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Context-adaptive binary arithmetic coding
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<p>Context-adaptive binary arithmetic coding (CABAC) is a form of <a href="/facts/Entropy_encoding/44I0n8F8">entropy encoding</a> used in the <a href="/facts/H.264%2fMPEG-4_AVC/soCzKcmJ">H.264/MPEG-4 AVC</a> and <a href="/facts/High_Efficiency_Video_Coding/6gp7DC1a">High Efficiency Video Coding</a> (HEVC) standards. It is a <a href="/facts/Lossless_compression/LS702KsN">lossless compression</a> technique, although the video coding standards in which it is used are typically for <a href="/facts/Lossy_compression/jHW7DDv3">lossy compression</a> applications. CABAC is notable for providing much better <a href="/facts/Data_compression/gMFuY4FT">compression</a> than most other entropy encoding algorithms used in video encoding, and it is one of the key elements that provides the H.264/AVC encoding scheme with better compression capability than its predecessors. </p><p>In <a href="/facts/H.264%2fMPEG-4_AVC/soCzKcmJ">H.264/MPEG-4 AVC</a>, CABAC is only supported in the Main and higher <a href="/facts/H.264%2fMPEG-4_AVC/soCzKcmJ">profiles</a> (but not the extended profile) of the standard, as it requires a larger amount of processing to decode than the simpler scheme known as <a href="/facts/Context-adaptive_variable-length_coding/f6auheYI">context-adaptive variable-length coding</a> (CAVLC) that is used in the standard's Baseline profile. CABAC is also difficult to parallelize and vectorize, so other forms of parallelism (such as spatial region parallelism) may be coupled with its use. In HEVC, CABAC is used in all profiles of the standard. </p>