Conference Paper

Optimal Frame Selection with Adaptive Playout for Delivering Stored Video under Constrained Resources

Nanyang Technol. Univ., Singapore
DOI: 10.1109/ICME.2007.4285021 Conference: Multimedia and Expo, 2007 IEEE International Conference on
Source: IEEE Xplore

ABSTRACT In this paper, we propose a server-client coordinated joint optimal frame selection with adaptive playout for delivering stored video under both limited channel bandwidth and finite client buffer condition. In particular, the client will reduce the frame playout rate whenever its buffer fullness level falls below a given threshold in an attempt to prevent buffer underflow. And when the buffer fullness exceeds the threshold, the client will switch back to the normal frame playout rate. The server is aware of the adaptive playout decision made by the client and incorporates the decision into its optimal frame selection framework for joint optimization. The objective is to minimize the number of frames that must be discarded in order to prevent client buffer underflow or overflow and make full use of the limited bandwidth resource.

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    ABSTRACT: Recently smooth adaptive media playout (SAMP) was suggested to deal with the visual quality degradation problem caused by the fluctuation of playout speed in conventional AMP. However, while encountering the burst packet losses, it still had a potential buffer outage risk if buffer level was not safe enough. In this paper, a safety guaranteed SAMP (SG SAMP) algorithm is proposed to deal with the above hazard. Whenever the current buffer level deviates from the predefined safe area, the linear playout adjustment order is triggered to maintain the buffer safety. The simulation results have shown that SG SAMP outperforms SAMP in reducing the buffer outage probability and provides smooth and reliable playback, especially in wireless video streaming. The playout adjustment number and the frame loss number are both about 30% less.
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    ABSTRACT: This paper aims to reduce the amount of prebuffering required to ensure a maximum video continuity in streaming. Current approaches do this by slowing the playout frame rate of the decoder, this is known as adaptive media playout (AMP). However, doing this introduces playout distortion to the viewers as the video is played slower than its natural playout rate. We approach this by proposing a frame rate control scheme that jointly adjusts the encoder frame generation rate of the encoder and the playout frame rate of the decoder. In addition to using AMP to improve video continuity, we also allow the encoder to increase the encoder frame generation rate. This means the encoder will be sending more frames to the decoder to quickly increase the number of frames available at the playback buffer, thus lowering the chance of buffer underflow which causes discontinuity in video playback. At the same time, the increase in the number of frames at the playback buffer may mean that the decoder does not need to use AMP to delay the playback, thus lowering the playback distortion. However, the increase in encoder frame generation rate comes at a price because frame quality will need to decrease in order to meet the constraint on available network bandwidth. This implies that the scheme needs to find the optimal trade-off between frame quality, playout distortion and video continuity. To do that, we characterize the frame rate control problem using Lyapunov optimization. We then systematically derive the optimization policies. We also show that these policies can be decoupled into separate encoder and decoder optimization policies, thus allowing for a distributed implementation. Simulation results show significant reductions in the prebuffering requirements over a scheme that perform no frame rate control and lower playout distortions compared to the AMP schemes, while exhibiting a modest drop in frame quality.
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