KEYWORDS: Video, Local area networks, Computer programming, Video compression, Relays, Control systems, Video coding, Data transmission, Software development, Network architectures
For video applications such as video-on-demand, signaling is an important step for service initialization including service setup, authentication, and resource allocation. This paper describes the design and implementation of an experimental platform for delivery of real-time MPEG encoded video over LAN with DSM-CC signaling. The platform consists of a real-time MPEG encoder system as a server, a network node workstation, and a client with MPEG decoding capability. Specifically, we have implemented a client- initiated subset of the DSM-CC user-to-network (UN) protocol for signaling. Communication between the network node and server/client is achieved by using the TCP/IP protocol. The network node provides the functionality of upstream message exchange, UN and/or UU (user-to-user) resource negotiation, and MPEG bitstream relay. The operation of our current video platform setup is quite robust and can deliver MPEG video up to about 1.5 Mb/s via DSM-CC protocols. It is demonstrated that practical implementation of video applications is feasible over small-scale LANs.
MPEG1 video coding standard is an international standard primarily aimed at storage applications, and has been adopted in 1992. As a second work item by the ISO MPEG committee, MPEG2 standard is being considered for broader applications. In this paper, we investigate the advantages of the more complicated MPEG2 standard over the MPEG1. An overview on the technology of the standards and their major differences is given. Simulation results are presented to compare the performance of the two standards in terms of quality, quantization, bit count, and buffer content. It is shown that the MPEG2 yields better performance especially for highly interlaced video sequence.
Motion vectors are side information vital to motion-compensated predictive/interpolative interframe video coding algorithms. This paper is concerned with the coding efficiency for this motion information. It is demonstrated that coding differential motion vectors is not always advantageous. An adaptive strategy is thus considered to automatically select the most favorable mode to code the motion information. The effects of video noise to motion estimation and coding are also investigated. A simple linear filtering scheme is used to reduce the noise effects. Simulation results show a significant performance improvement for noisy video by using this simple filtering scheme.
Discrete cosine transform (DCT) coding has been emerging as a key element for image data compression. Conventional DCT coding algorithms which treat all the image areas indiscriminately unfortunately give nonuniform image quality for various image contents. This motivates work on DCT schemes adaptive to the image contents so that a better tradeoff between bit rate and image quality can be achieved. In this paper a DCT algorithm with adaptive thresholding and quantization is combined with variable block size segmentation to further improve the coding performance. A new segmentation criterion is proposed. Some simulation results are given to illustrate the superiority of this adaptive DCT algorithm with segmented blocks. It is also shown that this algorithm poses itself as a promising compression method to deal with the composite images consisting of text/graphics and natural scenes.
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