by Chris Woodford. Last updated: January 23, 2017.
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!
Photo: The hugely popular British Broadcasting Corporation (BBC) iPlayer is an example of a type of IPTV known as video on demand (VOD). You can watch programs that have been broadcast on about a dozen different TV and radio channels in the last seven days (and occasionally for longer). It doesn't currently provide live broadcasts.
What is IPTV?
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, encrypt it (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).
Three types of IPTV
IPTV comes in three different flavors. The first
kind—and the one you're probably using already—is called video on
demand (VOD). With a service such as Netflix (an online movie website), you select a TV
program or movie you want to watch from a wide range, pay your money, and watch it there and then. A
different kind of IPTV is being offered by some of the world's more
enterprising TV broadcasters. In the UK, the BBC
(British Broadcasting Corporation) makes its last week's programs
available online using a web-based streaming video player called the
BBC iPlayer. This kind of service is sometimes called time-shifted IPTV,
because you're watching ordinary, scheduled broadcasts at a time that's convenient for you.
The third kind of IPTV involves broadcasting live TV
programs across the Internet as they're being watched—so it's live IPTV or
IP simulcasting. All three forms of IPTV can work either using your computer and an ordinary web
browser or (for much better quality) a set-top box and an ordinary digital TV. All three can be delivered
either over the public Internet or through a managed, private network that works in
essentially the same way (for example, from your telephone and Internet service provider
to your home entirely through the provider's network).
Photo: IPTV... without the TV! Here I'm watching pay-as-you-go, video on demand on a large HD smartphone (a "phablet" somewhere between a phone and a tablet) using Amazon's Instant Video (its answer to Netflix).
Personalized interactive TV
Traditional TV broadcasting means one-way,
one-to-many delivery of information, but combining television and
video pictures with the Internet opens up the possibility of a much
more interactive experience where information flows in both
directions. We're already used to TV talent shows where people phone
in to vote for their favorite acts, but in a future where TV programs
are delivered online, we can expect far greater involvement in the
programs we watch. Instead of TV presenters talking to a live
audience of a few hundred people in a studio, they'll be talking to a
live audience of thousands or millions of viewers who can send
instant feedback. We'll be able to ask questions and have the
presenter answer them minutes later! Or maybe we'll vote on how we
want TV soaps to play out, with multiple endings filmed in advance
and different ones screened to different viewers!
If you've used VOD services, you might have noticed that some of them are already delivering interactive advertising:
since you're essentially just viewing a video in an ordinary web page, you can click on an advertisement to go to a website and find out more. Given the trend toward highly targeted, online behavioral advertising, advertisers will use IPTV to deliver advertisements that are much more relevant to the individuals who watch them. That's
going to prove more effective and attractive for them than the catch-all, generic ads they screen today on today's broadcast TV channels,
not least because may people record programs for later viewing and fast-forward over the ads (something you can't do with IPTV). It's
very likely you'll even be able to choose the advertisements you want to watch ("Only show me ads about fashion/sport").
How does IPTV work?
With traditional TV, programs are broadcast by
being turned into radio waves and beamed through the air to a rooftop
antenna on your home. The antenna converts the waves back into
electrical signals and your TV set decodes them to make its
sound and picture (satellite TV works the same way, except the signal bounces into
space and back, while cable TV sends the signal directly into your home without radio waves). How is IPTV different?
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.
When you browse a website, you're effectively making a temporary link between two computers so one can "suck"
information off another. Your computer (the client) pulls
information off the other, typically much more powerful computer (the
server) by linking directly to an IP address that corresponds
to the website you want to look at. The client and server have a
brief, intermittent conversation in which the client requests from
the server all the files it needs to build the page you're looking
at. Servers are generally so fast and powerful that many clients can
download in this way simultaneously, with very little delay. This
kind of ordinary downloading between one client server and one server
is known as IP unicasting (most web browsing falls into this category).
