Active routers allow computation to be performed within the network by processing packets when they pass through the routers. We design and implement a cluster-based active router system that provides multimedia stream transcoding service. The performance of the system is evaluated with three different load balancing schemes. We evaluate the out-of-order phenomenon and analyze the tradeoff between this phenomenon and the processing speed. We present a stream-based round robin algorithm for the transcoding service offered in the router and demonstrate its superiority over the conventional round-robin scheme. The main design criteria are to minimize the total transcoding time and maintain the order of media units for each outgoing stream.