MediaStoreMediaExpired

A player following the live edge came to media the store had already expired: a recorder that keeps only so much (expiry by duration or size), under a player paused, slowed or started further behind than that. Rather than end, playback skips forward to media the store still has, its output timeline running on unbroken, and plays that much less far behind the recording. It skips to the start of the second-oldest chunk file each stream has, not the oldest, which is the next to go: a player at normal speed from there would come to each file as it expired. A player whose last cut does not follow the live edge ends with an error instead.