Abstract: An efficient, fast-decoding, order-preserving, easily implementable, length-based (L-based) arithmetic coding method, apparatus, and manufacture for an m-ary alphabet {1, . . . , i, . . . , m} is provided. A coding method in accordance with the invention combines recursive division of intervals on a number line into sub-intervals whose lengths are proportional to symbol probability and which are ordered in lexical order with the constraint that probabilities be estimated as negative powers of two (1/2, 1/4, 1/8, etc.). As a consequence, the advantageous preservation of lexical order and computational efficiency are both realized. Also, a coding system in accordance with the invention is simple to implement, and high speed operation is achieved, because shifts take the place of multiplications. A coding apparatus in accordance with the invention preferably includes either a single decoding table to achieve fast decoding, or two decoding tables to achieve fast decoding as well as order preservation.

Abstract: A method for data compression of records in storage that offers the decoding speed of Variable-to-Fixed codes without loss of sort order characteristics when stored in coded form. The methods include special treatment of the first ordered symbols in both source and decoder alphabets and do not depend on the use of prefix or arithmetic codes for their efficacy. The method saves database storage space by compressing actual records without loss of record sort order characteristics. The lexical ordering or "strong alphabetical" property of the encoding technique are left undisturbed by EOR codes and code-string terminations for byte-padding purposes because both EOR and code-string termination is accomplished with a zero-valued code word. This maintains record order through a proper magnitude relationship between the corresponding encoded records even if one record compresses to a different length than another.

Abstract: A tape drive system includes a compaction scheme whereby the data to be stored on the media is encoded and formatted to take less space along the tape length. The data to be written to tape is placed into equal byte lengths or sets. The sets of data are directed to a plurality of encoders in turn and compacted through an Arithmetic Binary Coding program having two statistic tables per encoder to allow format compatibility with a higher throughput compaction scheme. The compacted sets are sequenced and formed into packets. Then the packets are autoblocked to delineate the packets while providing a single Inter Block Gap per autoblock length and written on the tape. On read, the data is retrieved from the tape and deblocked to separate the packets. Each packet is separated into compacted sets of data. The compacted sets are directed to a plurality of decoders in turn and decompacted. The decompacted sets are to resequenced to place the data into the same state as originally transmitted.

Abstract: Apparatus and method for compressing and de-compressing binary decision data by arithmetic coding and decoding wherein the estimated probability Qe of the less probable of the two decision events, or outcomes, adapts as decisions are successively encoded. To facilitate coding computations, an augend value A for the current number line interval is held to approximate one by renormalizing A whenever it becomes less than a prescribed minimum AMIN. When A is renormalized, the value of Qe is up-dated. The renormalization of A and up-dating of Qe are preferably based on a single-bit test. Also, each Qe value is preferably specified as a 12-bit value having the least significant bit set to 1 and having no more than four other bits set to 1. The number of Qe values in the 1/4 to 1/2 probability range is enhanced to improve coding efficiency.

Abstract: This invention relates to method and apparatus for compressing multilevel signals. The compression 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.

Abstract: A class of ternary square wave signals is detectable by peak polarity detection alone without need for amplitude discrimination. The ternary codes are used to increase data density recording at the same clock rate as binary codes. This is satisfied by selective direction-constrained run length limited (RLL) signals. The direction constraint is that the half-step transitions can only occur in pairs of the same polarity. Alternate half-step pairs of opposite polarity are forbidden. This avoids the need for amplitude discrimination. The RLL (d,k) constraint includes "d" number of clock times when a transition is forbidden and "k>d" clock times within which consecutive transitions must occur. The latter determines a minimum frequency for clocking purposes. This eases peak shift detection.

Abstract: A two-stage single pass adaptive modeling method and means for a finite alphabet first order MARKOV symbol source where the model is used to control an encoder on a per symbol basis thereby enabling efficient compression within a fixed preselected implementation complexity.

Abstract: A method and apparatus for recursively generating an arithmetically compressed binary number stream responsive to the binary string from conditional sources. Throughput is increased by reducing the number of operations required to encode each binary symbol so that only a single shift of k bits is required upon receipt of each least-probable symbol or an "add time", followed by a decision and a one-bit shift in response to each most-probable symbol encoding. The concurrent augmentation of the compressed stream and an internal variable involves only the function of a probability interval estimate of the most-probable symbol, and not upon the past encoding state of either variable (2.sup.-k, 49, 63, C, T). Each binary symbol may be recovered by subtracting 2.sup.-k from the q-most-significant bits of the compressed stream and testing the leading bit of the difference.

