ADSL is just one type of Digital Subscriber Line, it is a high speed transmission over twisted-pair copper wires. It is an asynchronous transmission method, which means that download speeds are faster than upload speeds. Speeds range from 512Kbps through to 8Mbps - this depends on your provider, quality of the line and proximity to a telephone switching station. ADSL is primarily a consumer product, meaning the majority of people use it for downloading "large" amounts of information and comparatively send out only "small" amounts of information. This asynchronous nature means that an ADSL line can receive a high quality stream, but cannot send one out. Because of this, when choosing what quality to send out a live webcast you should check with your ISP to find out the available upstream.
AIFF is a file format used to store MIDI information - high quality sampled audio and musical instruments. In terms of size and quality AIFF files are similar to WAV files. Audio programs available on both Mac and PC can usually read AIFF files, despite them being originally created by Apple.
An Algorithm is a mathematical formula which seeks out and replaces repetitive data with code. Advanced algorithms even consider the limitations of human perception - such as the formula to determine the compression and decompression of data.
Also known as a Repeater, an Amplifier is a component in a network that increases the power of a signal when attenuation causes it to be lost. This allows greater distances to be covered in a LAN environment.
Electronic transmissions that are sent by adding signals of varying frequency or amplitude to carrier waves of a given frequency of alternating electromagnetic current are referred to as Analog. Conventionally, broadcast and phone transmissions have used analog technology as does the process of recording onto standard audio and videotape - this is done in a continuous wave, rather than digitally in a binary form.
An Animated GIF uses multiple GIF picture files in quick succession to simulate movement. Unlike more advanced animation forms such as Java, Shockwave or Dynamic HTML - animated GIFs do not require much programming or design skills. The most common use for animated GIFs is moving logos on websites.
Animation is created by a series of still images being displayed in quick succession to simulate motion. Examples of web animation include Animated GIFs, Flash and Shockwave.
The Application Layer dictates program to program communications as well as how applications access network services. These include file transfers, job transfers and terminal emulation.
Sometimes referred to as 'noise', Artifacting is the distortion that occurs when audio or video is compressed to a very low bit rate.
Different to an ASX file, an ASF file is an actual audio/video file. Most streaming media files encoded for intended use with Windows Media have the .asf extension.
An ASX is a metafile (or pointer file) for Windows Media that points to a Windows Media audio/video presentation.
Asymmetric refers to a network connection that has unequal upload and download speeds, such as ADSL.
ATM is a network protocol designed for the purpose of moving multimedia data with a higher level of reliability and speed. ATM allows a bandwidth of 25Mbps to 622Mbps
A Microsoft format for the saving of audio/video clips. The files can be played through Windows Media Player or several other Multimedia Players.
The high bandwidth routes joining networks together is known as the Backbone and is currently made up of OC-48 and OC-3 links.
Bandwidth is the level of throughput available on a connection. Though not entirely accurate, many use the term bandwidth to describe the amount of data that can be transferred in a fixed amount of time. In this case digital devices are measured in bits or bytes per second while analog devices are measured in Hertz (HZ).
A Bit is a Binary Digit, a unit of information. It is a computational quantity that has one of two values that is represented by a 1 or 0 as the yes/no answer to a digital question.
Bit Rate is the speed at which data travels, the rate of data transfer when media is being streamed from one place to another on a computer network, for example the Internet.
Bits per Second is the measurement of how many bits are being transferred each second.
A Bridge serves to extend the range of a network by connecting two LANs - they check the data and then forward it across LANs.
Broadband is a term given to a network connection which supports a relatively high bit rate.
A Broadcast is a transmission that is sent simultaneously to all stations on a network.
Buffers store audio/video data until there is enough for the stream to be composed - it is a space allocated on the RAM (Random Access Memory) of a system where the data can be temporarily stored until it is transferred to another part of the system.
Buffering is when a media player is saving part of a streamed media file locally for playback - this process ensures constant playback as well as the integrity of the stream. This small percentage of the presentation is buffered before beginning to play it and compensates for fluctuations in the available bandwidth on the connection.
