Hadamard Transform-Based Optimized HEVC Video Coding

The High Efficiency Video Coding (HEVC/H.265) standard achieves great improvement in compression efficiency over the widely used H.264/AVC standard at a cost of much higher complexity. When encoding videos using HEVC, the selection of the quantization parameter (QP) can significantly affect the coding efficiency. Typical algorithms for adaptive quantization employ fixed bitrate budgeting or fixed QP offsets for different frames and different blocks, without considering detailed input video characteristics, some of which might be captured using computer vision methods. The problem of determining adaptive settings of HEVC coding parameters has not been satisfactorily solved. In this paper, we proposed a Hadamard ("HAD") energy-based optimized HEVC video encoder, in which HAD energy is used to measure the amount of residual information to be encoded in a block so as to determine the QP value for each block for a better coding efficiency. HAD energy is also used to expedite the time-consuming mode decision process and for a precise scene change detection to avoid flicker artifacts. Experiment using the widely used open source HEVC encoder x265-v1.8 showed that the proposed algorithm was able to achieve an average of 14% saving in Bjontegaard-delta-rate and an average of 20% saving in encoding time as compared the " medium" preset of x265, while the proposed algorithm also produced an improvement of 3.3% in coding efficiency for the HEVC reference software HM-16.6.