Seamless Bit-Stream Switching in Multirate-Based Video Streaming Systems
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Seamless Bit-Stream Switching in Multirate-Based Video Streaming Systems Wei Zhang and Bing Zeng Department of Electrical and Electronic Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong Received 15 August 2005; Revised 18 December 2005; Accepted 15 March 2006 This paper presents an efficient switching method among non-scalable bit-streams in a multirate-based video streaming system. This method not only takes advantage of the high coding efficiency of non-scalable coding schemes (compared with scalable ones), but also allows a high flexibility in streaming services to accommodate the heterogeneity of real-world networks. One unique feature of our method is that, at every preselected switching point, the reconstructed frame at each rate or two reconstructed frames at different rates will go through an independent or a joint processing in the wavelet domain, using an SPIHT-type coding algorithm. Another important step in our method is that we will apply a novel bit allocation strategy over all hierarchical trees that are generated after the wavelet decomposition so as to achieve a significantly improved coding quality. Compared with other existing methods, our method can achieve the seamless switching at each preselected switching point with a better rate-distortion performance. Copyright © 2006 Hindawi Publishing Corporation. All rights reserved.
1.
INTRODUCTION
Due to the rapid growth and wide coverage of the Internet in recent years, there is a great increase of demand on various video services over the Internet, especially the real-time video streaming service. In contrast with the download mode where a video session is downloaded entirely to a user before it can be played, real-time video streaming enables users to enjoy the video service right after a very small portion of the whole video session is received. However, the Internet is an inherently heterogeneous and dynamic network, that is, the connecting bandwidth between the server and each user is varying with time. Under such circumstance of varying bandwidth, how to maintain a robust quality of service (QoS) is perhaps the most challenging requirement during each service session. In response to this challenge, two different source coding approaches have been developed in recent years, which are briefly outlined in the following. 1.1. Multirate non-scalable coding scheme versus scalable coding scheme One straightforward solution to the challenge mentioned above is to perform a multiple bit-rate (MBR) representation, that is, to encode each source video into multiple nonscalable bit-streams, each at a preselected bit-rate. At each
time-slot during the streaming service, an appropriate bitstream is selected according to the available bandwidth and then transmitted to the user. Clearly, each bit-stream generated here can be encoded optimally at the chosen bit-rate. On the other hand, however, it is also clear that we cannot make the best use of the available bandwidth when it is between two preselected rates. In
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