Method and apparatus for reducing data expansion during data compression,申请号US19990379864-传众专利搜索

Method and apparatus for reducing data expansion during data compression

申请公布号：US6281816(B1)

申请号：US19990379864

申请日期：1999.08.24

申请公布日期：2001.08.28

申请人：

INTERNATIONAL BUSINESS MACHINES CORPORATION

发明人：KAMPF FRANCIS A.

分类号：G06T9/00;H03M7/30;(IPC1-7):H03M7/00

主分类号：G06T9/00

摘要：A method and apparatus for reducing data expansion during data compression are provided that allow the coding scheme used to compress data to be swapped between two or more coding schemes. Specifically, a coding window is provided that holds data to be compressed, and the compression potential of data entering or exiting the coding window is calculated. When a first threshold compression potential sum of data entering the window is reached, the coding scheme used to compress the data within the coding window is swapped from one coding scheme to another. A new compression potential sum is set based upon the compression potential of data exiting the window. The compression potential sum comprises a running total of the compression potential of data entering the coding window; and the coding scheme used to compress data within the coding window is swapped from one coding scheme to another when the compression potential sum reaches a first predetermined value. Preferably the first predetermined value is programmable and is related to the bit cost required to swap back and forth between coding schemes. The two preferred coding schemes are ALDC Lempel-Ziv 1 coding and a pass-through coding scheme wherein raw data is passed unencoded. A coding window circuit also is provided that allows analysis of the compression potential of data in accordance with the above method.