Data compression apparatus and method

• US 5,146,221 A
• Filed: 11/27/1990
• Issued: 09/08/1992
• Est. Priority Date: 01/13/1989
• Status: Expired due to Fees

• Current Assignee: Hifn, Inc. (Maxlinear Incorporated)
• Original Assignee: Stac, Inc. (Titan Corporation)
• Inventors: Whiting, Douglas L., Ivey, Glen E., George, Glen A.
• Primary Examiner(s): Logan, Sharon D.
• Application Number:
  US07/619,291
• Time in Patent Office: 651 Days
• Field of Search: 341/67, 341/106, 341/51, 341/95, 341/87, 364/200MS File, 364/900 MS File
• US Class Current: 341/67
• CPC Class Codes: G06T 9/005 Statistical coding, e.g. Huffman, run length coding
• CPC Class Codes: H03M 7/3086 employing a sliding window, e.g. LZ77
• CPC Class Codes: H03M 7/40 Conversion to or from variable length codes, e.g. Shannon-Fano code, Huffman code, Morse code
• CPC Class Codes: H03M 7/46 Conversion to or from run-length codes, i.e. by representing the number of consecutive digits, or groups of digits, of the same kind by a code word and a digit indicative of that kind

Abstract

An apparatus and method are disclosed for converting an input data character stream into a variable length encoded data stream in a data compression system. The data compression system includes a history array. The history array has a plurality of entries and each entry of the history array is for storing a portion of the input data stream. The method for converting the input data character stream includes the following steps. Performing a search in a history array for the longest data string which matches the input data string. If the matching data string is found within the history buffer, the next step includes encoding the longest matching data string found by appending to the encoded data stream a tag indicating the longest matching data string was found and a string substitution code. If the matching data string is not found within the history array, the next step includes encoding the first character of the input data string by appending to the encoded data stream a raw data tag indicating that no matching data string was found and the first character of the input data string.

Claims

1. An apparatus for converting an input data stream into a variable length encoded data stream, said apparatus comprising:

a single RAM configuration comprising;

a history array having a plurality of entries, each of said plurality of entries for storing previously processed segments of said input data stream, and

a FIFO data buffer for buffering data transfers to and/or from said apparatus;

a single address bus for addressing said history array and said FIFO data buffer, said single address bus coupled to said single RAM configuration; and

a data compression system, said data compression system coupled to said single address bus, said data compression system comprising;

means for performing a search of said history array for a string of said previously processed segments of said input data stream which matches said input data stream, and

encoding means for encoding said matching string found in said history array.

2. An apparatus for converting an input data stream into a variable length encoded data stream, said apparatus comprising:

a single RAM configuration comprising;

means for storing previously processed segments of said input data stream, and

a FIFO data buffer for buffering data transfers to and/or from said apparatus;

a single address bus for addressing said means for storing and said FIFO data buffer, said single address bus coupled to said single RAM configuration; and

a data compression system, said data compression system coupled to said single address bus, said data compression system comprising;

means for performing a search in said storing means for a string of said previously processed segments of said input data stream which matches said input data steam, and

encoding means for encoding said matching string found in said storing means.