Dynamic packet allocation [teletext service improvement]

This paper describes how the BBC has defined and installed equipment which has increased the efficiency of the use of the vertical blanking interval. This has brought visible benefits to the viewers by improving the speed of Ceefax, reducing access times typically by a sixth, without affecting the service given to Datacast customers. The editorial control of relative access times has been retained by operating the dynamic allocation on individual streams of text magazines. The broadcasters have acquired a greater understanding of packet by packet operations in the VBI, moving from allocation by line pair to processing packets individually. Teletext analysers have been developed commercially to produce sufficient views of the teletext to prove that the service provided is transmitted in the way intended. The dynamic allocation equipment has also made it easier to reconfigure the VBI to accommodate new services such as Audio Description and other developments in teletext