Multiple-source transmission system

摘要

An advertisement insertion system arranged to substitute a local advertisement in place of a national advertisement arriving over a national television feed signal for community television. The system includes a compressed digital source for storing the local advertisement as well as a signal processor which has as inputs both the national television feed signal and the digital source. The national television signal includes a standard television signal and a cue tone which is used to select the data from the digital source for delivery to the signal processor. The signal processor generates a timing signal from the vertical synchronization signal of the standard television signal, and also converts the selected data to an alternative television signal synchronized to the national television signal. The signal transmitted by the signal processor, in response to the cue tone, is either the national television signal or the alternative television signal. The signal processor controls the flow of data from the digital source so the selected data is available to reconstruct the alternative television signal as needed.