; and (iii) means for generating an indication of the absolute value of the digits following the most significant non-zero digit.
Claim 10
Dependent Claim
145 words
Apparatus for compressing a plurality of multilevel signals, comprising: (a) a predictor for predicting a value of one of the plurality of multilevel signals; (b) a detector for detecting the actual value of the one signal; (c) a comparator responsive to the outputs of the predictor and the detector for determining a prediction error ; (d) means for determining whether the prediction error is zero; (e) means responsive to a prediction error of zero for encoding a zero; and (f) means responsive to a prediction error other than zero for: (i) generating an indication of the sign of the prediction error; (ii) means for generating an indication of the digit position of the most significant non-zero digit of the absolute value of the prediction error; and (iii) means for generating an indication of the absolute value of the digits following the most significant non-zero digit.
Claim 11
Dependent Claim
13 words
Apparatus as claimed in claim 6 or claim 7, further including a decoder.
References Cited (Backward Citations)
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