High-Level Synthesis Implementation of an Embedded Real-Time HEVC Intra Encoder on FPGA for Media Applications

High Efficiency Video Coding (HEVC) is the key enabling technology for numerous modern media applications. Overcoming its computational complexity and customizing its rich features for real-time HEVC encoder implementations, calls for automated design methodologies. This article introduces the first complete High-Level Synthesis (HLS) implementation for HEVC intra encoder on FPGA. The C source code of our open-source Kvazaar HEVC encoder is used as a design entry point for HLS that is applied throughout the whole encoder design process, from data-intensive coding tools like intra prediction and discrete transforms to more control-oriented tools such as context-adaptive binary arithmetic coding (CABAC). Our prototype is run on Nokia AirFrame Cloud Server equipped with 2.4 GHz dual 14-core Intel Xeon processors and two Intel Arria 10 PCIe FPGA accelerator cards with 40 Gigabit Ethernet. This proof-of-concept system is designed for hardware-accelerated HEVC encoding and it achieves real-time 4K coding speed up to 120 fps. The coding performance can be easily scaled up by adding practically any number of network-connected FPGA cards to the system. These results indicate that our HLS proposal not only boosts development time, but also provides previously unseen design scalability with competitive performance over the existing FPGA and ASIC encoder implementations.