A method and apparatus for compressing digital data that is represented as a sequence of characters drawn from an alphabet. An input data block is processed into an output data block composed of sections of variable length. Unlike most prior art methods which emphasize the creation of a dictionary comprised of a tree with nodes or a set of strings, the present invention creates its own pointers from the sequence characters previously processed and emphasizes the highest priority on maximizing the data rate-compression factor product. The use of previously input data acting as the dictionary combined with the use of a hashing algorithm to find candidates for string matches and the absence of a traditional string matching table and associated search time allows the compressor to very quickly process the input data block. Therefore, the result is a high data rate-compression factor product achieved due to the absence of any string storage table and matches being tested only against one string.

Apparatus and method for very high data rate-compression incorporating lossless data compression and expansion utilizing a hashing technique

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.

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

A method and apparatus for compressing data, particularly useful in a modem. The preferred method is implemented in a microprocessor within a modem, and dynamically adapts to changing data statistics. Parallel encoding and decoding tables are provided at the encoder and the decoder, and are updated for each character processed. Each table has a plurality of digital compression codes associated with characters of an alphabet. In response to an item of data presented for encoding, a compression code which corresponds to the character presented for encoding is selected using the encoding table. The selected compression code is provided as an output. Periodically, the association between the codes and the characters of the alphabet in the table is adjusted as a function of the frequency of occurrence of characters of the alphabet, over a plurality of characters. As the frequency of occurrence of characters presented for encoding changes, the more frequently occurring characters become associated with the shorter codes in the encoding table. By performing the same steps in the decoding table, the compression codes are used at the decoder to select a character of the alphabet, which is provided as a decoded output.

Adaptive data compression method and apparatus

Data is recorded in a data area of a disk in a hierarchical structure of program chains, programs, cells and packs, each pack is constructed by a pack header for identifying the pack and a packet having a data stream recorded therein, the packet has a packet header having a stream ID indicating at least a private stream and a sub-stream ID indicating the classification of the private stream described therein, and the classification indicates packet data of Dolby AC3 audio data, packet data of linear audio data, packet data of sub-picture data, or packet data of computer data.

Recording medium, recording apparatus and recording method for recording data into recording medium, and reproducing apparatus and reproducing method for reproducing data from recording medium

A computer storage system and processing method for indexing and accessing data stored in the computer storage system, comprising a compact multi-way search tree structure. The method employs a B-tree like search algorithm that is independent of key type or key length because all keys in index blocks are encoded by a log2M bit surrogate, where M is the maximal key length. A buffer consisting of a sorted list of key values can be directly transformed into a representation of a C0-tree.

Storage and retrieval of ordered sets of keys in a compact 0-complete tree

Method of data compression and restoration wherein an input data string including repetitive data more in number than the specified value is transformed into a data string having a format including the first region where non-compressed data are placed, the second region including a datum representative of a data string section which has undergone the compression process and information indicative of the number of repetitive data, i.e., the length of the data string section, and control information inserted at the front and back of the first region indicative of the number of data included in the first region, said transformed data string being recorded on the recording medium, and, for data reproduction, the first and second regions are identified on the basis of the control information read out on the recording medium so that the compressed data string section is transformed back to the original data string in the form of repetitive data.

Method and system for data compression and restoration

PURPOSE:To identify the 1st and the 2nd areas after data reproduction on the basis of control information indicating the number of data in the 1st area by providing the 1st area wherein uncompressed data are arrayed, the 2nd area consisting of compressed data and information on the succession number of the data, and said control information. CONSTITUTION:The (a)th-(e)th 5-byte data are recorded in an area 1 without any change in array in data format after compression as shown in figure B, and pieces of control information 2A and 2B indicating 5-byte length are recorded before and after the array. When the data are reproduced, the control information on the length of the 1st area is read out firstly all the time without reference to the access direction of a recording medium, and the 2nd area or an interblock gap appears right after the control information pairing with said information is read out, so the data are restored in either case.

Shinpei Saba

Papers

Method and system for data compression and restoration

Data compression and restoration system