| 摘要 |
A method for controlling presentation of items of enhanced content in an interactive television system comprising at least one distribution unit and a plurality of decoder units arranged to store items of enhanced content and cause them to be presented to a user on receipt of a trigger signal from the distribution unit, the method comprising: storing the items of enhanced content at the decoder units; storing at the distribution unit a schedule indicating a desired synchronisation between the items of enhanced content and a running program with which the enhanced content is associated, the running program comprising a timing stream and a series of periodic indications of the identity of the running program; transmitting the running program to the decoder units over a transmission channel via the distribution unit; and at the distribution unit analysing traffic passing over the transmission channel so as to determine whether the said periodic indications of the identity of the running program continue to be detected as passing over the transmission channel, and generating trigger signals in respect of the enhanced content associated with the running program only whilst it is determined that the said periodic indications continue to be detected as passing over the transmission channel. <IMAGE>
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