1. A system comprising: one or more stream sources configured to generate a plurality of input streams containing a given content at a plurality of bitrates, a plurality of resolutions, or a plurality of bitrates and resolutions; and a stream controller configured to generate a plurality of output streams in response to the plurality of input streams, wherein said stream controller is further configured to (i) determine when one of the plurality of input streams becomes invalid, (ii) switch generation of an output stream associated with the invalid input stream from the invalid input stream to a valid one of the plurality of input streams, and (iii) when the invalid input stream becomes valid again, switch the generation of the output stream back to the now valid input stream.