Context Adaptive Binary Arithmetic Coding

CABAC ( Context Adaptive Binary Arithmetic Coding -based ) describes an effective way of lossless compression of binary files. The reference algorithm for CABAC was developed by the ITU- T and the ISO / IEC in the course of standardization of the video codec MPEG-4/Part10 ( H.264/AVC ).

As the name suggests, it is in CABAC a specialized binary arithmetic coder, the coding tables can change its context-dependent. Like all arithmetic encoder is also a CABAC entropy coder. In comparison with the known entropy coding Huffman, CABAC cuts off much better, but is also many times more computationally intensive.

The broken letters CABAC

Context -based adaptive ( CABAC ) coding refers to the ability of the encoder to be able to dynamically adjust its coding tables during the encoding process to the coding material.

Binary ( CABAC ) coding indicates that this encoder only works for binary data. Data available in a different format, must be converted to a binary representation first.

Arithmetic Coding ( CABAC ) is a highly effective form of entropy coding.

CABAC and H.264

In the sections " Main Profile " and " High Profile " of the video standards MPEG-4/Part10 ( H.264/AVC ) CABAC is used, where it is partly responsible for the good image quality, high compression rate and the high computing power.

In the lower profiles of the video coding standard H.264 the simpler CAVLC ( Context Adaptive Variable Length Coding) is used.