| 摘要 |
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.
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