基于对比敏感度的DASH客户端码率选择算法研究

Rate Selection Algorithm of DASH Client Based on Contrast Sensitivity

基于带宽估算的码率选择算法具有带宽利用率高的优点,但是同时也存在容易受网络波动影响造成计算出的目标码率出现瞬时峰值而造成带宽浪费的问题。针对于此,该文提出一种基于人眼对比敏感度特征的码率选择算法,在客户端利用人眼对比敏感度模型计算当前观看条件下人眼截止空间频率,选择服务器中和截止空间频率差的绝对值最小视频分片对应的码率作为目标码率。和基于带宽估算选择目标码率的方法进行对比实验,测试二者在不同视角内计算的目标码率,得到两者的码率计算结果阶梯图。实验结果表明,在视角为5o到15o情况下,所提方法较带宽估计方法在确保视频效果前提下能够有效节约带宽。

One significant advantage of rate selection algorithms based on bandwidth estimation is the high bandwidth utilization rate. They are, however, vulnerable to network bandwidth fluctuations, leading to appearance of rate instantaneous peak value and hence wasting unnecessary bandwidth consumption. To tackle the problem above, this paper proposes a novel rate selection algorithm based on the contrast sensitivity of human eyes where in the client eyes cutoff spatial frequency under the current viewing conditions is calculated by using the human contrast sensitivity model. The algorithm selects the rate of video fragment which has the minimum absolute difference value to the spatial frequency computed, stored in server as the target rate. Compared with those methods for calculating the target rate based on bandwidth estimation and testing target rate in different angles, the proposed method gets the ladder diagrams of rate calculation of both methods. Experimental results demonstrate that the proposed algorithm is able to save a considerable amount of bandwidth without the loss of video quality, with viewing angle from 5° to 15°.