Abstract: According to the present invention there is provided a method of analysis of the audience for channels selectable by a channel selector device for presentation on a presentation device, the channel selector device providing data indicating which channels are selected and the lengths of time for which selected channels remain selected. The data relating to the lengths of time for which channels remain selected is subject to a capping procedure, whereby the indicated length of time for which a channel remains selected is reduced to a capped maximum permitted length of time if the indicated length of time exceeds the maximum permitted length, to provide capped data.

Abstract: Aspects of the invention relate to an audio matching system for detecting matching of audio signals. In one embodiment, the system comprises a digital signature generation device configured to generate signatures from an audio signal. The device may comprise a signal energy analyser, an event detector, a signature generator, and a transmitter. Embodiments may further include an audio signal comparing device that comprises a receiver, an event locator arranged to use the event data of the received digital signature to locate corresponding portions of another sampled data segment of another audio signal, and an event analyser arranged to analyse the corresponding portions located by the event locator and to determine whether they match the predetermined events of the event data, to thereby determine whether the audio signals match.

Abstract: Audience measurement systems having fixed and portable monitoring devices are provided. Embodiments of the audience measurement system may be suitable for monitoring programs viewed and/or listened to by one or more members of a sample household. The fixed monitoring device may be associated with a particular media device, for example, in the household's home and monitor a received broadcast signal and/or a state of the media device to extract information enabling a received program and/or station to be identified. The portable monitoring device may comprise a receiver for receiving sound of a program emitted by any nearby media device; a data extractor for extracting data from the received sound to enable a program and/or station to be identified. Either a first or a second communicator may be operable to transmit a device present signal in the vicinity of its respective monitoring device, and/or detect the said signal.

Abstract: Method and apparatus for generating a digital signature are provided. The method comprises:—polarizing a sampled data segment, for example a sampled audio segment, to produce a two-state signal having a bit sequence providing a binary representation of the sampled data segment, detecting an event in the signal, the event corresponding to occurrence of a predetermined pattern in the bit sequence of the signal, selecting, on the basis of a predetermined signature collection pattern specifying a plurality of offsets from the detected event, the values of the respective bits of the bit sequence at the bit positions specified by the offsets, and on the basis of those values providing a digital signature characteristic of the sampled data segment. Related systems are also provided.