IP Multicast as a solution to video distribution is a non-starter. IP
Multicast for the wide area is a failure. It assumes large numbers of
people will watch the same content at the same time.
They do.
Sure it degrades to effective unicast if too few people watch the same
channel in the same area (so just use unicast for those channels), that
doesn't mean it's no use for the popular channels that have millions of
viewers.
The usage model
that could work for it most mimics the broadcast environment before
cable TV, when there were anywhere from three to ten channels to
choose from, and everyone watched one of those. That model has not
made sense in a long time. The proponents of IP Multicast seem to
have failed to notice this.
10 or 1000 channels it's going to be better than not using it. I don't
see the logic in using it for nothing because it's not good for some
things.
There are local factors that may mean some countries adopt it. In the
UK all spectrum is sold, as we turn off analog it's not a given that
the broadcasters will be able to buy that spectrum for HD. When we want
10 HD Olympics channels IPTV may be the only way for a large portion of
the 20M or so viewers to get it.
The point is the more
possible live content there is, the less multicast makes sense.
Compounding this, fewer people care to watch live content, preferring
instead to record and watch later on their own schedule, or be served
on-demand. In this usage model, multicast is not helpful either.
Because they want to watch later doesn't make multicast no use.
Who is going to pay for their time shift bandwidth use? Why would
someone pay when a home device can do the time shift and make good use
of the live multicast stream? They'll save the download cash for stuff
that never was available live to them or they forgot to record, unless
someone makes it appear to have no cost.
brandon