EP0071680A1
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Data recording or transmission system using run length limited coding
Assignee: IBM United Kingdom Ltd
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Filing: 1981-08-07
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Granted: —
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Expires: 2001-08-07
Abstract
Abstract The invention concerns a data recording or transmission system using run length limited coding. In such a system a length oriented arithmetic decoder (3) constrained to ONE-TO-ONE map in the data string to run length limited string direction and ONTO map in the run length limited to data string direction through an arithmetic encoder (9) preserves the fixed rate of the RLL string and ensures representability. A finite state machine responsive to the arithmetic decoder output provides the trial augends and shift amounts necessary for the magnitude comparison decoding of the data string treated as if it were arithmetically compressed. A finite state machine is also used with the arithmetic encoder for providing trial augends and shift amounts but is responsive to successive RLL symbols as if it were ordinary source strings. The encoder combines the augends with a predetermined retained portion of the generated data string. The ONTO mapping assures that RLL strings do not map Into arithmetic strings which have no RLL string counterparts and which arise out of the nature of recursive arithmetic compression coding while the ONE-TO-ONE mapping assures the existence of an RLL string for each data string. Significantly, the length of the code string is the product of the code string duration times its fixed state. This is independent of encoder/decoder state.
Inventors
- 👤 George Nigel Newcomen Martin
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-01 16:11
CPC Classifications
G; G11; G11B; G11B20/00; G11B20/10; G11B20/14; G11B20/1403; G11B20/1423; G11B20/1426; G06; G06T; G06T9/00; G06T9/005
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
94 words
A data recording or transmission system including apparatus for generating a run length limited (RLL) symbol string u from a data symbol string considered as a compressed code stream F(u)=a(l),a(2), ..., a(i),...a(n), the generating apparatus being characterized by means (Fig. 2) which responds to the data string as if it were a high to low position magnitude order length oriented FIFO arithmetically compressed code stream F(u) and which generates a fixed rate RLL symbol string by the ONE-TO-ONE mapping of each data string F(u) into an arithmetically decoded and expanded symbol string counterpart u.
Claim 2
Dependent Claim
94 words
A data recording or transmission system including apparatus for generating a run length limited (RLL) symbol string u from a data symbol string considered as a compressed code stream F(u)=a(l),a(2), ..., a(i),...a(n), the generating apparatus being characterized by means (Fig. 2) which responds to the data string as if it were a high to low position magnitude order length oriented FIFO arithmetically compressed code stream F(u) and which generates a fixed rate RLL symbol string by the ONE-TO-ONE mapping of each data string F(u) into an arithmetically decoded and expanded symbol string counterpart u.
Claim 3
Dependent Claim
54 words
A data recording or transmission system according to claim 1 further including apparatus for the recovery of the data symbol string from the fixed rate (RLL) symbol string u, the recovery apparatus including means (Fig. 3) for the ONTO mapping of each RLL symbol string into a length oriented FIFO arithmetically compressed code stream.
Claim 4
Dependent Claim
88 words
A system according to claim 1, wherein the generating apparatus for the ONE-TO-ONE string mapping of symbols includes means for performing the following steps per symbol: magnitude comparing a relatively shifted portion of data string F(u) and a trial augend M(s,x,a); selecting as the RLL symbol the counterpart to the largest augend magnitude F(u); subtracting the augend counterpart from F(u); ascertaining the length attribute of the data symbol; and relatively shifting F(u) by 2 E ( u ) where E(u) is the integer value of the length attribute.
Claim 5
Dependent Claim
94 words
A system according to claim 2, wherein the recovery apparatus for the ONTO string mapping of symbols includes means for performing the following steps per symbol: obtaining a trial augend M(s,x,a) as a function of the RLL symbol "a" and a fractional value x of the length attribute; adding a relatively shifted trial augend to a portion of the data string F(u); ascertaining the length attribute of the RL L data symbol; and relatively shifting F(u.a) by 2 E(u.a)-E(u) where E(u) are the integer value of the length recursions on u and u.a, respectively.
Claim 6
Dependent Claim
117 words
A system according to claim 3, wherein the generating apparatus comprises: register means (17,45) for storing a bit string segment; a finite state machine (17) responsive to consecutive RLL symbols for providing a trial augend and a shift amount indicative of the length attribute of a previously encoded data string symbol; a subtractor (49) for ascertaining the magnitude difference between the register contents and the augend; means (21,55,43 and 37) during each encoding cycle for relatively shifting the difference magnitude contents from the subtractor and a data string symbol into the register by the shift amount; and means (control unit 51) for generating an RLL symbol only when the trial augend is greater than the register contents.
Claim 7
Dependent Claim
73 words
A system according to claim 4, wherein the recovery apparatus comprises: a multiple bit register (57); a finite state machine responsive to successive RLL string symbols for generating an augend (29) and a shift amount; an adder for arithmetically combining the register contents with the augend; and means (61,43,63) during each encoding cycle for shifting a predetermined length of the data string adder output into the register as" designated by the shift amount.
Claim 8
Dependent Claim
94 words
A data recording or transmission system including apparatus for maintaining representability of symbol strings in the conversion of data strings into fixed rate run length limited (RLL) symbol strings and vis-a-vis, characterized in that the apparatus comprises means for mapping each data string into an RLL string by serially applying the data strings to a length oriented arithmetic decoder constrained to ensure a ONE-TO-ONE transformation, and means for mapping each RLL string into a data string by serially applying the RLL string to a length oriented arithmetic encoder constrained to ensure an ONTO transformation.
Claim 9
Dependent Claim
94 words
A data recording or transmission system including apparatus for maintaining representability of symbol strings in the conversion of data strings into fixed rate run length limited (RLL) symbol strings and vis-a-vis, characterized in that the apparatus comprises means for mapping each data string into an RLL string by serially applying the data strings to a length oriented arithmetic decoder constrained to ensure a ONE-TO-ONE transformation, and means for mapping each RLL string into a data string by serially applying the RLL string to a length oriented arithmetic encoder constrained to ensure an ONTO transformation.
References Cited (Backward Citations)
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