Stac, Inc.

Stac Electronics

Glen A George

Douglas L Whiting

Glen E Ivey

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.

Data compression apparatus and method

An apparatus and method are disclosed for converting an input data character stream into a variable length encoded data stream and encoding the variable length encoded date stream according to byte length. A 2 byte length is encoded by 2 bits having the values '00'. Encoded lengths of 3 and 4 bytes are represented respectively by 2 bits having the values '01' and '10'. Byte lengths of 5 to 7 are represented by 4 bits '1100' to '1110' and so on to thereby enable an efficient procedure for encoding the length of a bit string during compression.

An apparatus and method as 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 means. The history array means has a plurality of entries and each entry of the history array means 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 means for the longest data string which matches the input data string. If the matching data string is found within the history buffer means, 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 means, 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.

An apparatus and method 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 means. The history array means has a plurality of entries and each entry of the history array means 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 means for the longest data string which matches the input data string. If the matching data string is found within the history buffer means, 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 means, 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.

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 shift register means. The shift register means has a plurality of entries and each entry of the shift register means is for storing a data character of the input data stream. The method for converting the input data character stream includes the following steps. Performing a search in the shift register means for a data string which matches the input data string. The step for performing the search includes the steps of broadcasting each input data character of the input data stream to each entry of the shift register means and comparing each input data character simultaneously with the previously stored contents of each entry of said shift register means. If the matching data string is found within the shift register means, the next step includes encoding the longest matching data string by appending to the encoded data stream a tag indicating the matching data string and a string substitution code. If the matching data string is not found within the shift register means, the next step includes encoding the first character of the input data string by appending to the encoded data stream a raw data tag and the first character of the input data string.

Data compression apparatus with shift register search means

An apparatus and/or method for generating parity digits of digital information (data) in a digital communication system is disclosed. The communication system (8) is for transferring a plurality of data intervals from an originating data source (12) to a data sink (13). Each data interval comprises one or more blocks of data and each block contains one or more bytes of data. The communication system (8) includes a temporary storage means (24) for holding the data for a limited period. Included are means for transferring (14, 40) one or more data intervals from the data source (12) to the temporary storage means (24) and means for transferring (22, 40) one of the data intervals from the temporary storage means (24) to the data sink (13) including means for calculating (72) error correcting code words associated with each data interval and means for storing (16) the error correcting code words for further processing. A gating means (18, 64) is provided for halting further transfer of the data intervals between the temporary storage means (24) and the data sink (13). The gating means (18, 64) further includes means for sending the stored code words from the means for storing (16) to the data sink (13).

Write operation with gating capability

An apparatus and/or method for generating a digital clock signal which is frequency and phase referenced to an external digital data signal is disclosed. The external digital data signal is typically subject to variations in data frequency and high frequency jitter unrelated to changes in the data frequency.

Growing community of inventors

Pasadena, CA, United States of America

Glen A George