A Heterogeneous HEVC Video Encoder System Based on Two-Level CPU-FPGA Computing Architecture.

To trade off the speed and quality of video encoding, the heterogeneous methods to compress video have become a research hotspot. This paper proposes a CPU-FPGA HEVC video encoder system based on OpenPOWER platform. For software, x265 is optimized by instruction replacement and binding, which achieves 24.5% average encoding performance improvement. For hardware, some functions of x265 are implemented as hardware accelerators in two levels. Frame-level acceleration implements the whole inter encoder on two FPGAs and supports 4K@75fps real-time video encoding. For functional-unit-level acceleration, some sub-functions of x265, such as 32×32 blocks of inverse discrete cosine transform (IDCT) and fractional motion estimation (FME), are implemented to achieve encoding performance improvement without video quality loss.