| 摘要 |
PURPOSE: The protocol and system are provided for transmitting triggers from a remote network and for controlling interactive program content at a broadcast station. CONSTITUTION: The device relates to an interactive television system and to the inserting of interactive program in the television signal produced. A digital broadcast station is configured to turn around and add interactive programming to a television signal originally conveyed by a remote network. The remote network inserts trigger commands within the vertical blanking intervals (VBIs) of the television signal to control the loading and playing of the interactive program at the broadcast station. The protocol associated with the trigger commands allows commands to be repeated to thereby ensure that the interactive program is controlled correctly, even in the event that an original command was not received or was corrupted in the transmission. If a repeated trigger command is received by the broadcast station and the original command was not properly received, the interactive program source enters an error recovery state to determine the appropriate action for the interactive program source. For certain commands, such as continue,pause and stop, the interactive program source responds to the repeated command without further error compensation. For other commands, such as a command to play a specified file at a particular time, an error recovery mechanism compares the time code associated with the command with the local time and indexes into the specified file at a point which compensates for the difference between the particular time indicated by the command and the actual time for playing.
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