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This glossary begins as Appendix 1 in Web Radio. Radio Production for Internet Streaming. As I come across new terminology or definitions that apply to web radio users I'll add them to it.

Glossary last updated 6 June 2002

A

ADSL

Asymmetric Digital Subscriber Line. A technology upgrade to a local telco exchange which converts a normal copper wire phone line to a broadband connection for domestic receivers. 'Asymmetric' refers to there being a higher bandwidth available for incoming signals than outgoing.

Airport

Apple's wireless (q.v.) technology which allows multiple computers to be networked together using radio frequencies (RF).

Algorithm

A complex mathematical formula which defines a sequence of steps or computations. In this context any formula which compresses digitised sound data.

AM

Amplitude Modulation: the first of the two technologies for transmitting analogue sound on radio waves.

Analogue

Applied to radio, as opposed to digital. Adjective describing the carriage of sound in the form of continuously varying electrical current and/or continuously varying electromagnetic signals.

Archive

In streaming terminology this is interchangeable with 'on demand'. However it should not be confused with archive in the sense of keeping a permanent audio record, e.g. on CD.

ASF

Microsoft Windows proprietary streaming file format for Media Player, Active Streaming Format.

Audion

A software product developed by Panic for storing, sending or receiving MP3 streams on a Macintosh computer.

Archiving

Storing encoded audio on a server ready for streaming on demand.

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B

Bandwidth

The capacity of an Internet (i.e. phone) connection. Measured in bits per second, or the SI multiples: kilobits (thousands), Megabits (millions) or Gigabits (thousand millions)

Bit

The smallest unit of binary computer code: a one or a zero. In electronic terms a command to switch micro-current either off or on.

Bit depth

The resolution of a digital sample of sound. The higher the bit depth the higher the fidelity across the full range of sound frequencies.

Bitrate (or bit rate)

An expression of bandwidth: the rate of bits transmitted or passing per second.

Bluetooth

An 'open source' (i.e. non-proprietary) standard or version of wireless (q.v.) technology, which allows multiple computers or microcomputers to communicate together using radio frequencies (RF).

Browser

A software application which give you access to the Web, such as Netscape or Microsoft's Internet Explorer.

Byte

The standard unit of stored binary data, equal to eight bits.

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C

Circuit switching

'Old fashioned' phone technology which 'engages' a route between two phones as a continuous connection for the duration of the call.

CODEC

A name given to any proprietary software which COdes and DECodes data. In the context of web radio the major streaming CODECs are the Real, Windows Media and MP3 formats.

Co-location (or colo)

A secure facility designed to house Web servers securely, with a regulated, backed up power supply and dedicated internet connections.

Compress

1. (Traditionally) To squeeze a sound signal electronically in order to reduce the difference in volume between the quietest and loudest parts of the signal. Typically applied prior to transmission to boost average analogue or digital broadcast levels, the better to 'cut through' noisy listening environments, especially the car.

2. (In streaming) To massively reduce the size of a digitised audio or video file for streaming, by applying a specialist algorithm or software CODEC, e.g. MP3.

CPU

Central Processing Unit. The heart of a computer; its micro-processor or micro-chip, which processes binary data. The speed of the CPU (in Megahertz, MHz) or multiple CPUs determines how long the user has to wait for anything to happen on their computer.

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D

DAT

Digital Audio Tape. One medium for storing recorded sound, usually at very high quality, in digital form. A professional format.

DSL

Digital Subscriber Line. The generic term for a range of differing technologies for massively increasing the data capacity of phone lines, of which ADSL (q.v.) is one.

DSP

Digital Signal Processor.

Data rate

The same as bit rate or connection speed.

Decompress

The receiving side of definition 2 under 'compress', above.

Digital Audio Broadcasting (DAB)

Both a generic term and the proprietary name given to a transmission system for radio which uses parts of the upper end of the VHF spectrum. Around eight stations are bundled together into 'multiplexes' of simultaneous transmission on a given receiving frequency.

