METHODS AND APPARATUS TO MONITOR AUDIO/VISUAL CONTENT FROM VARIOUS SOURCES

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.