Abstract: Carry-over control in strings resulting from the high to low order combining of two binary number strings is obtained through the insertion of a control character within the resultant string after detecting a run of consecutive 1's. Upon subsequent accessing and decomposition of the resultant string, the control character causes string decomposition to operate for a number of cycles in a carry correction mode. If the control character indicates that a carry has rippled through the n lesser significant positions of the resultant string, then upon decomposition, those "n" consecutive 1's are changed to 0's, and a 1 is added to the least significant position in the string preceding the control character. If the control character indicates no carry occurrence, then it is merely deleted from the string. The control of carries in this manner permits the generation of arithmetic string compression code sequences in an instantaneous FIFO pattern with only a modest reduction of compression efficiency.

Abstract: An apparatus for ensuring continuous flow through a pipeline processor as it relates to the serial decoding of FIFO Rissanen/Langdon arithmetic string code of binary sources. The pipeline decoder includes a processor (11, 23) and a finite state machine (21, FSM) in interactive signal relation. The processor generates output binary source signals (18), status signals (WASMPS, 31) and K component/K candidate next integer-valued control parameters (L0, k0; L1, k1; 25). These signals and parameters are generated in response to the concurrent application of one bit from successive arithmetic code bits, a K component present integer-value control parameter (52) and K component vector representation (T, TA) of the present internal state (51) of the associated finite state machine (FSM). The FSM makes a K-way selection from K candidate next internal states and K candidate next control parameters. This selection uses no more than K.sup.2 +K computations.

Abstract: A method and means of arithmetic coding of conditional binary sources permitting instantaneous decoding and minimizing the number of encoding operations per iteration. A single shift and subtract operation for each encoding cycle can be achieved if an integer valued parameter representative of a probability interval embracing each source symbol relative frequency is used for string encoding and control. If the symbol being encoded is the most probable, then nothing is added to the arithmetic code string. However, an internal variable is updated by replacing it with an augend amount. If the updated internal variable has a leading zero, then both it and the code string are shifted left by one position. If the symbol being encoded is the least probable, then a computed augend is added to the code string and the code string is shifted by an amount equal to the integer valued parameter.

Abstract: A method and means for creating the display illusion of "roughness" or "texture" in color patterns suitable for an raster scanned display surface by assigning different color values to pels (picture elements) in adjacent positions and then replicating the patterns automatically using the recurrent and sequential accessing of a concordance table. The real color of each pel of a textured pattern is a joint function of a color number stored in a refresh buffer driving the display surface for any given display matrix array pel position and the value of a predetermined subset of address bits which describe that pel position. The use of preselected pel position address bits for regulating texture is shown as applied to video lookup tables and refresh buffers as a singlelevel control and additionally to two or more video lookup tables for achieving a pattern hierarchy.

Abstract: There is disclosed a method and means for increasing the positional accuracy of operator controlled cursors engaged in the digitized encoding of graphic information such as line drawings. The method steps comprise those of digitizing the instantaneous contact position between the cursor and the data entry surface as reference coordinates; detecting any segment of a colored object upon the surface within a predetermined area about the cursor; ascertaining the location within the area of the centroid or the like of the detected segment; and digitizing said ascertained location as a displacement from the reference coordinates. Apparatus for practicing the method comprises an independently actuable cursor formed from a position encoder and an image scanner, the scanner generating a Boolean coded array of points counterpart to a preselected surface area.

Abstract: An improved video display system is provided in which two color images are combinable in a dynamic and self-determining fashion to provide improved contrast, comprehension and display versatility. Two separate video signals that are to be used in generating a single display are converted into sequences of digitally encoded picture elements (pixels). Control signals are generated that are dependent upon the data content of the elements in at least one of the sequences, and these signals are used to govern the mode of combination of the two video signals for individual pixel sets. For example a first video signal of digital character and having varying pixel intensity may be transformed into color values for a first pseudocolor display. A second video signal, derived from an analog source, is digitized and is also transformed into pseudocolor, concurrent with the dynamic generation in real time of the data dependent control signals.

Abstract: Method and means are described for the tracking of digit significance upon operands arithmetically combined in a series of binary operations such as addition, subtraction, or shifting in a decimal computer. The digits are decimally encoded in a format having enough excess capacity such that nonsignificant digits are unique. As part of the arithmetic combining of the operand, pairs of digits of like order but possibly mismatched as to significance and by observing a predetermined rounding rule may also cause a carry value to be propagated to a digit position of higher order. In subtraction by complement addition, an additional carry is propagated to a higher order position conditioned upon there being either a local overflow, a nonsignificant subtrahend, or a nonsignificant minuend and a subtrahend less than an amount specified by a rounding rule. Between the two operands, this results in the rounding of the more precise operand to the least significant digit position of the less precise operand.