Abstract
Aiming at the problems that the strategy of target bit allocation at the CTU layer has deviations from the human subjective observation mechanism, and the update phase of parametric model has a higher complexity in the JCTVC-K0103 rate control algorithm of ITU-T H.265/high efficiency video coding (HEVC) standard. Optimized rate control (ORC) algorithm of ITU-T H.265/HEVC based on region of interest (ROI) is proposed. Firstly, the algorithm extracts the region of interest of video frames based on time and space domains by using the improved Itti model. Then, the weight of target bits w is recalculated based on space-time domains to improve the rate control accuracy, and the target bits are distributed based on ROI by the adaptive weight algorithm once again to make the output videos more attuned with the human visual attention mechanism. Finally, the quasi-Newton algorithm is used to update the rate distortion model, which reduces the computational complexity in the update phase of the parametric model. The experimental results show that the ORC algorithm can obtain a better subjective quality in the compressed results with less bit error compared with the other two algorithms. Meanwhile, the rate distortion performance of the ORC algorithm is better on the premise of guaranteeing rate control performance.
Highlights
With the improvement of videos in the aspects of clarity and quality, the traditional video coding standard already cannot meet the coding requirements of high resolution videos
In order to catch up with the developed trend of high resolution videos and the requirements of coding technology, the video coding joint working group JCT-VC (Joint Collaborative Team on Video Coding) has developed a new video coding standard based on ITU-T H.264/AVC in 2010, named ITUT H.265/High Efficiency Video Coding (HEVC) standard [1]. e rates can be reduced by more than 50% of ITU-T H.265/HEVC compared with ITU-T H.264/AVC
JCT-VC has proposed two solutions to control the rates of ITU-T H.265/HEVC, the JCTVC-H0213 rate control algorithm based on R − Q model, and the JCTVC-K0103 rate control algorithm based on R − λ model, which are the most representative [2]. e JCTVC-K0103 rate control algorithm has better rate control effects and less fluctuation of bits compared with the JCTVC-H0213 rate control algorithm
Summary
With the improvement of videos in the aspects of clarity and quality, the traditional video coding standard already cannot meet the coding requirements of high resolution videos. The gradient descent algorithm in the update phase of rate distortion model has high computational complexity, which increases the complexity of rate control algorithm. Aiming at the shortcomings of K0103 rate control algorithm, many scholars have done a lot of research at home and abroad, which appears in the aspects of the complexity measurement of CTU and the computational load of parametric model. E above algorithms improve the performance of the parametric model to a certain extent, but the computational load reduced is not obvious. E above algorithms are improved unilaterally from the complexity measurement of CTU and the computational load of the parametric model. The rate control algorithm is optimized between the complexity measurement of CTU and weight assignments of bits at the CTU layer and the computational load of parametric model. Erefore, the overall performance of rate control algorithm is improved
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