Semantic transcoding of video based on regions of interest

Traditional transcoding on multimedia has been performed from the perspectives of user terminal capabilities such as display sizes and decoding processing power, and network resources such as available network bandwidth and quality of services (QoS) etc. The adaptation (or transcoding) of multimedia contents to given such constraints has been made by frame dropping and resizing of audiovisual, as well as reduction of SNR (Signal-to-Noise Ratio) values by saving the resulting bitrates. Not only such traditional transcoding is performed from the perspective of user's environment, but also we incorporate a method of semantic transcoding of audiovisual based on region of interest (ROI) from user's perspective. Users can designate their interested parts in images or video so that the corresponding video contents can be adapted focused on the user's ROI. We incorporate the MPEG-21 DIA (Digital Item Adaptation) framework in which such semantic information of the user's ROI is represented and delivered to the content provider side as XDI (context digital item). Representation schema of our semantic information of the user's ROI has been adopted in MPEG-21 DIA Adaptation Model. In this paper, we present the usage of semantic information of user's ROI for transcoding and show our system implementation with experimental results.