Active applications can add value to communication. Yet it involves sophisticated domain knowledge and complex development process. In this paper we discuss a framework for the construction of complex active network applications. Its design motivation is to enable an expert to develop complex active applications as a value added communication service and make it available for repeated use by the end-applications. As a test case we select a self-organizing adaptive video transcoding channel. This multi-component multi-tier novel active application enables video to propagate over extreme network with highly asymmetric link and node capacity. At the same time it offers a unified channel abstraction to its service subscriber. In this paper we focus how this channel abstraction can be composed within the proposed active service composition framework.