Bus Topology refers to a LAN structure in which all nodes are connected to the same cable which transmits all data.
A Bypass infers the use of transmission facilities which avoid local telephone networks, usually for data.
A Byte refers to a block of 8 bits of data.
Bytes per Second is the measurement of how many Bytes (8 Bits) are transferred each second.
A Cable Modem is a device that allows an Internet connection over a cable network of optical fibre thus allowing for much higher speed connections.
A Cache is a memory store where content is stored that is accessed frequently - this enables it to be accessed much faster than if it was in normal memory.
Capture refers to the process of digitising audio/video content from an analog format. Also referred to as Digitising.
A Capture Card is a device that creates media from an audio/video feed and turns it into a digital format.
CDMA spread information in a specific signal over a greater bandwidth than the original signal.
A CDN is a company that specialises in delivering Web Data (including streaming media) around the world via an intelligent distributed network - PlanetStream is an example of a CDN. Being a CDN, rather than a standard streaming provider means audio/video streams are delivered more reliably, in higher quality and with less buffering - all of this provides a better media experience for the end user.
Circuit Switching is used when data must be sent quickly and remain in the same order, as with live audio and video - it achieves this by establishing a dedicated circuit for the duration of the transmission.
A Coaxial Cable is a copper construct consisting of a central wire encased in insulation an then a grounded shield of braided wire. Being less prone to interference, it is often used in television and computer industries.
A Codec is an algorithm used for encoding audio/video into a file to be played back by a media player. It allows an operating system or a program to properly play in a particular format.
Compression is used to reduce the size of data, saving space or transmission time.
A Contention Ratio refers to the number of users sharing a network connection.
Data Rate is the speed at which bits of information are transmitted per second.
A Data Transfer is the amount of data being transmitted between computers and in terms of streaming is usually measured in MB (Megabytes) or GB (Gigabytes).
A Database is a collection of sets of data.
Dial-Up Access refers to a usually low bandwidth connection whereby users hook up to a network on a pay=per-time basis.
Digital technologies generate, store and process data in terms of binary code including either 1's or 0's.
Digital video is usually converted from an analog source and a digital signal is represented by binary code, 1's and 0's.
DRM from Microsoft allows a piece of content to be encrypted. When a user tries to play the content their license is checked and where appropriate they are then forwarded to a license server where they must either enter a password or purchase a license to view the content.
DS-3 is a high speed network at 45Mbps.
DSL technologies use sophisticated modulation schemes to pack data onto copper wires. The two main types of DSL are ADSL (Asymmetric) and SDSL (Symmetric)
A DSP is an optimised chip that performs repetitive mathematical tasks like encoding and decoding.
Encoders are hardware or software that use Codecs to generate digital media files.
Encoding is the process of generating digital media files by compressing video using a Codec.
A Firewall is a piece of software or hardware that blocks traffic on particular ports, increasing security on a network.
A Firewire is a new standard that means digital video cameras and other external devices can transfer data to a computer at very high bit rates (up to 400Mbps).
Flash, from Macromedia is a vector-based format used for narrative productions on the web.
Flash Streaming is the streaming format from Macromedia. Available for Live Events as well as Video On Demand, Flash has the widest compatibility with computers.
FPS is the measurement of the number of frames which are displayed each second during video playback.
The Frame Rate is the number of frames of video displayed during a given time.
Gigabits per Second is the measurement of the number of Gigabits of data transferred over a network every second.
A Gigabit is 1,073,741,824 bits and is calculated from raising 2 to the 30th power.
A Gigabyte is 1,073,741,824 bytes or 1024MB.
GPRS is used by some mobile phones as an Internet connection and can see speeds of up to 115Kbbps - due to the smaller screens on phones this can provide deceptively high quality viewing.
GSM is a digital and wireless technology which has been standardised across Europe's wireless network.
Hot Colours may not appear as well as darker colours in streamed video and include bright blues, yellows and whites.
HTML is the formatting code used to create web pages.
