A COMPARISON OF CABAC THROUGHPUT FOR HEVC/H.265 VS. AVC/H.264

The CABAC entropy coding engine is a well known through-put bottleneck in the AVC/H.264 video codec. It was re-designed to achieve higher throughput for the latest video coding standard HEVC/H.265. Various improvements were made including reduction in context coded bins, reduction in total bins and grouping of bypass bins. This paper dis-cusses and quantifies the impact of these techniques and in-troduces a new metric called Bjøntegaard delta cycles (BD-cycle) to compare the CABAC throughput of HEVC vs. AVC. BD-cycle uses the Bjøntegaard delta measurement method to compute the average difference between the cycles vs. bit-rate curves of HEVC and AVC. This metric is useful for estimat-ing the throughput of an HEVC CABAC engine from an ex-isting AVC CABAC design for a given bit-rate. Under the common conditions set by the JCT-VC standardization body, HEVC CABAC has an average BD-cycle reduction of 31.1% for all intra, 24.3 % for low delay, and 25.9 % for random ac-cess, when processing up to 8 bypass bins per cycle. Index Terms — HEVC, H.265, AVC, H.264, CABAC, throughput, arithmetic coding 1