Efficient adaptive seismic data flow lossless compression and decompression method

Patent metadata

Field	Value
Publication number	US-9900025-B2
Application number	US-201515523449-A
Country	US
Kind code	B2
Filing date	Oct 9, 2015
Priority date	Oct 29, 2014
Publication date	Feb 20, 2018
Grant date	Feb 20, 2018

Abstract

An efficient adaptive seismic data flow lossless compression and decompression method, which aims at solving the problem that data occupies the storage space and affects the transmission efficiency and is used for efficiently compressing geophysical instrument data, particularly seismic data after 24-bit analog-to-digital conversion. In the method, a data flow is compressed in a lossless mode in real time, and sampling data is adaptively compressed into 1 byte or 2 bytes or 3 bytes from original 24 bits and 3 bytes in a coding manner. Besides the foregoing data ranges, other integers that can be expressed by other 24-bit integer data with symbols are required to be expressed by 4 bytes after being operated through a compression algorithm. The method has the advantages of saving a large amount of storage space and remarkably increasing the data transmission efficiency.

First claim

What is claimed is:

1. An efficient adaptive seismic data flow lossless compression and decompression method, applied to a data acquired in a geophysical equipment for efficient compression of 24-bit analog-to-digital data within the geophysical equipment, the method comprising:
determining a size of bytes based on a size of an original data;
compressing the data into one byte if the interval of numbers is between −64 and 63;
compressing the data into two bytes if the interval of numbers is between −8192 and −65 or between 64 and 8191;
compressing the data into three bytes if the interval of numbers is between 8192 and 104875 or between −104876 and −8192;
compressing the data into four bytes if the data is 24-bit signed integer data that is outside the interval of numbers between −64 and 63 or outside the interval of numbers between −8192 and −65 or between 64 and 8191 or between 8192 and 104875 or between −104876 and −8192;
wherein in the data compression there are a required number of bytes and positive or negative values are needed to select different operators and operation codes (opcodes) for a bit operation on a plurality of specified bytes;
wherein the opcode is a binary number of the byte;
wherein there are two types of operators: one is bitwise AND (&) and the other is bitwise OR (|);
setting a specified bit position;
ignoring the bytes lower than the specified byte position and not processing said lower bytes;
deleting bytes higher than the specified byte position as invalid; wherein operators and opcodes for a first byte are different under different conditions.

2. The method according to claim 1 , wherein the compression algorithm operation is a cyclical operation performed on 3 bytes of each data sampling point; the method further comprising:
reading a byte,
determining a value of the byte;
dividing the byte into 8 compression modes for processing based on numerical size and positive or negative value of the byte,
leaving unchanged bits in terms of a magnitude of values using a core of the compression algorithm operation; and deleting redundant sign bits.

3. The method according to claim 2 , wherein the compression has the following 8 compression modes:
(1) if the data is between 000000h and 00003Fh use an end byte as a compression result in order to achieve compression in a range of 1-3 bytes; because first two bytes of the data within the interval are 00h, the first two bits of the end byte are 00;
(2) if the data is between FFFFC0h and FFFFFFh use an end byte and a BFh for a bitwise AND operation as the compression result; the end byte changes from 11bbbbbb to 10bbbbbb in order to achieve compression in 1 byte range;
(3) if the data is between 000040h and 001FFFh performing a bitwise OR operation on a middle byte and 40h; then, a result of the operation and the end byte are used as the compression result; the middle byte changes from 000bbbbb to 010bbbbb in order to achieve compression in 2 bytes range;
(4) if the data is between FFE000h and FFFFBFh use a middle byte and a DFh for the bitwise AND operation; then, a result of the operation and the end byte are used as the compression result; the middle byte changes from 111bbbbb to 110bbbbb in order to achieve compression in 2 bytes range;
(5) if the data is between 002000h and 0FFFFFh use a first byte and the 60h for the bitwise OR operation; then, a result of the operation, a middle byte, and an end byte are used together as the compression result; the first byte changes from 0000bbbb to 0110bbbb, the middle byte and end byte remain unchanged, and data occupies 3 bytes both before and after compression;
(6) if the data is between F00000h and FFDFFFh use a first byte and a EFh for the bitwise AND operation; then, a result of the operation, a middle byte, and an end byte are used together as the compression result; the first byte changes from 1110bbbb to 1111bbbb, the middle byte and end byte remain unchanged, and data occupies 3 bytes both before and after compression;
(7) if the data is between 100000h and 7FFFFFh ensure original 3 bytes do not move, and then adds 70h as a first byte; newly formed 4 bytes function as the compression operation result;
(8) if the data is between 800000h and EFFFFFh ensure the original 3 bytes do not move, and then adds F0h as the first byte; newly formed 4 bytes function as the compression operation result.

