Framework and challenges: H.265/HEVC rate control in real-time transmission over 5G mobile networks

The newly emerging video coding standard H.265/HEVC, jointly developed by ITU and ISO, is being adopted by an increasing number of applications and platforms such as YouTube, Netflix, video conferencing, live broadcasting, etc. One of the major application scenarios is live broadcasting and real-time streaming over wireless networks, where network adaptability is a major challenge due to the instability/fluctuation of network bandwidth. Rate control has always been a main research area in live video streaming over wireless networks. While rate control has been extensively studied for previous video coding standards, such as H.263 and H.264/AVC, insufficient research has been done for H.265/HEVC. Also, due to the new features, tools, data structures, and algorithms introduced in H.265/HEVC to improve its coding efficiency, the algorithmic and computational complexities of its rate control schemes are greater than all its predecessors. The increasing complexities have hindered the adoption of H.265/HEVC in its real-time streaming over mobile wireless networks, such as 4G networks and the forthcoming 5G networks. In this research, the rate control algorithms/methodologies for H.265/HEVC and the corresponding mathematical modeling of each of its components will be investigated. Our goal is to develop low-complexity and highly-efficient rate control schemes for H.265/HEVC to improve its network adaptability and enable its applications to various mobile wireless streaming scenarios. The proposed rate control framework of H.265/HEVC encoder has three major components: precise target rate estimation, accurate bitrate allocation based on textural/motion complexities, and improved rate distortion optimization (RDO). In this paper, we also discuss a number of key research problems and challenges under this framework.