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公开(公告)号：CA1291821C
公开(公告)日：1991-11-05
申请号：CA544052
申请日：1987-08-07
Applicant: IBM
Inventor： LANGDON GLEN G JR , MITCHELL JOAN L , PENNEBAKER WILLIAM B , RISSANEN JORMA J
Abstract: YO986-091 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. A decision coding parameter of preferably six bits indicates the sense of the more probable symbol (MPS) in one bit and identifies a corresponding Qe value with the remaining five bits. In addition to probability adaptation, the present invention discloses an allocation of bits in a code stream register in which preferably two spacer bits are inserted between a next byte portion (which contains a byte of data en route to a buffer) and a fractional portion which may be involved in further computation. With the two spacer bits, any code greater than or equal to Hex 'CO' which fol YO986-091 lows a Hex 'FF' byte is illegal for data and therefore provides for an escape from the code stream. The two spacer bits also reduce the number of stuff bits inserted to account for carry or borrow propagation. Encoding and decoding can be performed interchangeably by hardware or software which feature differing coding conventions.
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公开(公告)号：CA1236563A
公开(公告)日：1988-05-10
申请号：CA472899
申请日：1985-01-25
Applicant: IBM
Inventor： MITCHELL JOAN L , PENNEBAKER WILLIAM B
Abstract: A method, embodying the present invention, for suppressing the perception of flicker in interlaced video images, includes the steps of: testing, each pixel in an image, for an intensity value below a first predetermined threshold; modifying, for each tested pixel, an intensity value representation for each nearest neighbor pixel along a first axis of said interlaced image having an intensity value exceeding a second predetermined threshold, if the intensity value of the tested pixel is below the first predetermined threshold; displaying, on a video display device, an interlaced image generated by the steps of testing and modifying, having a suppressed perception of flicker.
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公开(公告)号：CA2062155C
公开(公告)日：1998-04-28
申请号：CA2062155
申请日：1992-03-02
Applicant: IBM
Inventor： PENNEBAKER WILLIAM B
Abstract: A system and method for masking adaptive quantization during compressed image data transmission by defining a scaling factor for the quantization tables of the multiple image components, wherein the scaling factor signals changes in quantization for successive blocks of the image data. The scaling factor is transmitted as a further component together with the image components to thereby signal adaptive quantization of the image data.
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公开(公告)号：DE69220541T2
公开(公告)日：1998-01-15
申请号：DE69220541
申请日：1992-04-06
Applicant: IBM
Inventor： PENNEBAKER WILLIAM B
Abstract: A system and method for masking adaptive quantization during compressed image data transmission by defining a scaling factor for the quantization tables of the multiple image components, wherein the scaling factor signals changes in quantization for successive blocks of the image data. The scaling factor is transmitted as a further component together with the image components to thereby signal adaptive quantization of the image data.
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公开(公告)号：DE3751371T2
公开(公告)日：1996-02-15
申请号：DE3751371
申请日：1987-08-18
Applicant: IBM
Inventor： MITCHELL JOAN L , PENNEBAKER WILLIAM B
IPC: H03M7/40
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Patent Agency Ranking
公开(公告)号：DE3751371D1
公开(公告)日：1995-08-03
申请号：DE3751371
申请日：1987-08-18
Applicant: IBM
Inventor： MITCHELL JOAN L , PENNEBAKER WILLIAM B
IPC: H03M7/40
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公开(公告)号：CA2008370C
公开(公告)日：1995-02-07
申请号：CA2008370
申请日：1990-01-23
Applicant: IBM
Inventor： TOYOKAWA KAZUHARA , PENNEBAKER WILLIAM B , ANDERSON KAREN L , MITCHELL JOAN L
Abstract: : A system is described for reformatting halftone data for compression, wherein an original bilevel image is reformatted to produce another bilevel image that allows vertical correlations to be recognized by the compression technique, thus improving compressibility dramatically, with particular suitability for facsimile transmissions. In reformatting it is assumed that a selected halftone frequency H will satisfactorily describe an entire document, and each of successive sets of N consecutive lines are concatenated to form respective single lines. The thus reformatted lines have a clearer halftone periodicity offering greater correlation and permit more efficient coding by well-known standard bilevel compression algorithms (e.g., CCITT G3 (MR) or G4 (MMR)). For an image with unknown pattern frequency, a technique for readily estimating the frequency for use in reformatting the image is described. Y0989-001
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公开(公告)号：DE3886804T2
公开(公告)日：1994-06-23
申请号：DE3886804
申请日：1988-04-06
Applicant: IBM
Inventor： GONZALES CESAR A , PENNEBAKER WILLIAM B
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公开(公告)号：DE3789857D1
公开(公告)日：1994-06-23
申请号：DE3789857
申请日：1987-12-01
Applicant: IBM
Inventor： GONZALES CESAR A , PENNEBAKER WILLIAM B , MITCHELL JOAN LAVERNE
IPC: H03M7/38 , G06T9/00 , H04N7/32 , H04N19/593 , H04N7/137
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公开(公告)号：CA1301308C
公开(公告)日：1992-05-19
申请号：CA485178
申请日：1985-06-25
Applicant: IBM
Inventor： PENNEBAKER WILLIAM B
Abstract: THRESHOLDING TECHNIQUE FOR GRAPHICS IMAGES USING HISTOGRAM ANALYSIS A system is described for thresholding graphics images to reduce the information content for transmission and reproduction and which uses a particular image data thresholding technique that may be used to obtain display images with a number of intensity levels. Firstly, an histogram of the image to be encoded is generated and analyzed to determine essential parameters. In particular, the background color of the image is determined by summing the histogram elements to find the median of the distribution, that is, the point at which the half sum of total pixels is reached. The extrema of the histogram are calculated and the skew is determined from the position of the median with respect thereto. If the difference between the median and the black extreme is less than half the difference between the median and the white Y0984-057 extreme then the background of the image is deemed to be black, otherwise, the image will be defined as having a white background. After the background color is determined, the width of the background region, that is, the difference between the median and the foreground color extreme, is used to define the edge between the background and foreground regions, which edge occurs at one-half the background width from the median in the direction of the background color extreme. A sequence of threshold levels may then be determined using this edge as a base, by setting them at points disposed at fractionally different distances between the edge and the background color extreme. Preferably the levels are set at points 1/8, 1/4 and 1/2 the defined distance or at 3/16, 3/8 and 3/4. The selected points will respectively define the threshold levels such as between white/gray-white, graywhite/gray-black, and gray-black/black. Thus, the resulting image may then, after encosing and transmission, be decoded and displayed on a suitable teleconferencing system or fascimile machine with four intensity levels. Y0984-057
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