Systems and methods for measuring interest levels of audience in a broadcast program and providing extra information based on the interest level. The methods include receiving an AV signal of a broadcast program and supplementary content which contains broadcast program related information and a tag identifying the broadcast program. The supplementary content is combined with the AV signal to form a data-augmented signal which is subsequently modulated with a carrier signal to form a transmit signal for broadcasting to receivers. Each receiver includes a decoder for extracting the supplementary content and means for computing interest levels and providing extra information based on the interest levels. (Fig. 5A)
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