HTTP is the protocol used to distribute web pages, normally on port 80. Streaming media can also be sent as HTTP to get around firewalls.
Interframe method is the type of video compression used in generating MPEGs.
An Interstitial is any web based advertisement occurring before, during or after a narrative content presentation and is best thought of the same way as television commercials.
IP is the protocol that determines how packets are formatted and addressed over the Internet. IP is part of the TCP/IP grouping of protocols.
An IP Address is a set of numbers used to uniquely identify a computer on a network.
An ISDN is a set of standards for the transmission of digital information over telephone lines - this allows for much higher speeds than a conventional modem.
An ISP is a company that provides connections to the Internet.
Kbps is a measurement of the rate at which data is sent over a communication line and is the most commonly used in streaming.
A Kilobit is 1,024 bits and is calculated from raising 2 to the 10th power.
A Kilobyte is 1,024 bytes.
Latency refers to the amount of time taken for data to complete a return trip between two points.
A Link is the Internet address of a reference file that holds information about where a media stream is located and how it can be accessed.
A Live Stream is audio/video media streamed in real time, there is usually a delay of between 5 and 30 seconds depending on the viewers available bandwidth.
Lossy Compression is an encoding method that removes redundant data in a file, compressing it more tightly.
M3U is a metafile that points to an MP3 stream.
Mbps is a measurement of bandwidth, a unit of the rate at which information is transferred. 1Mbps is equal to 1,000,000 bits of data being transferred each second.
Media Players are pieces of software used for the display and playback of audio/video streams.
A Megabit is 1,048,576 bits calculated from 2 raised to the 20th power and is equal to 1,024 Kilobits.
A Megabyte is 1,048,576 bytes and is equal to 1,024 Kilobytes.
A Metafile is a small file that at a minimum contains URLs of media file locations and points a media player to these streaming media sources. Metafiles commonly have the extensions .asx (Windows Media), .ram (Real Media) and .qtl (QuickTime).
MMS in this instance refers to the multimedia streaming protocol from Microsoft.
A Mount Point is a partition on a streaming server designated to a specific application or client.
Formally MPEG1-Layer3, MP3 is an audio compression algorithm.
MPEG is a lossy compression format which uses Interframe compression.
MPEG-1 is the video standard created by the Moving Picture Experts Group.
Commonly used for DVD recordings, MPEG-2 is an advanced standard created by the Moving Picture Experts Group.
MPEG-4 is a streaming standard created by the Moving Picture Experts Group. MPEG-4 is a Codec technology aimed at achieving interactivity, efficiency and stability in narrowband transmissions.
Multi Bitrate refers to a file that has been encoded with different bitrates for intelligent streaming playback.
A Multicast is a process allowing a server to send one stream to multiple recipients, unlike traditional streaming media where each user connects to a server separately.
The term Multimedia refers to the integration of text, graphics, audio, video and animation.
Narrowband is a term used to describe a network connection that supports a low bit rate or is sometimes used to describe content optimised for such instances.
Narrowcast is used to send data or a transmission to a very specific list of recipients.
Net Congestion describes a situation where there is significant delay between the sending and receiving of a transmission of data.
A Network is an interlinked set of computers communicating with each other using instruction sets (common protocols) such as the Internet.
New Media often refers to relatively new methods of media distribution such as CD-ROM, DVD and the Internet.
Nonlinear Editing is the process of editing audio/video when the entire track is available for mixing and matching.
Windows NT is a Microsoft operating system found on servers.
OC-3 is a 155Mbps high speed network.
OC-48 is a 2.488Gbps high speed network.
On Demand is the streaming of a pre-recorded piece of content initialised by the viewer in their own instance. The viewer has control over their viewing experience with regards to common DVD player commands such as Play, Pause, Stop etc.
Overheads refer to small quantities of data that are transferred for the purpose of sustaining a network connection - this in turn reduces the connections total throughput.
A Packet is data placed in a block for transmission over an IP network.
Packet Loss is when packets of data are lost in a transmission usually due to a slow or congested network - this results in audio gaps or video distortion.
