Abstract: A television broadcasting system is described in which a transmission unit controls the presentation of items of enhanced content during a running program. The presentation of the items of enhanced content is triggered in response to receipt by the transmission unit of periodic indications embedded in the running program. For each periodic indication, a criterion indicative of the quality of that periodic indication is measured and stored by the transmission unit as quality data. During the running program, if no indication is received by the transmission unit for a predetermined time, the transmission unit accesses the quality data to determine an expected indication quality. If the expected indication quality is above a threshold quality level, the triggering of enhanced content is suspended. On the other hand, if the expected indication quality is below the threshold, the presentation of enhanced content continues to be triggered.

Abstract: A media playout system for playing out media to receiver units, the system comprising: a broadcast data channel; a playout arrangement for broadcasting over the broadcast data channel enhanced content data associated with video data; a distribution unit for receiving the broadcast data and distributing it to the receiver units, and comprising a buffer for storing enhanced content data, and a transmission controller responsive to signalling from the playout arrangement to retrieve enhanced content data from the buffer and make it available to the receiver units.

Abstract: A method for controlling transmission of messages in an interactive television system comprising a network and a plurality of receiver units connected to the network; the method comprising: transmitting to the receiver units an trigger inviting a response from each receiver unit and indicating that a delay procedure is to be applied to the responses; and at each receiver unit: accepting from a user of the receiver unit data in response to the trigger; forming a response message for transmission to the network in response to the trigger, the response message including the data received from the user; determining the length of a delay interval to be applied to the response message; and transmitting the response message to the network after the delay.

Abstract: A signal formatting apparatus for use in a television transmission system, the apparatus comprising: an enhanced content input for receiving enhanced content streams in a predefined input format; a plurality of enhanced content outputs for outputting enhanced content data in a plurality of formats for transmission to receivers of respective types; and a signal formatter for forming the enhanced content data by processing the enhanced content streams to put each of the enhanced content streams in the respective format.

Abstract: 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 de