4. The method according to claim 3 , wherein modes 7 and 8 increase a number of bytes from 3 bytes in the original data to 4 bytes after the compression;
wherein in modes 6 and 7, 3 bits in addition to a sign bit are required for flag bits in “0110” and “1110,” range of positive and negative data expressed is reduced from 23-bit 0 (1) bbbbbbb bbbbbbbb bbbbbbbb to 20-bit 0 (1) 110bbbb bbbbbbbb bbbbbbbb; wherein valid data occupying a range between 20 and 23 bits is not represented by 3 bytes; in addition, added first bytes “70h” and “F0h” in modes with 4 bytes are not unusual; wherein the flag bit requires 4 bytes of compressed data in order to use judgment codes “01110” or “11110”, specifically, the first byte is represented by any number between 01110bbb and 11110bbb, and decompression byte number judgment and decompression result are not affected by any number in range between 01110bbb and 11110bbb used as the first byte.

5. The method according to claim 1 , wherein the data compression is independently operated on each data sample, not relying on other sample data, and the data stream is compressed in real-time.

6. The method according to claim 1 , further comprising:
decompressing the compressed data;
wherein when decompression operations are conducted on binary data compressed using the compression method, the number of bytes occupied are firstly determined by each data sampling point in accordance with a compression coding rule;
wherein, via a series of set decoding operations, lossless seismic compressed data are restored as 1, 2, 3, or 4 bytes to the original 24-bit 3-byte data format at any time;
wherein the step of decompressing the compressed data comprises the following sub-steps:
(1) selecting a byte using a mask determination method to determine a number of bytes in a sample data; wherein the selected byte functions as a beginning byte;
(2) recovering the byte; cutting out the data with the number of bytes as determined in Step 1, and performing the bit operation on the first byte in order to recover valid bytes; and remaining bytes are left intact;
(3) performing sign bit expansion; wherein a byte that does not affect the value is added, and only represents a symbol for the sampled data (at less than 3 bytes);
(4) restoring the sampled data to a 3-byte 24-bit format.

7. The method according to claim 6 , wherein beginning with the first byte of the compressed file or data stream, the byte is masked, using the byte with the F0h for the bitwise AND operation, wherein subsequent values are divided into 8 different modes based on the operation result.

8. The method according to claim 6 , wherein 8 different modes are as follows:
if an operation result is a value of 00h, 10h, 20h, or 30h, the operation result means that 1 byte from the original byte (including the original byte) is a positive data sampling point that is taken as an end byte, then, by adding 00h as a middle byte and 00h as a first byte, there are 3 bytes that function as a decompression result (which is a same value as a value before compression);
if the operation result is a value of 80h, 90h, A0h, or B0h, the operation result means that 1 byte from the original byte (including the original byte) is a negative data sampling point, by using the original byte and the C0h for a bitwise OR operation, the result is used as an end byte, by adding FF

Assignees

• Inst Geology & Geophysics Cas

Inventors

• Xu Shanhui
• Guo Jian
• Yang Changchun
• Liu guangding

Classifications

• H04B1/66

  for reducing bandwidth of signals; for improving efficiency of transmission (H04B1/68 takes precedence) · CPC title

• H03M7/70

  Type of the data to be coded, other than image and sound · CPC title

• G01V11/00

  Prospecting or detecting by methods combining techniques covered by two or more of main groups G01V1/00 - G01V9/00 · CPC title

• H03M7/30 Primary

  Compression (speech analysis-synthesis for redundancy reduction G10L19/00; for image communication H04N); Expansion; Suppression of unnecessary data, e.g. redundancy reduction · CPC title

• G01V1/28

  Processing seismic data, e.g. for interpretation or for event detection (G01V1/48 takes precedence) · CPC title