Digitalisation

(As opposed to digitisation, q.v.) Generally applied to the conversion of an entire production operation (e.g. radio broadcasting, or newspaper layout and printing) from analogue technology to digital technology.

Digital Millennium Copyright Act (DMCA or DM Act)

An influential piece of legislation, which was passed into American law in 1998 in order to protect copyright holders from the effects of digitalisation.

Digital Radio Mondiale (DRM)

A transmission technology for converting radio signals in the AM spectrum from poor quality analogue into high quality digital sound. (See also DAB)

Digitisation

The conversion of analogue information into digital data.

Direct Satellite Broadcasting

As distinct from terrestrial broadcasting, the transmission of radio or TV stations via satellite, direct to domestic receivers, which typically incorporate some form of dish.

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E

Edge services

Specialist multimedia Internet services whose physical location close the highest bandwidths at the core of the Internet allow them to guarantee the most reliable connection and high data rates.

Electrophone

Earliest use of the telephone network for transmitting public sound narrow-casts via local exchanges, before the invention of analogue radio.

Encode

Convert an analogue or digital sound (or video) signal into one of the streaming formats (e.g. Real, WMP, QuickTime, MP3), prior to distribution on the Web by a suitable streaming server.

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F

Firewall

A general term for security software that protects a computer network connected to the Internet. It prevents anyone gaining unauthorised access to the network from an outside computer - and therefore can present a barrier to streaming if not configured appropriately.

FM

Frequency Modulation. The second of the two technologies for transmitting analogue sound on radio waves.

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G

2.5 G

A tag given to the GPRS (q.v.) mobile phone system. (If WAP is the 2nd generation and UMTS will be the 3rd, then GPRS is half way between.)

3 G

A tag given to the 3rd generation of mobile phones, UMTS (q.v.).

GPRS

General Packet Radio System. The mobile phone protocol that aims to succeed WAP (q.v.). Because it is packet switched it is always on and can carry data much faster than the circuit switched systems before it.

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H

Hub

A type of junction box on a computer network. It is a passive device, as opposed to a 'switch' which can actively assign pathways.

html

Hyper-Text Mark-up Language. The main coding standard for creating web pages so they can be read by browsers. The file extension thereof.

http

Hyper-Text Transport Protocol. The coding standards which govern the transfer of web pages between servers and client computers on the Web.

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I

ICT

Internet and Communications Technologies.

IEEE

Institute of Electrical and Electronics Engineers

i-mode

A mobile phone system capable of accessing appropriately coded web pages, developed by the Japanese telco, DoCoMo. Roughly equivalent to WAP (q.v.).

Internet

The global network of computers made up of a collection of inter-connected sub-networks.

Intranet

A network of computers within a business or organisation.

IP

Internet Protocol. Part of the universal system of standard protocols which are the basis of packet transmission. The other part is Transmission Control Protocol (TCP).

IP address

The unique numeric address of a connection to the Internet.

ISMA

Internet Streaming Media Alliance.

ISP

Internet Service Provider.

ISPA

The Internet Service Providers' Association.

ISRC

International Standard Recording Code. A code embedded in the digital data of a published recorded music track. This system is in the process of being introduced by major record labels as an anti-piracy measure. It is administered by the RIAA (q.v.).

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K

Kbps

Kilobits per second. The usual unit in the measurement of the speed, or capacity, of an Internet connection.

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L

LAN

Local area network. A small network of computers.

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M

m3u

The name (or file extension) given to encoded sequences of MP3 files.

Mbone

A multicast (q.v.) enabled route through the Internet.

Mb

Megabit (see bit).

MB

Megabyte (see byte).

Mbps

Megabits per second: the unit for measuring the capacity of fast Internet connections.

MD

MiniDisc: a medium now widely used for storing digital audio. Uses heavier compression than CD or DAT, but provides excellent sound quality for routine radio uses.

Media Player

1. The generic term for any software plug-in which plays back streaming audio or video.

2. A common abbreviation of the Windows Media Player plug-in.

MHz

Megahertz: millions of cycles per second. A measurement of frequency.

