公开(公告)号：DE3885551T2

公开(公告)日：1994-05-05

申请号：DE3885551

申请日：1988-08-18

Applicant: IBM

Inventor： CHEVION DAN SHMUEL ,  KARNIN EHUD DOV ,  WALACH EUGENIUSZ

IPC: G06T9/00 ,  H04N13/00

公开(公告)号：DE69424229T2

公开(公告)日：2000-11-30

申请号：DE69424229

申请日：1994-06-27

Applicant: IBM

Inventor： HASSNER MARTIN AURELIANO ,  KARNIN EHUD DOV ,  SCHWIEGELSHOHN UWE ,  TAMURA TETSUYA

IPC: G06F5/00 ,  G06T9/00 ,  H03M7/30 ,  H04B1/66 ,  G06F7/02

Abstract: An apparatus and method for executing a sequential data compression algorithm that is especially suitable for use where data compression is required in a device (as distinguished from host) controller. A history buffer 22 comprises an array of i identical horizontal slice units. Each slice unit stores j symbols to define j separate blocks in which the symbols in each slice unit are separated by exactly i symbols. Symbols in a string of i incoming symbols are compared by i comparators in parallel with symbols previously stored in the slice units to identify matching sequences of symbols. A control unit controls execution of the sequential algorithm to condition the comparators to scan symbols in parallel but in each of the blocks sequentially and cause matching sequences and nonmatching sequences of symbols to be stored in the array. The parameters i and j are selected to limit the number of comparators required to achieve a desired degree of efficiency in executing the algorithm based upon a trade-off of algorithm execution speed versus hardware cost. A priority encoder calculates from signals output by the slice units each j,i address in which a matching sequence is identified, but it outputs the address of only one (such as the smallest) of these addresses.

公开(公告)号：SG45378A1

公开(公告)日：1998-01-16

申请号：SG1996005250

申请日：1989-06-08

Applicant: IBM

Inventor： CHEVION DAN SAMUEL ,  KARNIN EHUD DOV ,  WALACH EUGENIUSZ

IPC: H03M7/40

Abstract: An improved method is disclosed for generating a compressed representation of a source data string each symbol of which is taken from a finite set of m + 1 symbols, a0 to am . 'The method is based on an arithmetic coding procedure wherein the compressed representation is recursively generated as successive sub-intervals within a predetermined interval. The width of each sub-interval is theoretically equal to the width of the previous sub-interval multiplied by the probability of the current symbol. The improvement is achieved by approximating the width of the previous sub-interval so that the approximation can be obtained by a single shift and add operation using a suitable shift register.

公开(公告)号：DE68926270D1

公开(公告)日：1996-05-23

申请号：DE68926270

申请日：1989-06-08

Applicant: IBM

Inventor： CHEVION DAN SHMUEL ,  KARNIN EHUD DOV ,  WALACH EUGENIUSZ

IPC: H03M7/40

Abstract: An improved method is disclosed for generating a compressed representation of a source data string each symbol of which is taken from a finite set of m + 1 symbols, a0 to am . 'The method is based on an arithmetic coding procedure wherein the compressed representation is recursively generated as successive sub-intervals within a predetermined interval. The width of each sub-interval is theoretically equal to the width of the previous sub-interval multiplied by the probability of the current symbol. The improvement is achieved by approximating the width of the previous sub-interval so that the approximation can be obtained by a single shift and add operation using a suitable shift register.

公开(公告)号：CA2019134C

公开(公告)日：1996-04-09

申请号：CA2019134

申请日：1990-06-15

Applicant: IBM

Inventor： CHEVION DAN SHMUEL ,  KARNIN EHUD DOV ,  WALACH EUGENIUSZ

IPC: G06T9/00 ,  H04N1/411 ,  G06K9/36

Abstract: This method relates to the compression of information contained in filled-in forms (O) by separate handling of the corresponding empty forms (CP) and of the information written into them (VP). Samples of the empty forms are prescanned, the data obtained digitized and stored in a computer memory to create a forms library. The original, filled-in form (O) to be compressed is then scanned, the data obtained digitized and the retrieved representation of the empty form (CP) is then subtracted, the difference being the digital representation of the filled-in information (VP), which may now be compressed by conventional methods or, preferably, by an adaptive compression scheme using at least two compression ratios depending on the relative content of black pixels in the data to be compressed.