Fast Line-Based Intra Prediction for Video Coding

Intra prediction plays a very important role in current video coding technologies like the H.265/High Efficiency Video Coding (HEVC) standard, the Joint Exploration Test Model (JEM) and the upcoming Versatile Video Coding (VVC) standard. In previous work we proposed a Line-Based Intra Prediction algorithm to improve the state-of-art coding performance of HEVC and JEM. This method divides (horizontally or vertically) a block into lines and then it codes each of them individually in a sequential manner. At the encoder side, however, it is necessary to select an optimal combination of intra mode and 1-D split type in a Rate-Distortion sense. Since testing for every block all possible combinations of these two parameters would imply a very significant increase in the encoder complexity, this paper proposes several fast algorithms to reduce the number of tests and improve the overall trade-off between complexity and gain. The experimental results show a reduction of the encoder run-time from 322% to 166% in exchange for a loss of 0.34% for the All Intra configuration and from 151% to 116% for a loss of 0.15% in the case of Random Access.