Browsing by Author "Zhang, YQ"

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On end-to-end architecture for transporting MPEG-4 video over the Internet
(2000-09-01)
Wu, DP
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Hou, YWT
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Zhu, WW
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Lee, HJ
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Chiang, TH
With the success of the Internet and flexibility of MPEG-4, transporting MPEG-4 video over the Internet is expected to be an important component of many multimedia applications in the near future. Video applications typically have delay and loss requirements, which cannot be adequately supported by the current Internet, Thus, it is a challenging problem to design an efficient MPEG-4 video delivery system that can maximize the perceptual quality while achieving high resource utilization. This paper addresses this problem by presenting an end-to-end architecture for transporting MPEG-4 video over the Internet, We present a framework for transporting MPEG-4 video, which includes source rate adaptation, packetization, feedback control, and error control. The main contributions of this paper are: 1) a feedback control algorithm based on Real Time Protocol (RTP) and Real Time Control Protocol (RTCP); 2) an adaptive source-encoding algorithm for MPEG-4 video which is able to adjust the output rate of MPEG-4 video to the desired rate; and 3) an efficient and robust packetization algorithm for MPEG video bit-streams at the sync layer for Internet transport. Simulation results show that our end-to-end transport architecture achieves good perceptual picture quality for MPEG-4 video under low bit-rate and varying network conditions and efficiently utilizes network resources.
Online rate control for video streams
(2001-05-01)
Pejhan, S
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Chiang, TH
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Zhang, YQ
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
A mechanism for varying the frame rate of pre-encoded video clips online is described. The mechanism relies on two different encoders. An offline encoder creates a high-quality bit stream encoded at 30 fps, as well as separate files containing motion vectors for the same clip at lower frame rates. An online encoder decodes the bit stream (if necessary) and re-encodes it at lower frame rates in real time using the precomputed, stored motion information. Online frame rate control, used in conjunction with dynamic bit rate control, allows clients to solve the rate mismatch between the bandwidth available to them and the bit rate of the pre-encoded bit stream. Clients can therefore choose the amount of trade-off between temporal and spatial quality while resolving the rate mismatch problem. Moreover, online frame rate control provides a natural means for implementing a VCR-like fast forward control for video streaming applications, without increasing bandwidth consumption.
Scalable rate control for MPEG-4 video
(2000-09-01)
Lee, HJ
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Chiang, T
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Zhang, YQ
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交大名義發表
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National Chiao Tung University
This paper presents a scalable rate control (SRC) scheme based on a more accurate second-order rate-distortion model. A sliding-window method for data selection is used to mitigate the impact of a scene change. The data points for updating a model are adaptively selected such that the statistical behavior is improved. For video object (VO) shape coding, we use an adaptive threshold method to remove shape-coding artifacts for MPEC-4 applications. A dynamic bit allocation among VOs is implemented according to the coding complexities for each VO, SRC achieves more accurate bit allocation with low latency and limited buffer size. In a single framework, SRC offers multiple layers of controls for objects, frames, and macroblocks (MBs), At MB level, SRC provides finer bit rate and buffer control. At multiple VO level, SRC offers superior VO presentation for multimedia applications. The proposed SRC scheme has been adopted as part of the International Standard of the emerging ISO MPEG-I standard [1], [2].