On Mon, 12 Feb 2007, Peter Beckman wrote:
NBC can now stream their shows to me as a .mp4 and I could grab them as fast as they could send it, rather than in realtime. They might offer the same stream at different data rates: 1mbps, 5mbps, 10mbps, 30mbps (for those of us lucky enough to have Verizon FIOS at home). The streams would simply repeat once they streamed all the files in a list.
That is what layered IPmc is. There is a base stream and on top of that additional "layers" are interleaved and you pick up just what you need - depending on your b/w. There are other facets to layered IPmc such as staggered streams, whereby the same VOD is transmitted 10x an hour, at 6 minute intervals and using clever encoding you "tap" into the multicast stream and within an average of 3 minutes your VOD starts playing - at the level of quality based on your available b/w.
I've seen this in action as far back as 1998 and just don't quite grok why it never took off.
-Hank