Fast Intra Prediction for High Efficiency Video Coding

Emerging High Efficiency Video Coding (HEVC) video coding standard promises the significant compression performance improvement compared to the H.264/AVC. However it comes with the tremendous encoding complexity increase. Thus, it is very useful and necessary to develop fast algorithms for HEVC, so as to reduce the encoder complexity. In this paper, we propose a fast intra prediction scheme for HEVC to reduce the prediction mode search for each prediction unit. For all available test sequences provided by the JCT-VC, it demonstrates 38% encoding time reduction for all intra case with BD-RATE increase about 2.9%. Several sub-algorithms are developed and integrated for complexity reduction. First, we applied the Hadamard transform on 2:1 downsampled prediction residual to derive the sum of absolute Hadamard transformed difference (SATD) for rough mode decision, where a progressive search process is then used to reduce effective mode candidates for fully rate-distortion optimized quantization (RDOQ). Finally, an early termination based on SATD cost and mode distances is also included in RDOQ process to further complexity reduction. Extensive simulation results demonstrate that our proposed method is quite efficient for intra mode prediction speed-up. Our proposal is complementary to other separated works on fast coding unit, prediction unit, and transform unit decision. We expect more encoder complexity reduction by combing our solution and other fast algorithms.