You’ve probably heard of the term ‘streaming’ but aren’t too sure what it means. Does it allow you to watch something live online? How does it work? This guide should answer your questions and clear up any confusion. WebWise Team | 10th October 2012 Streaming means listening to music or watching video in ‘real time’, instead of downloading a file to your computer and watching it later. With internet videos and webcasts of live events, there is no file to download, just a continuous stream of data. Some broadcasters prefer streaming because it’s hard for most users to save the content and distribute it illegally. How does it work? Streaming is a relatively recent development, because your broadband connection has to run fast enough to show the data in real time. Files encoded for streaming are often highly compressed to use as little bandwidth as possible. If there is an interruption due to congestion on the internet, the audio will drop out or the screen will go blank. To minimise the problem, the PC stores a ’buffer’ of data that has already been received. If there’s a drop-out, the buffer goes down for a while but the video is not interrupted. If there is no more data in the buffer, it will usually stop and display a message - ’buffering’ - while it catches up. Streaming has become very common thanks to the popularity of internet radio stations and various audio and video on-demand services, including Spotify, Last.fm, YouTube and the BBC’s iPlayer. Varying quality levels Some services offer different levels of quality for different internet connections. YouTube, for example, can stream low, medium and high-quality videos to both mobile phone users and broadband users. However, YouTube’s high-quality videos for phones (320 x 240 pixels) have less resolution than low-quality videos for PCs (400 x 226 pixels) because phones have smaller screens. Most people know that downloading files uses up their bandwidth allowance, which may be capped at a fixed number of gigabytes per month. But what they don’t know is how much bandwidth they use while streaming. Listening to music can consume about 0.5-1.0 megabytes per minute and watching ordinary YouTube videos can consume about 4-5 megabytes per minute. It can be more or less, depending on the quality. There are free programs that will measure bandwidth use, including NetMeter, Codebox Software's BitMeter II and FreeMeter Bandwidth Monitor For Windows. Some firewalls and some internet service providers (ISPs) will also tell you the amount of data used. One drawback with streaming is that there’s one stream per computer - ‘unicasting’. Broadcasters, including the BBC, would prefer to use ‘multicasting’, where everyone listens to the same stream. This would save a lot of expensive internet bandwidth and allow better quality streams. Multicasting is still in development.