Why should someone you’ve never met decide what you can watch on TV and when you can watch it? True, there’s always a choice of channels, but the selection is still quite limited and unless you record programs in advance, you can only watch them when they’re broadcast. Wouldn’t it be better if watching TV were more like browsing the Web so you could pick the program you wanted to watch whenever and wherever you felt like watching it? That’s one of the promises of IPTV (Internet Protocol Television), which uses Internet technology to deliver TV programs “on demand.” How does it work? What benefits will it bring us? What challenges will the broadcasters and telephone companies face delivering these new services? Let’s take a closer look!
What is IP TV
From a TV watcher’s point of view, IPTV is very simple: instead of receiving TV programs as broadcast signals that enter your home from a rooftop antenna, satellite dish, or fiber-optic cable, you get them streamed (downloaded and played almost simultaneously) through your Internet connection. Not the kind of connection you have today, which can probably handle only 1–10 Mbps (million bits per second—roughly the amount of information in an average novel entering your computer every second!), but a broadband line with about 10 times higher bandwidth (information carrying capacity) of maybe 10–100Mbps. You watch the program either on your computer or with a set-top box (a kind of adapter that fits between your Internet connection and your existing television receiver, decoding incoming signals so your TV can display Internet programs).
From the viewpoint of a broadcaster or telephone company, IPTV is somewhat more complex. You need a sophisticated storage system for all the videos you want to make available and a web-style interface that allows people to select the programs they want. Once a viewer has selected a program, you need to be able to encode the video file in a suitable format for streaming, encryptit (encoding it so only people who’ve paid can decode and receive it), embed advertisements (especially if the program is free), and stream it across the Internet to anything from one person to (potentially) thousands or millions of people at a time. Furthermore, you have to figure out how to do this to provide a consistently high-quality picture (especially if you’re delivering advertising with your programming—because that’s what your paying advertisers will certainly expect).
Live programs are streamed as they’re produced, but prerecorded programs and movies need to be stored in such a way that they can be selected and streamed on demand. Some VOD services limit the number of programs they make available not because they’re short of storage space but because that’s one way to limit the overall bandwidth of their service and its impact on the Internet. (For example, if the BBC made available every program it’s ever produced on its iPlayer, which is free to use, a significant proportion of the entire UK Internet bandwidth would be taken up streaming TV soap operas and sitcoms, potentially slowing down the network for every other kind of Net traffic.)
First, the TV program (either prerecorded or captured live with a video camera) has to be converted into a digital format that can be delivered as packets using the Internet protocol. Sometimes the original program will be in digital format already; sometimes it will be in the form of a standard, analog TV picture (known as SD format) that needs an extra bit of processing (analog-to-digital conversion) to turn it into digital format. With current limitations on bandwidth, videos also need to be compressed (made into smaller files) so they can stream smoothly without buffering (periodic delays caused as the receiver builds up incoming packets). In practice, this means programs are encoded in either MPEG2 or MPEG4 format (MPEG4 is a newer form of video compression that gives higher quality for a similar bandwidth and requires only half as much bandwidth for carrying an SD picture as MPEG2). Once that’s done, advertisements have to be inserted, and the information has to be encrypted.