engleski

Quality of Service Control in Variable Bit Rate Video Communications

This paper first discusses the background of integration of video services in broadband integrated services digital network (B-ISDN). Various types of video services in B-ISDN ranging from videophone to high definition television (HDTV) should be supported by different end-to-end quality of service (QOS) levels. End-to-end QOS is recognized as a function of terminal capability, e.g. coding bit rate, and networks performance. Flexibility of QOS is achieved by adopting asynchronous transfer mode (ATM) technology. Thanks to variable bit rate (VBR) communications, realized by ATM, the terminal could generate its coded data at any bit rate. This means that terminals will be able to demand any QOS they wish. The QOS for video communication depends on the subjective assessment of viewers and indicates grade of quality perceived by viewers. To analyze the improvement in picture quality that is expected from variable bit rate coding, subjective evaluation of picture quality was performed. We choose coding bit rate as a parameter of terminal capability. From experiments, a relationship between coding bit rate and grade of quality was obtained.

video communications; ATM networking; variable bit rate coding; quality of service; image quality assessment

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