Mobile based collaboration such as image tagging and video annotation has become a hot research for both academic research groups and the industry. Current mobile platforms such as Google's Android and Apples's iOS have almost the same computing and multimedia capabilities as modern computers. This makes it possible for their users conduct regular collaborative activities as described before. Moreover their embedded geographic sensors can provide useful auxiliary metadata to help improve the

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... uracy of several collaboration features such as location annotation and tagging recommendation. In this paper, we firstly analyze most recent research on mobile based collaboration and annotation on digital contents, and then we introduce our efforts in expanding our collaborative annotation framework to the mobile platforms, especially the android-enabled devices. A prototype of the mobile extension that supports collaborative annotation on real time data streams especially audiovisual streams is introduced as well as several preliminary performance experiments.