When it comes to streaming (playing programs as you download them), however, the clients
put a much greater (and simultaneous) load on the server, which has the potential to cause unacceptable delays and buffering. So with
streaming, a different kind of downloading is used, known as IP
multicasting, in which each packet leaves the server only once but is sent simultaneously to many
different destinations; in theory, this means one server can send
information to many clients as easily as to a single client. So if
you have 1000 people all watching the World Cup final at the same
time over the Internet, they'd be receiving packets of streamed video
from a single server sent simultaneously to 1000 clients using IP
multicasting. If the same TV provider is simultaneously offering an
episode of Friends and some of the original 1000 people decide to
"switch channels" to watch it, effectively they switch over from
one IP multicast group to another and start receiving a different
The worldwide nature of the Internet makes it difficult to
send information equally as reliably from your server to a local
client as to a client on the opposite side of the planet. That's why
IPTV providers often use synchronized, worldwide networks on servers,
known as content delivery networks (CDNs), which keep "mirror"
copies of the same data; then people in the United States might
stream programs from Mountain View, California, while those in Europe
might get them from Frankfurt, Germany.
When you stream a program, you're not downloading it like an ordinary file. Instead,
you're downloading a bit of a file, playing it, and, while it's
playing, simultaneously downloading the next part of the file ready
to play in a moment or two. None of the file is stored for very long.
Streaming works because your computer (the client) and the computer it's receiving data
from (the server) have both agreed to do things like this. The Internet successfully links practically all the world's computers because they
all agree to talk to one another in the same way using prearranged technical procedures called protocols.
Instead of using the ordinary, standard, web-based protocols for
downloading (technically, they go by the names HTTP and FTP), streaming involves using protocols
adapted for simultaneous downloading and playing, such as RTP
(Real-Time Protocol) and RTSP (Real-Time
Streaming Protocol). Multicast streaming involves using IGMP
(IP Group Membership Protocol), which allows one server to broadcast to members of a group of
clients (effectively, lots of people all watching the same TV channel).
Making IPTV available over the public Internet is very different from delivering it over a private, managed network,
which is what many IPTV providers will ultimately elect to do: by controlling the entire network, they can guarantee
a level of quality and service. In practice, this means having a highly organized, hierarchical network with a national office
known as a super head-end (SHE, where programs are stored and the entire service is coordinated) feeding into
regional hubs called video hub offices (VHOs) that, in turn, service local distribution offices linked to set-top boxes in individual homes.
Everyone who has a computer and a broadband Internet connection can watch IPTV, but most
of us don't want to watch television on a crude laptop screen. That's
why the future of IPTV is likely to involve viewers buying set-top
boxes (sometimes called STBs) that receive input from your Internet
connection (either via an Ethernet cable or Wi-Fi), decode the
signal, and display a picture on your high-definition, widescreen TV.
STBs are effectively standalone computers programmed to do only one
thing: receive packets of streamed video, decrypt them, convert them
back to video files (MPEG2, MPEG4, or whatever format they were in
originally), and then display them as high-quality TV pictures.
Apple TV works broadly this way, using a set-top box to run
simple apps on a slimmed-down operating system (tvOS), which
manages the process of streaming video via the Internet.
Photo: A typical dongle. It turns your existing TV into a streaming device, connecting it to the Internet via Wi-Fi and HDMI.
As a simple, more compact, and much more discreet alternative to a set-top box, you can use what's called a dongle, which looks a bit like a USB flash-memory stick, but allows secure access to Internet TV programs.
The dongle plugs into an HDMI (high-speed, high-definition digital video) socket on your TV and connects via Wi-Fi to the Internet to stream TV programs, movies, and music directly. Some dongles are entirely self-sufficient: Roku and Amazon Fire work this way without any help from a computer or mobile device. Google's Chromecast is a little bit different: generally, you get it going with your computer, tablet, or smartphone (which effectively becomes a remote control), after which it directly streams your movie or TV program from the Internet.
What's the difference between a set-top-box and a dongle? It's pretty much this simple:
a set-top system is a bigger box that contains a faster processor with more memory, so it can give higher quality video output; that makes it better for things like high-performance gaming. Some companies, such as Amazon and Roku, offer a choice of either a simple, relatively expensive dongle or a more expensive, higher-spec set-top box.
The future of broadcasting?
