Defining a multimedia remote viewer for mobile thin clients comes across with threefold scientific/technical constraints: (1) providing at the client side heterogeneous multimedia content and the support for ultimate collaboration functionalities, (2) ensuring a stable quality of services despite constrained resources available for the network and the terminal, and (3) featuring terminal independency and benefiting from community support.The present thesis addresses these challenges by developing a collaborative, semantic multimedia remote viewer. The underlying architecture features novel components for scene-graph creation and management, as well as for collaborative user events handling.The adaptive compression of the multimedia scene graph and the lossless compression of the collaborative messages are optimized through two devoted algorithms. The former creates a unique scene-graph, intrinsically adaptable to the network/terminal conditions. The latter dynamically generates and updates the encoding table according to the messages generated by the collaborative users. Both algorithms are patented.The direct collaborative functionality is ensured at the content level by enriching the scene graph with a new type of node where currently becomes a part of the ISO standards.The experimental setup considers the Linux X windows system and BiFS/LASeR multimedia scene technologies on the server and client sides, respectively. The implemented solution was objectively benchmarked against currently deployed solutions (VNC RFB and Microsoft RDP), by considering text-editing and www-browsing applications. The quantitative assessments demonstrate: (1) limited depreciation of the visual quality, e.g. PSNR values between 30 and 42dB or SSIM values larger than 0.9999; (2) downlink bandwidth gain factors ranging from 2 to 60; (3) efficient real-time user event management expressed by network roundtrip-time reduction by factors of 4 to 6 and by up-link bandwidth gain factors from 3 to 10; (4) feasible CPU activity, larger than in the Microsoft RDP case but reduced by a factor of 1.5 with respect to the VNC RFB.
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