The rollout of ADSL2+ in the UK appears to be going through a reverse-hype process, with people saying it’s not going to deliver high speeds to most people. That may be partially true, but in urban areas where people are within 1.5Km of the exchange they should get 20Mb/s+.
These speeds are enough for multi-channel HDTV. At the extreme end (extremely optimistic end?), we’ve seen Microsoft demonstrate what they call near-HDTV running at 1.5Mbps. A more ‘normal’ size for HD will be running at 2.5-4Mbps.
We can see that the delivery to the home isn’t a problem, but the back-haul (speaking between the exchange and the content provider) is another matter. Unless intelligent delivery and caching is used, shipping that amount of content to all of your customers gets very expensive.
Most people do seem to be ignoring QoS though, as having 20Mb/s downstream and 1.3Mb/s upstream is still useless for VoIP unless some of that bandwidth can be guaranteed so the voice traffic doesn’t get mixed in with everything else.
Using traditional CoDecs and then packetising them uses more bandwidth than over traditional telephony links. VoIP bandwidth can be squeezed to much lower levels, but then the calls are not what’s called toll-grade.
Broadband providers moving into VoIP are going to need to look long and hard how they actually implement services such that they are competitive (in terms of call quality) with existing analogue lines.