Showing papers on "Run-length encoding published in 1989"

Adaptive data compression apparatus including run length encoding for a tape drive system

Abstract: The adaptive data compression apparatus is located within a tape drive control unit which is interposed between one or more host computers and one or more tape transports. The adaptive data compression apparatus functions to efficiently compress a user data file received from a host computer into a bit oriented compressed format for storage on the magnetic tape that is loaded in the tape transport. The data compression apparatus divides each block of an incoming user data file into predetermined sized segments, each of which is compressed independently without reference to any other segment in the user data file. The data compression apparatus concurrently uses a plurality of data compression algorithms to adapt the data compression operation to the particular data stored in the user data file. A cyclic redundancy check circuit is used to compute a predetermined length CRC code from all of the incoming user data bytes before they are compressed. The computed CRC code is appended to the end of the compressed data block. The data compression apparatus operates by converting bytes and strings of bytes into shorter bit string codes called reference values. The reference values replace the bytes and strings of bytes when recorded on the magnetic tape. The byte strings have two forms, a run length form for characters that are repeated three or more times, and a string form that recognizes character patterns of two or more characters.

Data compression system for successively applying at least two data compression methods to an input data stream

Abstract: The improved data compression system concurrently processes both strings of repeated characters and textual substitution of input character strings. In this system, the performance of data compression techniques based on textual substitution are improved by the use of a compact representation for identifying instances in which a character in the input data stream is repeated. This is accomplished by nesting a run length encoding system in the textual substitution system. This structure adds the recognition of runs of a repeated character before the processor performs the textual substituted data compression operation. A further performance improvement is obtained by expanding the alphabet of symbols stored in the compressor's dictionary to include both the characters of the input data stream and repeat counts which indicate the repetition of a character. The handling of these repeat counts by the textual substitution based compression technique is no different than the handling of characters, or certain modifications are made in the handling of repeat counts.

Apparatus for image data transposition and compression/decompression

Abstract: An application specific integrated circuit (ASIC) allows for the transposition, compression, and decompression of acquired image video data The transposition method associated with this ASIC provides for the reordering of received vertically scanned columns of acquired pixel image data into horizontal rows and provides for the deleting of overscan and underscan pixel data associated with each of the vertically scanned columns of acquired data This transposed data is then compressed employing Huffman encoding techniques in conjunction with run length encoding The compression/decompression apparatus and method of this invention utilizes a reordering technique whereby all of the 'high confidence' predictions are placed in one end of the buffer and all the 'low confidence' predictions are placed in another end of the same buffer This reordering, together with the biased window configuration and associated run length count definition, allows for high efficiency lossless compression and decompression of associated image data

Encoding system for picture signal and its apparatus

Abstract: PURPOSE:To improve the efficiency of encoding by outputting a run length code with the shortest code length among plural run length codes and an identification signal in the scanning order corresponding to the run length code in the unit of blocks. CONSTITUTION:A conversion section 3 reads n-set of scanning tables in order and sends a linear picture signal converted according to each individual scanning table to a run length encoding section 4 sequentially. The run length encoding section 4 uses the length of the consecutive white picture elements and black picture elements with respect to the received linear picture signal from the conversion section 3 as a run length so as to count it and the code corresponding to the run length is generated and the run length code is generated to one- block picture signal and sent to a code storage section 6 and the code length (bit number) of the run length code is sent to the code length storage section 5. The run length encoding section 4 applies processing to each of linear pictures signals (n-set) subject to conversion by using n-set of scanning tables.