Abstract: Methods, apparatus, systems and articles of manufacture to reduce signature matching uncertainty in media monitoring systems are disclosed. Disclosed example apparatus are to compare first groups of monitored signatures representative of monitored media with second groups of reference signatures representative of respective reference media to determine a first sequence of match results for an observation period, the first and second groups to have a first size corresponding to a first number of signatures. Disclosed example apparatus are also to compare, in response to a discontinuity in the first sequence of signature match results, third groups of monitored signatures from the sequence of monitored signatures with fourth groups of reference signatures from the respective sequences of reference signatures to determine a second sequence of signature match results for the observation period, the third groups and the fourth groups to have a second size greater than the first size.

Abstract: Methods, apparatus, systems and articles of manufacture (e.g., physical storage media) to detect media watermarks in magnetic field data are disclosed herein. Example media monitors disclosed herein include a magnetic field estimator to determine first magnetic field data, the magnetic field estimator in communication with a magnetometer. Disclosed example media monitors also include a correlator to correlate the first magnitude field data with a reference sequence to determine second magnetic field data. Disclosed example media monitors further include a watermark decoder to process the second magnetic field data to detect an audio watermark encoded in an audio signal.

Abstract: A method for generating a signature is disclosed. As part of the method, a first number of bits are identified in respective rows of an audio signature matrix that are determined to be the strongest bits in the row, bits of the audio signature matrix are replaced with respective cells having values depending on whether the respective bits are included in the first number of bits, a set of uniformly distributed numbers are generated within a range of numbered locations corresponding to cells of the audio signature matrix; numerical distances are determined, from respective numbers in the set of uniformly distributed numbers, to the numbered locations of the matrix, associated with nearest occurrences of a first value. A set of integers is generated based on the distances.

Abstract: Example apparatus disclosed herein are to identify encoded information present in audio obtained for a time period. Disclosed example apparatus are also to generate a signature of the audio for comparison with signatures of reference media. Disclosed example apparatus are also to generate a first determination that a media presentation device was in an off state during a first portion of the time period based on a gain level applied by an automatic gain controller to collect the audio. Disclosed example apparatus are also to override the first determination that the media presentation device was in the off state during the first portion of the time period with a second determination that the media presentation device was in an on state during the first portion of the time period, the second determination based on at least one of the encoded information or the signature.

Abstract: Methods and apparatus to perform audio watermarking and watermark detection and extraction are disclosed. Example apparatus disclosed herein are to select frequency components to be used to represent a code, different sets of frequency components to represent respectively different information, respective ones of the frequency components in the sets of frequency components located in respective code bands, there being multiple code bands and spacing between adjacent code bands being equal to or less than the spacing between adjacent frequency components in the code bands. Disclosed example apparatus are also to synthesize the frequency components to be used to represent the code, combine the synthesized frequency components with an audio block of an audio signal, and output the audio signal and a video signal associated with the audio signal.

Abstract: Methods and apparatus for performing variable block length watermarking of media are disclosed. Example apparatus include means for evaluating a masking ability of a first audio block; means selecting a first frequency to represent a first code, the means for selecting to (i) select the first frequency selected from a first set of frequencies that are detectable when performing a frequency transformation using a first block length, but are not detectable when performing a frequency transformation using a second block length, and (ii) select a second frequency to represent a second code, the second frequency selected from a second set of frequencies that are detectable when performing a frequency transformation using the second block length; means for synthesizing a first signal having the first frequency with the masking ability of the first audio block; and means for combining the first signal with the first audio block.

Abstract: Methods and apparatus to count people are disclosed. Example apparatus disclosed herein are to populate a list with first characteristic datasets obtained from a first plurality of images, respective ones of the first characteristic datasets representative of corresponding faces. Disclosed apparatus are also to perform comparisons of the first characteristic datasets to each other to determine a first number of unique faces, the comparisons limited to the first characteristic datasets obtained during the first period of time. Disclosed apparatus are further to delete the first characteristic datasets from the list after the first period of time has ended, and re-populate the list with second characteristic datasets obtained from a second plurality of images representative of the environment during a second period of time of the media presentation, the second period of time subsequent to the first period of time.

