[opendtv] Re: IPTV on AP: Interactive TV Poised for a Rollout (Feb 13)
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: "OpenDTV (E-mail)" <opendtv@xxxxxxxxxxxxx>
- Date: Tue, 15 Feb 2005 13:01:42 -0500
John McClenny wrote:
> Everything that would be broadcast in a cable
> system is multicast in an IPTV system. One channel
> -- one stream. Only in the VOD case is there
> unicast.
Yes, of course. But I was responding to this comment:
> > An IPTV network can offer unlimited channels.
> > Then again, the same is true for a cable system,
> > if it is based on the routing of services, INSTEAD
> > of broadcasting them to everyone.
That comment shows a misunderstanding of IPTV and the
lack of consideration of basic system constraints.
The "instead of broadcasting," in this context, is
unicasting. He's talking about individual streams.
Any subscriber can download any content available
over the Internet.
The truth is, the multicasts in IPTV are analogous to
broadcasts in cable systems. And, as we already
discussed, must operate within a "walled garden." I
even pointed to an Internet Draft that addresses the
general multicast issues over IPv4 and v6. So in
practice IPTV and digital cable are not all that
different. And by the way, any subscriber of either
scheme can go and fetch video content over the
Internet. So even that is no different.
> The core bandwidth of the IPTV networks is pretty
> large - only at the edge are their constraints, and
> then only if DSL is used. The vastmajority of
> comsumers won't be effected by the bandwidth
> limitations.
So how is this different from cable networks? They too
are fiber optic and very wide in the core. But because
they deploy coax into homes, rather than Cat5e, they
have far more bandwidth at the edge.
My point was that the reason to go IPTV for telcos
is nothing like what the hype-meisters keep pretending.
The reason is that narrower local loop requires the
functionality of a typical cable STB to be located
upstream. That's it. The letters "IP" don't in
practice offer much more than that, compared with
what existing digital cable can offer.
> The IPTV people also have the late mover advantage -
> they can easily adopt new codecs and higher
> performance STBs as their base level of architecture
> without the cost of replacing an existing equipment
> base.
Sure. Then again, they *have* to use new codecs to be
competitive, with their narrow edge connections. And
cable systems have proven to be perfectly willing to
undertake costly upgrades, when there's a reason to do
so. A new AVC-enabled cable STB will cost no more for
a cable system than it would for an IPTV system.
There is one advantage to IPTV connections. *If* one
is not watching any TV, the IP pipe can be wider than
what many cable broadband systems might provide today.
But again, that is only a matter of adjustment and
tradeoffs. And not to forget that the core network
will only support so many really really fast
subscriber downloads at a time regardless.
Bert
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