Fine-Grained Rate Shaping for Video Streaming over Wireless Networks
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Fine-Grained Rate Shaping for Video Streaming over Wireless Networks Trista Pei-chun Chen NVIDIA Corporation, Santa Clara, CA 95050, USA Email: [email protected]
Tsuhan Chen Department of Electrical and Computer Engineering, Carnegie Mellon University, Pittsburgh, PA 15213-3890, USA Email: [email protected] Received 30 November 2002; Revised 14 October 2003 Video streaming over wireless networks faces challenges of time-varying packet loss rate and fluctuating bandwidth. In this paper, we focus on streaming precoded video that is both source and channel coded. Dynamic rate shaping has been proposed to “shape” the precompressed video to adapt to the fluctuating bandwidth. In our earlier work, rate shaping was extended to shape the channel coded precompressed video, and to take into account the time-varying packet loss rate as well as the fluctuating bandwidth of the wireless networks. However, prior work on rate shaping can only adjust the rate coarsely. In this paper, we propose “fine-grained rate shaping (FGRS)” to allow for bandwidth adaptation over a wide range of bandwidth and packet loss rate in fine granularities. The video is precoded with fine granularity scalability (FGS) followed by channel coding. Utilizing the fine granularity property of FGS and channel coding, FGRS selectively drops part of the precoded video and still yields decodable bitstream at the decoder. Moreover, FGRS optimizes video streaming rather than achieves heuristic objectives as conventional methods. A two-stage ratedistortion (RD) optimization algorithm is proposed for FGRS. Promising results of FGRS are shown. Keywords and phrases: fine-grained rate shaping, rate shaping, fine granularity scalability, rate-distortion optimization, video streaming.
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INTRODUCTION
Due to the rapid growth of wireless communication, video over wireless network has gained a lot of attention [1, 2, 3]. However, wireless network is hostile for video streaming because of its time-varying error rate and fluctuating bandwidth. Wireless communication often suffers from multipath fading, intersymbol interference, and additive white Gaussian noise, and so forth; thus, the error rate varies over time. In addition, the bandwidth of the wireless network is also time varying. Therefore, it is important for a video streaming system to address these issues. Joint source-channel coding (JSCC) techniques [4, 5] are often applied to achieve error-resilient video transport with online coding. Given the bandwidth requirement, the joint source-channel coder seeks the best allocation of bits for the source and channel coders by varying the coding parameters. However, JSCC techniques are not suitable for streaming precoded video. The precoded video is both source and channel coded prior to transmission. The network conditions are not known at the time of coding. “Rate shaping,” which was
called dynamic rate shaping (DRS) in [6, 7, 8], was proposed to solve the bandwidth adaptation problem. DRS “shapes,” that is, reduces the bit rate of the single-layered pre source coded (pre-
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