This paper describes a system architecture, which enables the automatic semantic annotation and adaptation of multimedia content in context-aware content sharing environments. The discussed architecture is the result of research done in the EU FP6 IST INTERMEDIA project. Generating a common vision on user-centric multimedia services in shared content environments to provide users with content personalized to their user preferences and usage environment is one of the objectives of the project. The work presented in this paper describes how media formats with their related metadata are automatically annotated and dynamically adapted. Based on the architecture, a full-featured demonstrator is built. Keywords Semantic annotation and adaptation