Stream quality refers to the quality of the image and audio transferred from the servers of the distributor to the user.
Higher-quality video such as video in high definition (720p+) requires higher bandwidth and faster connection speeds. The general accepted kbps download rate needed to stream high-definition video that has been encoded with H.264 is 3500, where as standard-definition television can range from 500 to 1500 kbps depending on the resolution on screen.
In the UK, the BBC iPlayer deals with the largest amount of traffic yet it offers HD content along with SD content. As more people get internet connections which can deal with streaming HD video over the internet, the BBC iPlayer has tried to keep up with demand and pace. However, as streaming HD video takes around 1.5 gb of data per hour of video it took a lot of investment by the BBC to implement this on such a large scale. For users which do not have the bandwidth to stream HD video or even high-SD video which requires 1500kbps, the BBC iPlayer offers lower bitrate streams which in turn leads to lower video quality. This makes use of an adaptive bitrate stream so that if the users bandwidth suddenly drops, iPlayer will lower its streaming rate to compensate for this.
This diagnostic tool offered on the BBC iPlayer site measures a user's streaming capabilities and bandwidth for free. Although competitors in the UK such as 4oD, ITV Player and Demand Five have not yet offered HD streaming (2010). The technology to support it is fairly new and widespread HD streaming is not an impossibility. The availability of Channel 4 and Five programs on YouTube is predicted to prove incredibly popular as series such as Skins, Green Wing, The X-Factor and others become available in a simple, straightforward format on a website which already attracts millions of people every day.