Context adaptive binary arithmetic coding, often abbreviated as CABAC, is an essential part of modern video compression. It performs lossless compression of a binary data stream without any prior knowledge of the particular characteristics of the data. These features make it an attractive algorithm for video compression because it is simple, effective, relatively fast, and requires no prior (or side band) communication between a client and server.
This project is the adaptive binary arithmetic coder used in several of my own codecs including P.264, Cairo, and Chennai.
Grab the source from this github repo.
For more information, check out this blog post.