The Rewind Subscription Filter

This document proposes a Media Over Quic Transport (MOQT) extension that enables a new Subscription Filter, so that a subscriber can request that a finite number of past groups be delivered with SUBSCRIBE semantics (multiple streams, potentially incomplete) rather than FETCH semantics (single stream, complete, head-of-line- blocking). Service of this request is best-effort by the publisher, and it intended to accelerate joining a track in some use cases.