一种基于HTTP自适应流的混合码率自适应算法

doi:10.11896/j.issn.1002-137X.2017.02.019

摘要/Abstract

摘要： 码率自适应算法是HTTP自适应流技术的热点和难点。提出一种综合网络带宽和缓存两个因素的终端码率自适应算法(Combined with Bandwidth and Buffer,CBB)。该算法采用“探测”的机制在应用层上估算网络实时带宽,避免视频码率频繁切换；然后构建随缓存状态动态变化的平滑因子模型,并基于指数加权移动平均(EWMA)实现带宽的平滑处理；利用推动缓存趋近均衡级别变化的调度策略,尽可能使缓存区的数据量处于均衡的范围。整个算法经带宽估算、平滑处理、量化及确定调度时间构成一个循环作用的闭环。在使用MPEG-DASH标准的参考平台libdash上验证该算法的性能,结果表明,在变化的网络状况中所提算法表现良好。

关键词: HTTP自适应流,码率控制,网络带宽,缓存状态,MPEG-DASH

Abstract: The rate-adaptation algorithm is the hotspot and difficulty in adaptive HTTP streaming(AHS).In this paper,we proposed a hybrid rate-adaptation algorithm (Combined with Bandwidth and Buffer,CBB) for adaptive HTTP streaming.It is designed at the application layer using a “probe” principle to estimate the real-time bandwidth and avoid frequent switching of video rate.Then an exponential weighted moving average smoother (EWMA) is applied in bandwidth smoothing procedure.The smoothing factor can vary with the client buffer status to reduce buffer overflows.The schedule strategy is designed to keep buffer level in a balanced range as far as possible.The whole algorithm includes estimating,smoothing,quantizing and scheduling.These four steps proceed to form a circular closed-loop.The algorithm has been verified on the MPEG-DASH standard reference platform-libdash,and the experiments show that our algorithm performs well under varying network conditions.

Key words: AHS,Rate control,Network bandwidth,Buffer state,MPEG-DASH

熊丽荣,雷静之,金鑫. 一种基于HTTP自适应流的混合码率自适应算法[J]. 计算机科学, 2017, 44(2): 129-134. https://doi.org/10.11896/j.issn.1002-137X.2017.02.019

XIONG Li-rong, LEI Jing-zhi and JIN Xin. Hybrid Rate Adaptation Algorithm for Adaptive HTTP Streaming[J]. Computer Science, 2017, 44(2): 129-134. https://doi.org/10.11896/j.issn.1002-137X.2017.02.019

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