PAL is the standardised protocol for television in Europe.
A Port is a channel used to communicate information over a network interface or protocol.
Port Forwarding is the process used to negotiate a route through a firewall.
Progressive Download is a method of playing part of a media file while the rest of it is still downloading, this differs from true streaming as it almost eliminates buffering without compromising on quality. The disadvantage is that it often requires a delay at the start of playback.
Protocols are an instruction set for the transfer of data and in streaming terms include RTSP, MMS and HTTP.
See Progressive Download.
A Pull is a connection initiated by a streaming server to receive a broadcast from a designated encoder for re-distribution across a network.
A Push is a connection initiated by an encoder to a streaming server to receive a broadcast for re-distribution across a network. This requires a username and password.
QuickTime is the multimedia architecture used by software tool vendors and content creators to store, edit and play synchronised graphics, sound video and music.
RAM is a metafile that points to RealMedia streams.
RealAudio is an audio streaming format created by RealNetworks.
RealFlash is a Flash presentation synchronised with a RealAudio soundtrack.
RealMedia is the streaming format created by RealNetworks.
RealVideo describes the file format from RealNetworks for audio/video.
Re-Broadcast refers to the re-distribution of a webcast from the encoder to multiple computers.
Caused by network congestion, Re-Buffering is when a media stream starts buffering part way through playback, it has to Re-Buffer due to the fact that all previously buffered data has been used up.
Rich Media is that which has been enhanced with animation or video.
A Router is a component in a network also serving as a Bridge.
RTP is a protocol that defines the streaming of real time audio/video data.
RTSP is the protocol used to deliver controlled amounts of streaming audio/video over networks.
SDSL is a line that provides equal upload and download speeds, making it much faster on upload that ADSL - ideal for live streaming.
Shockwave is the animation plug-in program from Macromedia that displays animation on the web.
Simulated Live is the term used to describe audio/video content that has been pre-recorded but is then broadcast at a specific time so that viewers must tune in to view it. This is largely used for Internet TV and Radio.
SMIL is a text based mark up language used to synchronise media elements including text, animations, audio and video into one media presentation.
SQL is used to manipulate data from a relational database.
Streaming is the process of sending compressed audio/video content from one computer to another across a network.
Streaming Media is a file that contains compressed audio/video content to be transferred from one computer to another across a network.
A Streaming Server is a server that has been specifically configured to deliver streaming media content to a client in real time.
T1 is a common digital leased line connection that is capable of carrying data at 1.544Mbps.
T3 is a digital leased line connection that is capable of carrying data at 44.736Mbps which is equal to 28 T1 lines.
TCP is a standard protocol for the transmission of text and ASCII data across IP-based networks.
Tunnelling refers to the encapsulation of one protocol within another - this is frequently used to transmit non-IP protocols across an IP network.
UDP is a fast method of communicating between computers which does not guarantee the delivery of every bit of information to its destination - this makes it ideal for time-sensitive data such as streaming media.
Unicast is a process where each clients media player connects to the streaming server individually.
UNIX is a generic term used to describe several similar server operating systems.
A URL is a path to a file on the Internet.
Video Compression is the process whereby a video file is reduced in size to be transmitted across a network.
Video Hotlinks are hyperlinks that have been embedded in video, users can click on certain parts of a video image to trigger an action such as a new media file or URL.
See On Demand.
VoIP is the practice of using an Internet connection to pass voice data from one computer to another in the form of a phone conversation.
A VSP is a company that specialised in the storage and transmission of streaming media.
The term Walled Garden refers to an environment on the Internet that is controlled by a specific entity.
WAP is the protocol that dictates delivery and access of information to wireless devices.
WAV files are digital representations of sound and can be identified by the .wav file extension.
A Webcast is an Internet broadcast delivered to a computer.
Webcasting is the act of sending a webcast over the Internet to a computer.
A Webisode refers to a single webcast episode.
Windows Media is the streaming media format from Microsoft.
Windows Media Audio describes an audio file format that can be associated with the Windows Media platform.