There's no great clamor from ordinary TV viewers
for IPTV, although that's not unusual where new inventions and
innovations are concerned; no-one can truly appreciate something they
haven't yet experienced. But the huge popularity of VOD websites such
as BBC iPlayer and time-shifting personal video recorders (PVRs) such as TiVO (and Sky+
in the UK) strongly suggest TV will move increasingly away from
broadly defined channels and rigid schedules to more narrowly
focused, pay-per-view programming.
Even so, consumer demand won't be the main driving
force in the transition from 20th-century broadcast TV to
21st-century IPTV—at least, not to begin with. In the last decade or so, traditional telephone
companies, faced with competition from cable-based rivals, have had
no choice but to redefine themselves as information service
providers, offering Internet connectivity as well as phone services.
The more powerful and enterprising among them now see a further
business opportunity by redefining themselves so they offer
telephone, Internet, and TV services simultaneously. Cable companies
already offer all three services in attractive bundles; IPTV makes it
possible for telephone providers and broadcasters to join forces and compete.
In the longer term, who knows whether people will even regard TV, telephone,
and the Internet as separate entities, or whether they will continue to
converge and merge?
Delivering IPTV sounds easier than it may prove in
practice. The biggest inhibitor at the moment is that too few homes
have broadband connections with enough capacity to handle a single
high-quality TV stream, never mind several simultaneous streams (if
there are several TVs in the same home). Upgrading ordinary broadband
connections to fiber-optic broadband, so they routinely provide homes with 10–100Mbps, will take
time and considerable investment. Until that happens, IPTV providers
will not be able to guarantee a "quality of service" (often referred to
as QoS or sometimes a "quality of experience," QoE) as good as TV delivered through cable, satellite, or
across the airwaves. Latency (delays in packet arrival) and
packet loss are problems enough for VoIP (Voice Over Internet Protocol)
telephones, and they become much more of an issue when
broadcast-quality video is added into the stream. Since IPTV uses
compressed video formats such as MPEG2 and MPEG4, packet loss has a
much more serious effect than it would have on uncompressed video or
audio streams: the higher the compression rate, the bigger the effect every lost packet has on the picture you see.
With luck, IPTV may take off in exactly the same way as broadband Internet did in the early 2000s: back then, as more people
used the Internet, they felt hampered by the limitations of dial-up connectivity,
demanded (and showed they were willing to pay for) higher-quality
broadband, and provided enough revenue for the telecommunications companies to upgrade their networks. Once viewers start to experience
the convenience, control, and interactivity of IPTV, higher bandwidth Internet connections that make it possible seem certain to follow.
Find out more
On this site
On other sites
- IPTV News: Portal for people interested in IPTV.
- Flowing Internet Video Streams Through the Television by J.D. Biersdorfer. The New York Times, July 29, 2016. A very quick, hands-on introduction to adding Internet-streamed services to your existing TV.
- Best media streamers 2016: What's the best media streamer?: PC Advisor, 6 January 2016. A no-nonsense comparison of set-top boxes and dongles from Amazon, Google, Apple, Roku, and other rivals (geared to UK readers, though of broader interest too).
- UK most advanced TV-watching country in world, research finds by Jasper Jackson, The Guardian, 10 December 2015. Thanks to BBC iPlayer and services such as Amazon Prime, over 70 percent of adults now watch TV online in Britain.
- Amazon launches TV streaming and gaming device: BBC News, 2 April 2014. Amazon goes head-to-head with Google's Chromecast and Apple TV in the battle for online television.
- An inside look at a Verizon FiOS Super Headend and Video Hub by Ben Drawbaugh, Engadget, 17 December 2009. A tour of Verizon's IPTV headquarters in Temple Terrace FL.
- IPTV: Reinventing Television in the Internet Age by Greg Thompson and Yih-Farn Robin Chen, Computing Now, June 2009. A leading IPTV architect sketches out his vision of the future.
- The future of TV lies on the net by Dave Lee, BBC News, 9 March 2009. Describes the BBC's IPTV initiative, Project Canvas, and why IPTV appeals to broadcasters as a way of targetting advertising much more precisely.
- Q&A: Internet Protocol TV: BBC News, 9 March 2005. A basic introduction geared to ordinary TV viewers.