MP3

Abbreviation of one very widely used compression standard. Short for MPEG II, layer 3. Layer 3 refers to the complexity of the algorithm and is an indicator of the processing power needed to run it.

MPEG

Moving Picture Experts Group. The general term applied to any compression algorithm for audio and/or video devised under their supervision.

Multicast

A mode of Internet distribution which allows a single output from one server to be repeatedly split by 'multicast enabled' routers and hence available to multiple connections. Therefore unlike unicast (q.v.) it can only be used to receive live streaming and not for on-demand.

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N

NAN

Neighbourhood Area Network. A term used to describe a small network of computers connected to the Internet via a shared broadband connection by means of Wi-Fi (q.v.) links. An activists term for wireless LAN (q.v.).

NMPA

National Music Publishers Association. Influential body representing the US music publishers.

Net congestion

The common cause of break-up of audio steams, which occurs when Internet traffic comes close to the capacity of regions of the telecoms network. Particularly noticeable when, for example, East Coast America wakes up and starts getting online en masse.

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O

OFCOM

Office of Communications: the UK government's proposed new multimedia and telecommunications regulator.

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P

Packet

The standard unit of data that is sent across the Internet. Typically comprises 1,024 bits of data. This includes a section of the message plus a 'header' which details the destination IP 'address', the sender's IP 'address', a check digit which confirms the data has not become corrupted and the packet's position in the sequence of the message.

Packet switching

As opposed to circuit switching. A digital switching technology which massively improves the efficiency of telecoms pathways by making them continuously available for multiple simultaneous connections. This is possible when data passes through such a system as packets rather than complete messages.

Portal

An Internet site which acts as a gateway or guide to the Web. Inevitably each portal specialises in particular kinds of sites that are likely to be popular with its regular users.

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Q

QuickTime

Apple's streaming software.

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R

Radio

Originally the shortened form of radiotelegraphy, derived from radiant or radiating, and applied to its apparatus. Subsequently radio-telephone (point to point) and later the receiver for sound broadcasting (one to many).

RAM

Random Access Memory. The measure of the amount of space available for storing files on a computer's hard disk.

RealPlayer

The software helper application need to receive Real audio and video streams.

Re-purposed

An adjective often used for streamed content that was originated for analogue broadcast. This may be the same as simulcast or else refer to archived material.

Resolution

The detail contained within each sample in the process of digitising sound. Along with the sample rate (q.v.) this determines the limits of accuracy or fidelity of digital sound. Measured in bits, hence also called 'bit depth'.

RF

Radio frequency. Describes the part of the electromagnetic spectrum used for transmitting signals - typically in connection with remote control wireless technology.

RIAA

Record Industries Association of America. The highly influential body that lobbies on behalf of the major international record companies.

Ripping

Digital audio extraction. Copying directly (i.e. digitally) from an audio CD format into a sound file format on a hard drive.

Router

A specialised computer which selectively routes data to different destinations on a network. Routers are therefore the motors of the Internet (and the packet switched phone system), receiving packets of data, reading their header codes and re-sending them on to the next available router towards their destination.

RTP

Real-time Transport Protocol. An open standard file transfer protocol suitable for streaming. Used by QuickTime among other formats.

RTSP

Real-time Streaming Protocol. The request, on demand side to RTP in a unicast streaming set-up.

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S

Sample rate

The number of times per second an analogue current (carrying a sound signal) is sampled in the process of digitisation. Along with the resolution (q.v.) of samples this determines the accuracy or fidelity of digital sound.

Server

Any computer that distributes ('serves') data across a network. In the context of streaming it is typically a specialised machine with one or more fast processors and plenty of memory.

SHOUTcast

One of the major software products for streaming MP3 files, made by Nullsoft.

Simulcast

Distribute radio (or TV) content through more than one outlet at the same time. Originally applied to radio stations which broadcast identical content simultaneously on more than one frequency (e.g. on FM and AM), it is now applied to analogue or digital broadcasts which are simultaneously webcast.

Standard

A universally or widely authorised and freely available (i.e. non-proprietary) file format, computer code or language. e.g. WAV or MP3 are standard audio file formats; html is a standard language for building web pages.

