| 摘要 |
A receiver for an enhanced television system in which video data defining a video stream, enhanced content data defining items of enhanced content, and trigger messages for triggering the play-out of the enhanced content are transmitted to receivers over a data network, the receiver comprising an enhanced content decoder for receiving and playing out enhanced content, and the enhanced content decoder including a cache for caching enhanced content data received from the network; and a play-out controller for controlling the play-out of enhanced content, the play-out controller being arranged to receive trigger messages over the network and on receiving a trigger message that indicates an item of enhanced content for which enhanced content data is stored in the cache and that is to be played out, to play out that item of enhanced content data at a time indicated by the trigger message, and on receiving a trigger message that includes a definition of enhanced content, to play out the enhanced content defined in the trigger message at a time indicated by the trigger message.
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