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Word (8 KB)Syntax and Semantics of Control Messages for User Interaction
Summary
Interactivity is very prominently placed in current MPEG-4 activity. Even though a back channel is specified to support interactivity, the syntax and semantics for such interaction messages is not specified. Existing standards such as DSM-CC and RTSP support traditional VCR-type interactivity to reposition a media stream during playback. These existing specifications are not adequate, as MPEG-4 applications potentially require complex interactive control beyond the VCR-type control offered by these models. The concept of generic, CGI-like application-specific interactive messages was proposed in our earlier contribution (MPEG97/M2888) to the 41st MPEG meeting. In this contribution, we detail the syntax and semantics for the control messages for user interaction exchanged between clients and servers (the terms clients and servers are functional notations and can represent clients and servers depending on their functionality and connectivity).