Stream

Verb or noun describing the process of transmitting digitised audio (or video) across the Internet so that it can be heard or viewed in real time.

StreamWorks

An early, high quality audio and video streaming system based on MPEG files, developed by Xing Technologies, now part of Real Networks.

Strip scheduling

Regularised, fixed scheduling, which places the same programme or type of programme in the same time slot every day - in a strip across a 5 or 7 day weekly schedule. The framework of format radio.

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T

Telco

Short for telephone company.

Terrestrial transmission

Broadcasting from a radio wave transmitter.

Time shifting

Listening to programmes at a time determined by the listener, not by a transmission schedule. In web radio this is made possible by on demand or archived streams.

Timed out

An error message received when a media player has repeatedly tried and failed to establish a stream. It is controlled by an option in the set-up of the server which sets a time limit for a stream to be established successfully or else aborted.

TiVo

An early proprietary example of a digital television which incorporates a high capacity hard disk recorder for storing hours of programming.

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U

UDP

User Datagram Protocol. An alternative, faster Internet file transport standard to TCP/IP (q.v.) Used by the QuickTime CODEC and other RTP/RTSP compatible formats.

UMTS

Universal Mobile Telecommunications System. The transmission standard for the forthcoming '3G' global mobile phone network.

Unicast

The usual mode of streaming which involves maintaining a one to one dialogue between each receiver and the streaming server. As opposed to multicast (q.v.)

UPC

Universal Product Code. The unique identification number which appears along with the bar code on the side of most consumer products, including - of interest here - CDs, vinyl disks, audio cassettes, etc. Used for identification purposes when stations log their music output.

URL

Uniform Resource Locator. The standard form of address for locating a web page.

USIIA

United States Internet Industry Association.

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V

VBR

Variable Bitrate. A software function which detects the end to end bandwidth available for a streaming connection and automatically adjusts the output from the server accordingly.

VDSL

Very high data rate DSL (q.v.) Currently in development. Intended to offer TV quality data rates through phone connections over short distances, e.g. between a local fibre optic link and the subscriber.

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W

WAP

Wireless Application Protocol.

Wi-Fi

Another term for wireless networking technology, specifically using the IEEE (q.v) standard, number 802.11b, which in many countries can be used to transmit legally and without license on unreserved frequencies. Combined with a DSL, cable or satellite broadband Internet connection Wi-Fi technology is now being used experimentally in some localities to stream high quality radio via the Web.

WIPO

The United Nations World Intellectual Property Organisation.

WMP

Windows Media Player, the client software for Microsoft's proprietary streaming format.

Webcasting

Generic term for transmitting audio or video content (with accompanying website text) on the Web using streaming software.

Winamp

Nullsoft's PC based receiver for streaming MP3

Wireless

A word which has been used to describe successive technological revolutions in radio's history. Originally applied to analogue radio sets with internal speakers (though they were still wired to mains electricity), it now describes technologies which link computers and their peripheral hardware by means of remote radio signals instead of wires or cables.

Wireless broadband

The marriage of broadband and wireless technologies to give high quality remote access to the Internet - a 'holy grail' for the Internet in general and streaming technologists in particular.

Wireless Internet

Connection to the Internet via satellite or a terrestrial transmission network, instead of through a phone cable. Currently through WAP or iMode (q.v.) or else via direct (one or two way) satellite connections which some specialist service providers make available at a price.

Wireless LAN

A LAN connected by Wi-Fi technology (q.v.).

wLAN

short for wireless LAN (q.v.)

World Wide Web

The most widely accessed part of the Internet, unified by the computing standards laid down by W3C, the World Wide Web Consortium.

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X

Xing

A software company that developed StreamWorks, an early, high quality audio and video streaming system based on MPEG files. Now part of Real Networks.

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Z

Zoning

(as applied to the World Wide Web) A measure advocated by some for separating out Web content into clearly identifiable categories (zones) to make it more amenable to regulation or to enable entry barriers to restrict or charge for access to different types of content.

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