Abstract: To accurately detect the channel being actually selected by a TV having built therein a digital tuner, a terminal device connected to the TV analyzes the preamble of a digital audio signal from the TV to thereby detect a change of audio data-type, and for each viewing period from the time of the change of audio data-type to the time of the next change of audio data-type, generates viewing block data containing comparison feature data extracted from data-bursts within the viewing period concerned and time data of the viewing period concerned, and transmits the generated viewing block data to a center apparatus. The center apparatus identifies, for each viewing block, the actually selected channel by making a comparison between the comparison feature data contained in the viewing block data received from the terminal device and reference feature data contained reference data of each channel stored in the reference data storage part.

Abstract: To identify the channel being actually selected by a TV set having built therein a digital tuner, a meter, which forms a channel selecting status monitoring apparatus, is connected via a cable to a digital audio output terminal of the TV set that outputs a digital audio signal of the selected channel. A digital audio signal comparison part checks whether the contents of a payload of a data-burst generated from the digital audio signal output from the digital audio output terminal coincides with the contents of a payload of a data-burst generated from a digital audio signal from a reference tuner, taking into consideration delays of the both digital audio signals on the time base.

Abstract: A monitoring apparatus (3) which is used to monitor the channel actually selected by a TV set (1). A reference tuner (32) independently reproduces and output an audio signal of the channel to be monitored. An audio comparison part (31) compares the feature parameter of an audio signal from a loudspeaker output terminal (13) of the TV set and the feature parameter of the audio signal from the reference tuner to detect whether or not the both signals coincide with each other. A remote control signal receiving part (34) receives a signal from a TV remote control signal transmitter (2) to obtain information of a channel to be switched to. At the time of changing the channel of the reference tuner until coincidence is detected in the audio comparison part, a control part (37) indicates first to the reference tuner the channel to be switched to identified by the remote control signal part, thereby permitting fast and accurate monitoring of the channel being selected by the TV set.