BT video streaming spells trouble for 3G
Published: 30 Apr 2003 16:39 BST
BT has developed a method of streaming video across GPRS networks that it claims will eliminate the problem of delays and disjointed, choppy playback.
The system, called Fastnets, was developed by BTexact at Adastral Park, where it was demonstrated earlier this month.
According to BT, the system does not suffer from the buffering problems typically associated with video streaming across both mobile and fixed-line networks due to changes in the connection speed.
In the demo, the telco showed that a video stream continued without a pause, rather than faltering, when the mobile network suffered significant drops in data transfer rate. The video stream also began playing almost immediately after being activated by the client device, as opposed to the user having to wait while the first few seconds of data were downloaded to the device's memory buffer.
A BT researcher explained that the Fastnets system could adapt to changes in network conditions, to maintain a constant stream.
This is possible because the server supplying the video has several different versions of the same content, recorded at different frame rates. When a video starts, the server transmits the content at a low frame rate to ensure that the stream can begin quickly, and starts filling the buffer with the next few seconds of video.
The server then monitors both the speed of the connection and the amount of data stored on the client's buffer. When the buffer is full, it switches to a higher frame rate -- giving the user a better quality recording.
This switch to a higher frame rate recording means that more data has to be transmitted per second. If the connection rate then drops so that the video is no longer being transmitted as fast as it's being seen, the buffer will begin to empty. In response, the server will return to the lower frame rate -- which is of a lower quality but requires less data.
The demonstration showed how a video stream of a horse race would switch between 6 frames per second and 25 frames per second, depending on the connection rate supported by the GPRS network.
According to BT, Fastnets could support applications such as remote surveillance or mobile post cards, as well as being used for news and sports reports.
BT is already in discussion with a number of GPRS operators, who it says are interested in using Fastnets commercially. If deals are struck, it could be bad news for 3G.
Streaming video is seen as one of the key applications that will tempt users onto third-generation networks. If GPRS can support streaming video well enough, people could resist such a move.
Several other companies and research teams are also working on ways of improving streaming video, including the University of California which has developed a new coding technology that it says will double the quality of videoconferencing over a mobile phone.
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