Context-adaptive binary arithmetic coding

The context modeling is responsible for most of CABAC's roughly 10% savings in bit rate over the CAVLC entropy coding method.

When the total number of occurrences of a model exceeds a threshold value, the frequency counts for "0" and "1" will be scaled down, which in effect gives higher priority to recent observations.

In 1986, IBM researchers Kottappuram M. A. Mohiuddin and Jorma Johannes Rissanen filed a patent for a multiplication-free binary arithmetic coding algorithm.

Lu, W. B. Pennebaker, L. Mitchell and G. G. Langdon presented an adaptive binary arithmetic coding (ABAC) algorithm called Q-Coder.

[7][8] The above patents and research papers, along several others from IBM and Mitsubishi Electric, were later cited by the CCITT and Joint Photographic Experts Group as the basis for the JPEG image compression format's adaptive binary arithmetic coding algorithm in 1992.

[10] The first reported use of adaptive binary arithmetic coding in motion video compression was in a proposal by IBM researchers to the MPEG group in 1989.

In 1999, Youngjun Yoo (Texas Instruments), Young Gap Kwon and Antonio Ortega (University of Southern California) presented a context-adaptive form of binary arithmetic coding.

[13] The modern context-adaptive binary arithmetic coding (CABAC) algorithm was commercially introduced with the H.264/MPEG-4 AVC format in 2003.

[14] The majority of patents for the AVC format are held by Panasonic, Godo Kaisha IP Bridge and LG Electronics.