A controller may preview media streams from a plurality of source devices, and may select between the streams, add processing or additional content to the streams, and provide an edited or mixed stream to one or more client or recipient devices. In many implementations, mixing or selective presentation of streams may be accomplished with little to no delay via a lightweight signaling and chunk identification change protocol. In other implementations, processing and mixing instructions may be provided to client devices, which may retrieve the streams and process them locally, reducing or eliminating delay from an intermediary processor or mixer.