Online video basics – Definitions of commonly used terms
Bandwidth
Bandwidth is defined as a data transmission rate; the maximum amount of information (bits per second) that can be transmitted along a channel. If you think of the communications path as a pipe, then bandwidth represents the width of the pipe that determines how much data can flow through it at once.
Bit rate
Bit Rate refers to the rate at which ‘bits’ of data are transferred across a network. It is usually represented as ‘Kbps’ which stands for Kilo Bits per Second.
Buffering
Buffering is where a stream of data begins before the media file actually plays. This data goes to local storage so that the incoming data always stays ahead of the actual data being viewed.
Bit
Describes the smallest unit of storage in a computer. It has a value of 0 or 1. Eight bits make up 1 byte, which can store one letter, number or symbol.
Broadband
Describes a high-speed network connection (T-1, DSL, cable modem), as opposed to a dial-up connection, which can only transfer data at a speed of 56Kbps.
Buffering
Buffering is where a stream of data begins before the media file actually plays. This data goes to local storage so that the incoming data always stays ahead of the actual data being viewed.
Byte
Describes a unit of storage that can contain one letter, number or symbol. Consists of 8 bits.
Capture
The process of changing or transferring digital or analogue audio or video files to binary files, which can then be edited and compressed.
Compression
The process of compressing audio and video signals for the purposes of streaming. This can be done using hardware or software. The streaming files are decompressed at the user’s end using a ‘player’.
CDN (Content Delivery Network)
A company that delivers streaming media via an intelligent distributed network. This means that audio or video streams will be delivered more reliably, with less buffering and time outs. Generally, this will provide a better overall experience for the end user.
CODEC
Stands for Compress/Decompress. An algorithm or formula is used to code and compress the media file, which is then decoded and decompressed as the user views or listens to the file.
Delivery modes
Files can be delivered as a progressive download or streamed from a streaming server. See http://blog.mydeo.com/2009/01/12/streaming-vs-progressive-download-understanding-the-difference/ for more information about delivery modes.
DSL
Digital Subscriber Line. DSL uses unused portions of a phone line’s bandwidth for transmitting data at high speed.
Embedded player
A player placed within a browser window so that only the video shows.
Firewire
Sometimes referred to as DV, iLink or IEEE1394, Firewire allows very fast data transfer, so is ideal for transferring footage from your digital camera to your PC.
FPS (Frames Per Second)
The number of video frames displayed each second. The higher the number, the smoother and sharper the images appear. Sometimes referred to as Frame-rate.
Hosting
Storing media files on servers specifically designed for streaming over the internet.
Kbps
Stands for Kilo Bits Per Second and refers to the rate at which ‘bits’ of data are transferred across a network or internet.
MPEG
MPEG is a digital video and audio compression format that was defined by the Moving Pictures Experts Groups, which is part of the International Standards Organization (ISO).
Packet loss
Data is transmitted in small units known as packets. Occasionally, packets are lost or delayeddue to network congestion, resulting in dropped frames.
Pixel
One unit of screen information. A video image is composed of individual coloured dots, referred to as pixels. Depending on how a monitor is set, a pixel can take up 8 bits/1 byte (256 colours), 16 bits/2 bytes (high colour), or 24 bits/3 bytes (true colour).
Player
Compressed files are decompressed when they reach the viewer using a ‘player’. The most common players are Microsoft’s Windows Media Player, Real Networks’ RealPlayer and Apple’s QuickTime player. If files are compressed using Microsoft’s compression software, the viewer will need the Windows Media Player. If files are compressed using Real’s compression software, the viewer will need the RealPlayer, and so on.
Progressive download
A method of delivering audio/video data over the internet that involves playing the downloaded portion of a file while the download is still in progress.
RealVideo
The file format developed by RealNetworks, used to stream video over the internet.
Streaming media
Streaming media allows the user to watch or listen to a media file without downloading it. The file is simultaneously ’streamed’ to the user as he or she is watching or listening to it. The user needs a player to view or listen to the files – files must be decompressed by a media player that is compatible with the format of the file. Streaming media technology enables the real time or on demand distribution of audio, video and multimedia on the internet. A streamed file is simultaneously downloaded and viewed, but no physical file is left on the viewer’s machine.
Throughput
The total amount of data transferred over a period of time – normally represented as MB or GB
VOD (Video On Demand)
Video that can be accessed at any time by the user.
