Video coding techniques, widely used in videoconferencing and streaming applications over the Internet, may face degradation in performance when traversing satellite channels. The aim of the present paper is to provide objective measurements of the quality of video encoded sequences for two of the most popular video coders in this setting (namely, H.261 and MPEG-2), after transmission over faded satellite channels. In particular, the emphasis is on the Ka band, which is becoming an attractive alternative for commercial applications, but is more prone to quality degradation than the currently widely used Ku band. In order to test the behaviour of the coders in repeatable experimental conditions and over different data link platforms, two transmission chains have been implemented in the laboratory, by careful emulation of the required environment. The data link layer has been based on HDLC-like and DVB protocols, respectively. The experiments have been performed in the presence of additive white Gaussian noise (AWGN), and by using fading patterns derived by real world data. The results obtained highlight some often neglected aspects in the behaviour of the coders under examination, both in relation to their comparative performance and to their adaptability to different underlying data link protocols.
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