A high performance HEVC de-blocking filter and SAO architecture for UHDTV decoder

High efficiency video coding (HEVC) is the next generation video compression standard. In-loop filter is an important component of HEVC which is composed of two parts, deblocking filter (DBF) and sample adaptive offset (SAO). In this article, we propose a high performance in-loop filter architecture for HEVC which integrate both deblocking filter and SAO. To achieve it, several ideas are adopted. Firstly, SAO is processed based on drifted block, which suits the output pattern of deblocking filter and ease the coupling of deblocking filter and SAO. Secondly, luma and chroma samples of each 4x4 block are organized in same memory storage unit and they are processed simultaneously to raise the parallelism. Thirdly, in both deblocking filter and SAO, calculation core is implemented in combinational logic and data storage is implemented in register groups. Calculation core keeps processing data continually, which greatly raises the utilization of DBF core and SAO core. Fourthly, task level pipeline in processing 8x8 block is employed between deblocking filter and SAO. By these means, a high performance in-loop filter including both deblocking filter and SAO is achieved without any intermediate storage or circuit. It takes only four cycles to finish the deblocking filter and SAO of one 8x8 block. The implementation results show that the proposed solution can be synthesized to 240 MHz with 65 nm technology. Thus this solution can process 3.84G pixels/s at maximum. UHDTV 4320p (7680 X 4320) @ 60fps decoding can be realized with 124.4 MHz working frequency by the proposed architecture.