Decision engine for dynamically selecting media streams

An online system receives content (e.g. video content and/or audio content) from a content provider device to be appropriately transcoded and distributed to client devices for consumption. During the transcoding process, the online system decodes the content into an intermediate format, and. considers a variety of characteristics to decide the optimal set of content encodings for encoding the decoded content. Characteristics include source characteristics associated with the content provider device, social graph characteristics of the user of the online system that is using the content provider device, viewer characteristics associated with the client devices that request to access the content, and content characteristics. The online system encodes the content for each client device with appropriate encoders selected based on the optimal set of content encodings. For each client device that requests to access the content, the online system provides encoded content that the client device can appropriately playback.