7.18 Internet TV & Telephony

Many now watch TV on their computers, or use the Internet to watch TV and make long distance calls.

Internet Television

Internet TV has become widely available, either as streaming services, or videocasts to be downloaded and played when convenient. Videocast downloads are straightforward, but can tie up a computer for twelve or more hours when videos are high definition, even with broadband connections. Streaming services have become more popular with such services as BBC iPlayer, 4 on Demand, ITV Player and Demand Five in the United Kingdom; Hulu and Revision3 in the United States; Nederland 24 in the Netherlands; ABC iview and Australia Live TV in Australia and Tivibu in Turkey. The services tend to be free (i.e. supported by advertising), and to use streaming technology rather than Peer to Peer networks. The services require considerable investment, both on the part of providers ( large server farms, mass storage, good sorting facilities) and customers ( broadband access, more used in Europe than the United States).

Several technologies are involved:

1. The Hybrid Broadcast Broadband TV consortium of industry companies is establishing an open European standard (HbbTV) applying to hybrid set-top boxes for the reception of broadcast and broadband digital television and multimedia applications with a single-user interface.

2. Current providers employ peer-to-peer (P2P) technologies, VoD systems, and live streaming.

3. The BBC iPlayer uses the Adobe Flash Player to provide streaming-video clips and other software provided by Adobe for its download service.

4. CNBC, Bloomberg Television and Showtime use live-streaming services from BitGravity to stream live television to paid subscribers under a standard http protocol.

5. DRM (digital rights management) software is employed to prevent copying for paid subscriptions, e.g. Microsoft's SkyPlayer, and Virgin Media's on-demand technology for BBC iPlayer and other services, including Wii and the PlayStation.

6. Internet TV is also available for mobile devices like the iPhone and iPod Touch, Nokia N96 and Sony Ericsson C905.

Higher-quality video requires bandwidths of 3.5 Kbps, standard-definition television bandwidths in the 500-1500 Kbps range (depending on screen resolution), and high-definition television rather more than 5 Mbps.

Internet Protocol Television

Put simply, Internet Protocol Television (IPTV) employs existing protocols to send compressed packets of TV digital content over the Internet. In fact, rather more than a computer and Internet connection are required. The elements involved are:

1. A TV head-end (i.e. station) where live TV channels are encoded, encrypted and delivered as IP multicast streams.
2. A VOD platform: where on-demand video assets are stored for customer access.
3. An interactive portal that allows the user to navigate within the different IPTV services.
4. A packet-switched delivery network that carries IP packets (unicast and multicast).
5. A home gateway: equipment at the user's home that links the delivery network to the user's setup box.
6. The user's set-top box, which decodes and decrypts TV and VOD content and displays it on the TV screen.

Many services are subscription-based, but an impressive and growing number are free, once equipment has been purchased and ISP charges paid. Services have been launched in most countries, and the number of global IPTV subscribers is expected to grow from 28 million in 2009 to 83 million in 2013. Europe and Asia are the leading territories, with China and India the fastest growing countries. World wide IPTV market revenues are forecast to increase from US$12 billion in 2009 to US$38 billion in 2013.


Many phone services— voice, fax, SMS, and/or voice-messaging applications—now use the Internet rather than the public switched telephone network. Several steps are involved:

1. Setup of the signal and choice of media channel.

2. Digitization of the analog voice signal.

3. Encoding, packetization, and transmission as Internet Protocol (IP) packets over a packet-switched network.

4. Reception of the IP packets and their decoding.

5. Digital-to-analog conversion to reproduce the original voice stream.

Transmission in detail is highly technical, with many protocols employed, e.g. H.323, IMP Multimedia Subsystem (AIMS), Media Gateway Control Protocol (MCP), Session Initiation Protocol (SIP), Real-time Transport Protocol (DTP) and Session Description Protocol (ADP). A major development was the introduction of mass-market viol (Voice over IMP) services in 2004, which use existing broadband Internet access to enable subscribers to make telephone calls as they would over the public switched telephone network. VoIP systems offer substantial economies, but may suffer from latency at high volume use, a consequence of packet loss and resending. Reliability is sometimes an issue when VoIP is used for emergency services, and the system is vulnerable to the usual Internet security problems ( insecure passwords, denial-of-service attacks, customer data collection, recording of private conversations, etc.) Governments have also become increasingly keen to monitor and regulate VoIP systems in the manner applying to public telephone networks.


1. Differentiate between videocasts and video streaming.
2. Explain the elements of Internet Protocol Television.
3. Describe some commercial applications of Internet television.
4. Outline the technology behind Internet telephony.

Sources and Further Reading

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