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 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).
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").
What is the "Internet Protocol" in IPTV?
IPTV stands for
Internet Protocol TV—but what does "Internet Protocol" mean? It's the
essence of how the Internet works.
Send an email to
a friend or download a web page and the information you set in motion doesn't
travel in one big lump, as you might expect. Instead, it's broken up into lots
of small pieces, known as packets, each of which may be
"switched" (sent) to its destination by a different route. Packet
switching, as this is known, is the basic principle of how any information
travels over the Internet. The computers that link the Net together don't know
what any given packet means or what it does. All they know is the IP
address (a numeric "house and street name" given to every
computer on the Internet) where the packet has to go—and they treat all packets
equally.
The Internet
isn't designed to do a particular job, such as delivering emails: it's simply a
highly efficient, computerized "postal" system for delivering
zillions of packets. The simple but amazing consequence of this is that as long
as you can turn information into packets, you can send it over the
Internet—whatever the information might be. That's why the Internet can be used
for sending emails, downloading web pages, making telephone calls (using a
technology known as VoIP (Voice Over
Internet Protocol), watching
TV—and doing a dozen other things that have not yet been invented. If someone
had designed the Internet more rigidly, purely for shuttling emails for
example, using it for other things, such as telephone calls or TV, might not
have been possible.
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?
Storing programs
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.)
Preparing programs
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.
Streaming programs
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).
IP multicasting
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 video stream.
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.
IPTV protocols
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).
Managed networks
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.
Viewing programs
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 or computer and connects via
Wi-Fi to the Internet to download TV programs, movies, and music. Google's
Chromecast works this way.
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.
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