Methods and apparatus to monitor audio/visual content from various sources

摘要

Methods and apparatus to monitor audio/visual content from various sources are disclosed. Example methods disclosed herein to monitor a media presentation can include counting zero crossings associated with a plurality of audio samples of an audio signal corresponding to the media presentation, and determining whether the audio signal is muted based on whether a number of zero crossings satisfies a first threshold. Such example methods can also include, when the audio signal is determined to not be muted, determining a source of the media presentation based on whether the audio signal is determined to be compressed.

主权项

1. A method to monitor a media presentation, the method comprising:
counting zero crossings associated with a plurality of audio samples of an audio signal corresponding to the media presentation; determining whether the audio signal is muted based on whether a number of zero crossings satisfies a first threshold; and when the audio signal is determined to not be muted:
generating a plurality of transform coefficients associated with the plurality of audio samples;examining a subset of the plurality of transform coefficients corresponding to a frequency range exceeding a threshold frequency;determining whether the audio signal is compressed based on a number of transform coefficients substantially equal to zero in the subset of the plurality of transform coefficients; anddetermining a source of the media presentation based on whether the audio signal is determined to be compressed.