JPH06324924A - Data compressing device - Google Patents

Abstract

(57) [Abstract] [Purpose] To obtain a data compression apparatus which enables compression suitable for data to be compressed and which makes variable compression conditions for a series of data. [Structure] Means 13 for setting the size of data to be read at one time as a compression condition and the number of partial data obtained by subdividing the read data, means 14 for dividing the read data into the partial data, and each divided portion. The means 15 for comparing the data with the partial data of the next read data, the means 16 for calculating the count of each partial data based on the comparison result, and the data compressed from the count result are set as described above. A writing means 6 is provided together with the compression condition. [Effect] The redundancy of the compression target data is increased, and optimal data compression can be realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data compression device for compressing and storing data in a data storage device.

[0002]

2. Description of the Related Art Conventionally, a run length method has been used as a data compression method in which there are few kinds of signals and long runs of the same symbol often appear. FIG. 3 is a block flowchart of a conventional data compression device. In the figure,
Reference numeral 1 is first data, 2 is a data compression device, 3 is data reading means, 4 is record comparing means, 5 is record counting means, and 6 is data writing means for writing second data 7. FIG. 4 is a diagram showing an example of data compressed by a conventional compression device. In the figure, 8a is the first record, 8b is the second record, and 9 is the first data 1.
Of the same record in, 10 is a code indicating the start of compression,
Reference numeral 11 is the number of repetitions of the same record, and 12 is one record in the sequence 9 of the same record.

Next, the operation will be described. First, the data reading means 3 reads the first data 1 on a record-by-record basis. Next, the record comparison means 4 compares the second record 8b with the immediately preceding first record 8a. When the second record 8b is the same as the first record 8a, it is considered that the array 9 of the same records is detected, and the record counting means 5 counts the number of repetitions of the same record. When the second record 8b is different from the first record 8a, it is considered that the end of the array 9 of the same record is detected, the second data 7 is written by the data writing means 6, and the number of repetitions 11 of the same record is set to the initial value. Return to. At this time, if the number of repetitions 11 of the same record is smaller than a predetermined number, the first record 8a for the same number of times as the number of repetitions 11 of the same record is written as the second data 7. If the number of repetitions 11 of the same record exceeds a predetermined number, the code 10 indicating the start of compression, the number of repetitions 11 of the same record and the first record 12 for one time are written as the second data 7. . In this case, a plurality of records will be compressed into one record. Data is compressed by repeating the above operation.

[0004]

Since the conventional data compression apparatus is configured as described above, the data to be compressed is such that similar records are continuous or each record changes regularly. However, there is a problem that data compression cannot be performed because the same record sequence is not detected. Further, if the compression condition is changed according to individual data, the decompression condition also needs to be changed accordingly, which makes efficient work impossible.

The present invention has been made in order to solve the above-mentioned problems, and it is possible to perform compression suitable for the type of data, and a data compression apparatus that can change the compression condition for a series of data. Aim to get.

[0006]

A data compression apparatus according to the present invention comprises means for setting the size of data to be read at one time, means for setting the number of partial data obtained by subdividing the input first data, Means for dividing the first data into the partial data, means for comparing each divided partial data with partial data of the next read data, means for calculating the count of each partial data based on the comparison result , And compress the data from this counting result,
Means for writing the second data together with the conditions of the set data size and the number of partial data are provided.

[0007]

In the present invention, data compression is performed for each partial data by arbitrarily setting the size of the data to be read at one time and the number of partial data obtained by subdividing the input data.

[0008]

【Example】

Example 1. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block flow chart showing an embodiment of the present invention. In the figure, 1 to 3 and 6 to 7 are the same as or equivalent to those of the conventional one. A data compression condition setting unit 13 can arbitrarily set a compression condition suitable for the data to be compressed. Reference numeral 14 is a data dividing unit that divides the read data according to the set compression condition, 15 is a divided data comparing unit that compares the data divided by the data dividing unit 14 with the next divided data, 16
Is a divided data counting means for calculating the number of repetitions of divided data.

