A Deeply Pipelined CABAC Decoder for HEVC Supporting Level 6.2 High-Tier Applications

摘要

High Efficiency Video Coding (HEVC) is the latest video coding standard that specifies video resolutions up to 8K ultra-high definition (UHD) at 120 frames/s to support the next decade of video applications. This results in high-throughput requirements for the context-adaptive binary arithmetic coding (CABAC) entropy decoder, which was already a well-known bottleneck in H.264/AVC. To address the throughput challenges, several modifications were made to CABAC during the standardization of HEVC. This paper leverages these improvements in the design of a high-throughput HEVC CABAC decoder. It also supports the high-level parallel processing tools introduced by HEVC, including tile and wavefront parallel processing. The proposed design uses a deeply pipelined architecture to achieve a high clock rate. Additional techniques such as the state prefetch logic, latched-based context memory, and separate finite state machines are applied to minimize stall cycles, while multibypass-bin decoding is used to further increase the throughput. The design is implemented in an International Business Machines 45-nm silicon on insulator process. After place and route, its operating frequency reaches 1.6 GHz. The corresponding throughputs achieve up to 1696 and 2314 Mbin/s under common and theoretical worst-case test conditions, respectively. The results show that the design is sufficient to decode in real-time high-tier video bitstreams at level 6.2 (8K UHD at 120 frames/s), or main-tier bitstreams at level 5.1 (4K UHD at 60 frames/s) for applications requiring subframe latency, such as video conferencing.