US4748577A
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Logarithmic data compression
Assignee: General Dynamics Mission Systems Inc
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Filing: 1982-02-02
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Granted: 1988-05-31
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Expires: 2002-02-02
Abstract
Abstract Improved logarithmic data compression is achieved by means of a method of finding a more efficient base and a more efficient memory structure. Data compression from a P-bit input word to a Q-bit output word is performed using an optimal base which produces a number of rounded logarithm values equal to 2 Q when applied to all of the possible input values. These logarithm values are coded using the available output values to produce a logarithm look-up table. The look-up table is implemented using a multi-stage memory structure which reduces the number of memory devices required for a given table.
Inventors
- 👤 Jeffrey D. Marchant
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 22:50
CPC Classifications
G; G06; G06F; G06F1/00; G06F1/02; G06F1/03; G06F1/035; G06F1/0356; G06F2101/00; G06F2101/10
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
97 words
A multi-stage logarithmic data compression apparatus responsive to input word for producing an output word comprising: means for separating said input word into a plurality of portions; and a plurality of memory stages, a first of said stages being responsive to a first portion of said input word to produce a logarithm according to an optimal base, second and subsequent of said stages being responsive to an output of a previous stage and a portion of said input word to produce a logarithm according to an optimal base, a last of said stages producing said output word.
Claim 2
Dependent Claim
97 words
A multi-stage logarithmic data compression apparatus responsive to input word for producing an output word comprising: means for separating said input word into a plurality of portions; and a plurality of memory stages, a first of said stages being responsive to a first portion of said input word to produce a logarithm according to an optimal base, second and subsequent of said stages being responsive to an output of a previous stage and a portion of said input word to produce a logarithm according to an optimal base, a last of said stages producing said output word.
Claim 3
Dependent Claim
186 words
A logarithmic data compression apparatus comprising: means for receiving an input data word and for separating it into at least two portions: a first look-up stage coupled to said receiving means, said first look-up stage receiving a least significant portion of said input data word as an address and producing an output indicative of, but not necessarily equal to, a logarithm of said least significant portion to an optimal base, said optimal base being chosen to fully utilize a number of available output values; and at least one subsequent look-up stage, each coupled to a previous look-up stage and to said means for receiving, each said at least one subsequent stage receiving an output of a previous stage and a portion of said input word as an address and producing an output indicative of, but not necessarily equal to, a logarithm of said address to an optimal base, said optimal base being chosen to fully utilize a number of available output values, a final of said subsequent look-up stages producing an output word indicative of, but not necessarily equal to, a logarithm of said input word.
Claim 4
Dependent Claim
186 words
A logarithmic data compression apparatus comprising: means for receiving an input data word and for separating it into at least two portions: a first look-up stage coupled to said receiving means, said first look-up stage receiving a least significant portion of said input data word as an address and producing an output indicative of, but not necessarily equal to, a logarithm of said least significant portion to an optimal base, said optimal base being chosen to fully utilize a number of available output values; and at least one subsequent look-up stage, each coupled to a previous look-up stage and to said means for receiving, each said at least one subsequent stage receiving an output of a previous stage and a portion of said input word as an address and producing an output indicative of, but not necessarily equal to, a logarithm of said address to an optimal base, said optimal base being chosen to fully utilize a number of available output values, a final of said subsequent look-up stages producing an output word indicative of, but not necessarily equal to, a logarithm of said input word.
Claim 5
Independent Claim
111 words
An apparatus for compressing input words of P bits to output words of Q bits comprising: means for determining a logarithm of said input words according to a base B, said base B being chosen so that a number of rounded output values equal to 2 Q is produced when the logarithm function defined by B is applied to the group of input words comprising all of the integers greater than or equal to zero and less than or equal to 2 P ; and means for associating each said rounded output value with an integer greater than or equal to zero and less than or equal to 2 Q .
Claim 6
Independent Claim
111 words
An apparatus for compressing input words of P bits to output words of Q bits comprising: means for determining a logarithm of said input words according to a base B, said base B being chosen so that a number of rounded output values equal to 2 Q is produced when the logarithm function defined by B is applied to the group of input words comprising all of the integers greater than or equal to zero and less than or equal to 2 P ; and means for associating each said rounded output value with an integer greater than or equal to zero and less than or equal to 2 Q .
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-05-31 | 1991-11-30 | 1992-05-31 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-05-31 | 1995-11-30 | 1996-05-31 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-05-31 | 1999-11-30 | 2000-05-31 | $7700.00 | Window Closed / Lapsed |