A method of context adaptive binary arithmetic coding and decoding groups a plurality N binary symbols in corresponding syntax elements and divides a range into 2N subranges based upon corresponding contexts. The invention encodes data by selecting an offset determined by the probability states of the context of the N binary symbols. Decoding is similar with the place of the coded offset within the 2N subranges determining the syntax decoding. When the total number of binary symbols to be coded does not equal an integral multiple of N, the invention codes dummy binary symbols at the end of a grouping of a plurality N binary symbols. Probability state updates occur only following every N binary symbols.