双重控制策略在流媒体连续播放中的应用

传统的发送速率控制和播放速率控制由于各自的局限性,很难克服网络时延扰动对流媒体连续播放的影响.为了改善播放系统的性能,将双重控制策略应用到流媒体播放中,在发送端发送速率控制采用了内模控制器以克服传输延迟的影响,在接收端播放速率控制采用了简单的PID控制器,两种控制共同调节缓冲区长度.实验表明该方法能够处理传输时延和网络扰动引起的失步对播放的影响,缓冲区长度能够稳定在合理的区间,有效地防止缓冲区下溢造成的播放停顿以及缓冲区上溢造成的播放跳跃.发送速率变化率较小,有利于避免网络拥塞的发生.尤其是在网络出现大的扰动时,与其他方法相比,控制效果更加理想,播放更加流畅.

Application of dual-mode control in the continuous playback of streaming media

Because of the limitations in the traditional sending-rate control and the play-rate control, it is difficult to eliminate the delay and the influence of network disturbances in the continuous playback of streaming media. To improvethe performance of the play system, a dual- mode control is applied. An internal mode feedback control of the sending-rate in the source is adopted to overcome the adverse effect caused by the propagation delay; and a simple PID controller of playback-rate in the sink is adopted to control the buffer length of the sink. Experiments show that this scheme reduces the influence of asynchronization caused by the delays in transmission and the disturbances of network in playback, and clamps buffer length at a steady value around the target buffer occupancy, effectively preventing the play-pause in buffer underflow and the play-jump in buffer overflow. The variation of the sending-rate is reduced, which is helpful to reduce the network congestion. Compared with the existing methods, it exhibits better control performances in the continuous playback under large network disturbances.