Methods and apparatus to monitor audio/visual content from various sources are disclosed. An example method disclosed herein comprises determining first information based on a video signal corresponding to monitored media content, determining second information based on an audio signal corresponding to the monitored media content, and identifying a selected one of a plurality of media content sources based on a decision tree comprising a plurality of decision nodes, a first decision node of the decision tree corresponding to a first classification decision resulting from processing at least one of the first information or second information, and a second decision node of the decision tree corresponding to a second classification decision resulting from processing at least one of the first information or second information, the second decision node of the decision tree being selected for evaluation based on an outcome of evaluating the first decision node of the decision tree.