  Streaming erasure codes encode a source stream to guarantee that each source
packet is recovered within a fixed delay at the receiver over a burst-erasure
channel. This paper introduces diversity embedded streaming erasure codes
(DE-SCo), that provide a flexible tradeoff between the channel quality and
receiver delay. When the channel conditions are good, the source stream is
recovered with a low delay, whereas when the channel conditions are poor the
source stream is still recovered, albeit with a larger delay. Information
theoretic analysis of the underlying burst-erasure broadcast channel reveals
that DE-SCo achieve the minimum possible delay for the weaker user, without
sacrificing the performance of the stronger user. A larger class of multicast
streaming erasure codes (MU-SCo) that achieve optimal tradeoff between rate,
delay and erasure-burst length is also constructed.