Next, the operation will be described with reference to the character data example shown in FIG. First, the data compression condition setting means 13 sets the number of records to be read at one time, the number of partial data obtained by subdividing the records, a code indicating the start of compression, and the maximum number of repetitions of the same partial data, in accordance with the compression target data. . However, the partial data that can be subdivided refers to the partial data that can be subdivided so as to obtain the most repetitions of the same data based on the arrangement and regularity of the data to be compressed. The data reading means 3 reads the first data 1 by the set number of records. Data dividing means 14
Divides the read data in record units based on the number of records. Further, the data of one record is divided into the number based on the set number of partial data. Next, the divided data comparison means 15 compares the divided partial data (divided data) with the partial data of the next record. For example, the character data 1 before compression shown in FIG.
7, the number of partial data is 4, the first record 18 is divided into 18a, 18b, 18c and 18d, and the second record 19 is divided into 19a, 19b, 19c and 19d. 15 is 18a and 19a, 18
b and 19b, 18c and 19c, 18d and 19d are compared.

Next, based on the result of comparison of the divided data, the data writing means 6 writes the compressed data. 2A, it is assumed that the first record 18 and the second record 19 have different partial data. In addition, subsequent records 20, 21, 2
It is assumed that 2 and 23 are the same record. Reference numeral 24 is a row of the same records. FIG. 2B shows the data after compression. At the beginning, the number of records 25 read at once set by the compression condition setting means 13, the number of partial data 26, the code 27 indicating the start of compression, and the same portion are shown. The maximum number of data repetitions 28 is written. continue,
Since the record 18 is different from the record 19 for all partial data, the data of the record 18 is written.

Next, the record 19 and the record 20 are similarly compared. If all the partial data are the same, the same data is repeated from record 19 to record 23, and the divided data counting means 16 calculates the number of repetitions 29 (= 5). If the calculated number of iterations is less than or equal to the maximum number of iterations 28,
Compression start code 27, number of repetitions of the same data 29 (=
5) and the partial data 19a are written in this order. Similarly,
It is also written for 19b, 19c, and 19d. When the calculated number of repetitions exceeds the maximum number of repetitions 28, the number of repetitions 29 is written in two so that the number of repetitions falls within the maximum number of repetitions 28. Thereafter, the above operation is repeated to perform data compression, and the data is stored as the second data 7. Also, from the second data 7 to the first
Data 1 can be easily restored based on the compression condition written at the beginning of the second data. Therefore,
Even if the compression condition is changed and the data is compressed again, the decompression operation does not change, and the optimum data compression can be realized.

The above is the description of the data example shown in FIG. 2B. In the comparison between the records 19 and 20, if only one set of 19a and 20a is the same,
If three sets of 9b and 20b, 19c and 20c, 19d and 20d are different, the same data is repeated 19 times.
a to 23a, the compression start code 27, the same data repetition number 29 (= 5),
After writing the partial data 19a, 19b, 20b, ...
., 23b, 19c, 20c, ..., 23c, 19d,
20d, ..., 23d are written in this order.
As described in the above operation description, it is possible to arbitrarily set and change the compression condition (partial data division that increases the number of repetitions of the same data) that matches the compression target data,
Optimal data compression can be realized.

[0013]

As described above, according to the present invention, as the compression condition, the size of data read at one time and the number of partial data can be arbitrarily set according to the data to be compressed. Redundancy increases and data compression rate improves. Further, since the set compression condition is stored together with the compressed data, there is an effect that the data can be easily restored even if the compression condition is changed and the optimum data compression can be realized.

[Brief description of drawings]

FIG. 1 is a block flowchart showing a data compression apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of compression of character data according to an embodiment of the present invention.

FIG. 3 is a block flowchart showing a conventional data compression device.

FIG. 4 is a diagram showing an example of data compression by a conventional data compression device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st data 2 Data compression apparatus 3 Data reading means 6 Data writing means 7 2nd data 13 Data compression condition setting means 14 Data dividing means 15 Divided data comparing means 16 Divided data counting means

Claims (1)

[Claims] 1. A data compression apparatus for inputting first data, compressing the data, and writing the data as second data to a data storage device, means for setting a size of data to be read at one time, Means for setting the number of partial data formed by subdividing the data, means for dividing the first data into the partial data, means for comparing each divided partial data with partial data of the next read data, A means for calculating the count of each partial data based on the comparison result, and
A data compressing device comprising means for compressing data from the counting result and writing the data as the second data together with the conditions of the set data size and the number of partial data.