Speeding up Dirac’s Entropy Coder

Abstract: The Dirac codec is a new prototype video coding algorithm from BBC R&D based on wavelet technology. Compression-wise the algorithm is broadly competitive with the state-of-the-art video codecs but computational-wise the execution time is currently poor. One of the large bottlenecks is the arithmetic coder. Hence we took this part under investigation and replaced it with a faster variant, the M-coder, that is also used in the H.264/AVC codec. The resulting coder is substantially faster. We reached a convincing speedup. Thanks to an intelligent tuning of initialisation and adaption parameters the impact of the compression performance is very limited. Key-Words: Dirac video codec, arithmetic coding, M-coder