公开(公告)号：US3701108A

公开(公告)日：1972-10-24

申请号：US3701108D

申请日：1970-10-30

Applicant: IBM

Inventor： LOH LOUIS S ,  MOMMENS JACQUES H ,  RAVIV JOSEF

IPC: H03M5/00 ,  H03M7/42 ,  G06F5/00

CPC classification number: H03M7/42 ,  H03M5/00

Abstract: A processor for encoding fixed-length code words into variablelength code words and for decoding variable-length code words into fixed-length code words. The fixed-length code words are assigned to a number of groups and one of several possible coding sets determined by the probability of each word occurring after a preceding word. Each of the fixed-length code words is stored in a first associative memory unit along with its group number, its coding set assignment and a number of addresses arranged in groups. An input fixed-length code word is compared in the memory and will match the corresponding fixed-length stored word. One of the addresses is read out of the memory. The particular group from which the address is read out is determined by the group number of the previously received fixed-length code word. The selected address that is read out and the coding set membership, number of the previous word is entered into a second associative memory containing all the addresses arranged in several coding sets along with the variable-length code words. A match in the second memory unit on an address and a coding set number produces a variable-length code word for the input fixed-length code word. The first memory unit also provides the group number and coding set number for the next input fixed-length code word to be encoded. Decoding is performed in a similar but reverse manner starting with the variable-length coded data being entered into the second memory.

Abstract translation: 用于将固定长度码字编码成可变长度码字并用于将可变长度码字解码为固定长度码字的处理器。 固定长度码字被分配给多个组，并且由在前一个单词之后出现的每个单词的概率确定的几个可能的编码集之一被分配。 每个固定长度码字与其组号，其编码集分配和多个地址排列地存储在第一关联存储器单元中。 输入固定长度码字在存储器中进行比较，并与相应的固定长度存储字匹配。 其中一个地址从内存中读出。 读出地址的特定组由先前接收的固定长度码字的组号决定。 读出的所选择的地址和编码集隶属度，前一个字的数字被输入到包含与可变长度码字一起排列在多个编码集中的所有地址的第二关联存储器中。 第二存储单元中的地址和编码集号的匹配产生用于输入固定长度码字的可变长度码字。 第一存储器单元还为要编码的下一个输入固定长度代码字提供组编号和编码组编号。 以可变长度编码数据输入到第二存储器中，以相似但相反的方式进行解码。

公开(公告)号：US3694813A

公开(公告)日：1972-09-26

申请号：US3694813D

申请日：1970-10-30

Applicant: IBM

Inventor： LOH LOUIS S ,  MOMMENS JACQUES H ,  RAVIV JOSEF

IPC: G06F17/18 ,  H03M7/42 ,  G11B13/00 ,  G06F7/00

CPC classification number: G06F17/18 ,  H03M7/42

Abstract: The present invention relates to a method practiceable on a general purpose electronic computer for statistically analyzing a data set and for producing a set of encoding and decoding (E/D) tables for achieving compaction of the original data set utilizing a variable length code. The method disclosed may operate under constraints of available core, desired compaction rate and speed of compaction/decompaction to produce differing sets of encoding/decoding tables depending upon the constraints imposed. The method would most normally be provided and utilized as a software package wherein the primary inputs are the data set itself and the above enumerated constraints. By utilizing a variable-length code wherein the code assignment is dependent upon the characteristic of preceding data good compaction rates may be achieved utilizing reasonable amounts of memory for the E/D tables. The method comprises three principle steps. The first is the construction of a matrix showing the probability of occurrence of every member of the data set with respect to the immediately preceding member. The second step comprises grouping various rows or columns of this matrix having similar probabilities of occurrence, the third step comprises a reordering of all of the previously grouped rows or columns and finally a second clustering into coding sets may be performed.

Abstract translation: 本发明涉及一种在通用电子计算机上可行的方法，用于对数据集进行统计分析，并用于产生用于利用可变长度码来压缩原始数据集的编码和解码（E / D）表。 所公开的方法可以在可用核心，期望的压缩速率和压缩/解压缩的约束条件下操作，以根据施加的约束产生不同的编码/解码表。 该方法通常将被提供和用作软件包，其中主要输入是数据集本身和上述列举的约束。 通过利用可变长度代码，其中代码分配取决于先前数据的特性，可以利用用于E / D表的合理数量的存储器来实现良好的压缩率。