The potential of the Internet as a broadcast platform

The Internet offers a huge amount of potential as a broadcast platform. To demonstrate why this is so is best demonstrated by comparing it with the Freeview platform. Freeview has been a great success so far, but the amount of bandwidth available on Freeview is extremely limited. By employing new technologies — the forthcoming DVB-T2 transmission standard and the MPEG-4 H.264 video codec — Freeview will be able to carry 3 or 4 HDTV channels UK-wide once digital switchover has been completed in 2012 (TV regions switching over early will be able to receive HDTV channels once the analogue TV signal has been switched off, though).

In comparison, Brandon Butterworth, the Principal Technologist in the BBC's R&D department (also the person who originally set up, and the person who suggested that the iPlayer TV service should use streaming rather than P2P downloading in the summer of 2007), has said that the BBC could deliver a dozen or more HDTV streams in parallel via the Internet when the London Olympics is on in 2012 — the same year in which digital switchover will be completed — with each stream covering a different sporting event.

The BBC wouldn't even be able to deliver a dozen HDTV channels in parallel via digital satellite, which a BBC engineer once described as being "God's own broadcasting system" due to the abundance and low cost of bandwidth on satellite. The BBC has a total capacity  of 231 Mbps on digital satellite, and a dozen HDTV channels using 8 Mbps each would require a little under half of that capacity alone, so the BBC would have to lease additional satellite transponders, which would be very expensive.

The technology that would allow the BBC to deliver a dozen HD streams via the Internet is called multicast, which is the key enabling technology for delivering live TV channels via the Internet. Multicast only requires that a broadcaster deliver one stream of each channel, and the 96 Mbps of bandwidth required to deliver a dozen 8 Mbps HDTV channels is a small amount of bandwidth in terms of the bandwidth that the website has to deal with, which will be of the tens of gigabits per second range — especially since the launch of the BBC iPlayer TV streams.


Ultra-high-definition TV (UHDTV)

Another example that demonstrates the massive potential that the Internet offers, but this time looking quite a few years into the future, is ultra-high-definition TV (UHDTV), which NHK (the Japanese equivalent of the BBC), has begun researching for some time. UHDTV, which is also known as Super Hi-Vision, will provide sixteen times the resolution of the 1080p HDTV format, because the picture will consist of four times as many pixels in both the horizontal and the vertical directions — 7,680 x 4,320 pixels as opposed to 1920 x 1080. The specifications for the audio are incredibly high as well, as it supports 22-speaker surround sound!

An uncompressed UHDTV signal has a bandwidth of 24 Gbps, which NHK has managed to compress down to 120 Mbps using the BBC's Diract video codec, and the audio has been compressed down to between 7 - 28 Mbps.

  • The total capacity on Freeview will be around 160 Mbps once digital switchover has been completed, so it's safe to say that we'll never see UHDTV channels with a bit rate of around 130 Mbps being transmitted on Freeview
  • Satellite transponders used to transmit broadcast TV typically have a capacity of about 30 - 40 Mbps, so a UHDTV channel would require multiple transponders to transmit the signal simultaneously, and consumer satellite dishes would likely need to use multiple LNBs (low noise blocks) and chips used in satellite set-top boxes would need to use multiple receivers. Delivery of UHDTV would therefore be expensive in terms of the bandwidth costs for the broadcasters, and satellite set-top boxes .

The introduction of UHDTV will likely lead to big changes to the TV broadcasting landscape, as it will lead to the eventual demise of terrestrial TV and, as it will be far cheaper to deliver UHDTV via broadband than via satellite, it's likely to lead to broadband eventually becoming the main broadcasting platform for TV.