1. Introduction
The past decade has witnessed an explosive growth of video data delivered over Internet. Such a growth poses a great challenge on the efficiency of video coding. To significantly improve the efficiency of video coding, the High Efficiency Video Coding (HEVC) standard [1] was approved in April, 2013. It has been verified that HEVC can reduce the bit-rate to around 50% with similar visual quality, compared with its former standard H.264/AVC. However, the cost for the high coding efficiency is much more computational complexity [2]. This cost becomes a great obstacle of video encoding and decoding on portable devices with limited power.