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variable length coding (VLC)

Variable Length Coding (VLC) is a compression method in which data with a fixed number of bits is replaced by symbols with a variable number of bits. It is a lossless compression in which the frequency of recurring symbols is taken into account in the coding. Thus, symbols that occur frequently, such as the letter "e", are represented with a few bits, while others that occur rarely are represented with more bits. The compression method is thus comparable to run-length coding in terms of its approach.

In variable length coding, the bits are represented as a compressed bit sequence. Such a bit sequence could look like this: 01001 etc. Since the VLC coding converts the most frequently occurring letters or digits with one bit, the others with two, three and four bits, the represented bit sequence cannot be decoded. For this reason, the individual characters of the bit sequence are delimited from each other by a delimiter. The coded bit sequence could then look like this: 0#10#0#1, where the 0 stands for the letter "e", the 1 for "l" and the 10 for "d".

Example for Variable Length Coding (VLC)

Example for Variable Length Coding (VLC)

The coding of the word "noble" thus consists of 8 characters, whereas in binary transmission, depending on the code used, the number of bits is much higher.

Englisch: variable length coding - VLC
Updated at: 28.10.2011
#Words: 209
Links: compression, method, data, frequency (f), account
Translations: DE

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