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They are also known as Lempel-Ziv 1 (LZ1) and Lempel-Ziv 2 (LZ2) respectively. [3] These two algorithms form the basis for many variations including LZW , LZSS , LZMA and others. Besides their academic influence, these algorithms formed the basis of several ubiquitous compression schemes, including GIF and the DEFLATE algorithm used in PNG and ...
gzip is a file format and a software application used for file compression and decompression.The program was created by Jean-loup Gailly and Mark Adler as a free software replacement for the compress program used in early Unix systems, and intended for use by GNU (from which the "g" of gzip is derived).
The LZ4 algorithm aims to provide a good trade-off between speed and compression ratio. Typically, it has a smaller (i.e., worse) compression ratio than the similar LZO algorithm, which in turn is worse than algorithms like DEFLATE.
The scenario described by Welch's 1984 paper [1] encodes sequences of 8-bit data as fixed-length 12-bit codes. The codes from 0 to 255 represent 1-character sequences consisting of the corresponding 8-bit character, and the codes 256 through 4095 are created in a dictionary for sequences encountered in the data as it is encoded.
Thus, a representation that compresses the storage size of a file from 10 MB to 2 MB yields a space saving of 1 - 2/10 = 0.8, often notated as a percentage, 80%. For signals of indefinite size, such as streaming audio and video, the compression ratio is defined in terms of uncompressed and compressed data rates instead of data sizes:
1989 NeXTSTEP 1.0 pax and gzip: Yes ? ? Yes ? RPM Package Manager (RPM) .rpm Red Hat: 1995 Red Hat Linux 1.0 cpio and gzip: Yes ? ? ? 1 s Slackware Package .tgz Patrick Volkerding: 1993 Slackware 1.0 tar and gzip: Yes No No ? ? Windows Installer (also MSI) .msi Microsoft: 2000 Windows 2000: OLE Structured Storage, Cabinet and SQL: Optional ...
Decompression speed is higher than bzip2, but lower than gzip. Compression can be much slower than gzip, and is slower than bzip2 for high levels of compression, and is most useful when a compressed file will be used many times. [4] [5] XZ Utils consists of two major components: xz, the command-line compressor and decompressor (analogous to gzip)
The LZMA2 header consists of a byte indicating the dictionary size: 40 indicates a 4 GB − 1 dictionary size; Even values less than 40 indicate a 2 v/2 + 12 bytes dictionary size; Odd values less than 40 indicate a 3×2 (v − 1)/2 + 11 bytes dictionary size; Values higher than 40 are invalid