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In computer science and information theory, a Huffman code is a particular type of optimal prefix code that is commonly used for lossless data compression.The process of finding or using such a code is Huffman coding, an algorithm developed by David A. Huffman while he was a Sc.D. student at MIT, and published in the 1952 paper "A Method for the Construction of Minimum-Redundancy Codes".
The optimal length-limited Huffman code will encode symbol i with a bit string of length h i. The canonical Huffman code can easily be constructed by a simple bottom-up greedy method, given that the h i are known, and this can be the basis for fast data compression. [2]
compressed file (often tar zip) using Lempel-Ziv-Welch algorithm 1F A0 ␟⍽ 0 z tar.z Compressed file (often tar zip) using LZH algorithm 2D 68 6C 30 2D-lh0-2 lzh Lempel Ziv Huffman archive file Method 0 (No compression) 2D 68 6C 35 2D-lh5-2 lzh Lempel Ziv Huffman archive file Method 5 (8 KiB sliding window) 42 41 43 4B 4D 49 4B 45 44 49 53 ...
Canonical Huffman codes address these two issues by generating the codes in a clear standardized format; all the codes for a given length are assigned their values sequentially. This means that instead of storing the structure of the code tree for decompression only the lengths of the codes are required, reducing the size of the encoded data.
LZSS improves on LZ77 by using a 1-bit flag to indicate whether the next chunk of data is a literal or a length–distance pair, and using literals if a length–distance pair would be longer. In the PalmDoc format, a length–distance pair is always encoded by a two-byte sequence.
Adaptive Huffman coding (also called Dynamic Huffman coding) is an adaptive coding technique based on Huffman coding. It permits building the code as the symbols are being transmitted, having no initial knowledge of source distribution, that allows one-pass encoding and adaptation to changing conditions in data.
Second and third bits: Encoding method used for this block type: 00: A stored (a.k.a. raw or literal) section, between 0 and 65,535 bytes in length; 01: A static Huffman compressed block, using a pre-agreed Huffman tree defined in the RFC; 10: A dynamic Huffman compressed block, complete with the Huffman table supplied; 11: Reserved—don't use.
Modified Huffman coding is used in fax machines to encode black-on-white images . It combines the variable-length codes of Huffman coding with the coding of repetitive data in run-length encoding . The basic Huffman coding provides a way to compress files with much repeating data, like a file containing text, where the alphabet letters are the ...