Abstract: Methods, apparatus, systems and articles of manufacture are disclosed for scalable architectures for reference signature matching and updating. An example method for scalable architectures for reference signature matching and updating includes accessing site signatures to be compared to reference signatures from a first group of media sources. The example method also include determining if a first reference node is an owner of a first one of the site signatures, comparing a neighborhood of site signatures including the first site signature to reference signatures in a first subset of reference signatures when the first reference node is the owner of the first site signature, the first subset of references signatures stored in a first memory partition associated with the first reference node, and not comparing site signature to reference signatures when the first reference node is not the owner of the first one of the site signatures.

Abstract: An example apparatus includes a first query processor to obtain a first hash key, first qualifier data and first value data associated with the first hash key, the first value data including a second hash key and a third hash key; a candidate qualifier to use the first value data to prequalify the first hash key as a candidate for subsequent signature processing associated with a first site signature, the candidate qualifier to: determine prequalification of the first hash key is successful in response to a determination that the second hash key matches a second site signature preceding the first site signature in time and that the third hash key matches a third site signature following the first site signature in time; and determine the prequalification of the first hash key is unsuccessful in response to a determination that at least one of the second hash key fails to match the second site signature or the third hash key fails to match the third site signature.

Abstract: Example apparatus disclosed herein include a memory and a processor to execute instructions to identify a first set of face rectangles and a second set of face rectangles in a frame pair of image data corresponding to a media environment, the first set of face rectangles corresponding to a first image sensor and the second set of face rectangles corresponding to a second image sensor, remove first face rectangles from the first set of face rectangles and the second set of face rectangles when the first face rectangles are determined to correspond to false positive face detections, group second face rectangles that remain in the first set of face rectangles and the second set of face rectangles after removal of the first face rectangles to form groups of face rectangles, and generate a count of people identified in the media environment based on a number of the groups.

Abstract: Methods and apparatus to analyze microphone placement for watermarks and signatures are disclosed. An example instructions cause one or more processors to at least determine a variance of a magnitude spectrum of a frequency band corresponding to a frequency spectrum of a first audio signal sensed with an audio sensor. The example instructions further cause the one or more processors to determine, based on the variance, a recovery rate associated with at least one of watermark detection or signature generation to be performed on a second audio signal to be sensed with the audio sensor.

Abstract: Example methods and apparatus to audio watermarking and watermark detection and extraction are disclosed herein. An example apparatus disclosed herein includes memory, computer readable instructions, and processor circuitry to execute the computer readable instructions to at least detect a first symbol, a second symbol, a third symbol, and a fourth symbol sequentially in encoded audio samples, determine whether the first symbol is a synchronization symbol, in response to a determination that the first symbol is a synchronization symbol, determine that the first symbol and the third symbol are associated with a first message and the second symbol and the fourth symbol are associated with a second message, and output at least one of the first message or the second message.

Abstract: Methods, apparatus, systems and articles of manufacture to reduce signature matching uncertainty in media monitoring systems are disclosed. Disclosed example apparatus are to compare first groups of monitored signatures representative of monitored media with second groups of reference signatures representative of respective reference media to determine a first sequence of match results for an observation period, the first and second groups to have a first size corresponding to a first number of signatures. Disclosed example apparatus are also to compare, in response to a discontinuity in the first sequence of signature match results, third groups of monitored signatures from the sequence of monitored signatures with fourth groups of reference signatures from the respective sequences of reference signatures to determine a second sequence of signature match results for the observation period, the third groups and the fourth groups to have a second size greater than the first size.

Abstract: Methods and apparatus to determine a state of a media presentation device are disclosed. Example disclosed methods include generating a first set of weighted coefficients based on first audio received by first and second microphones at a first time. Example disclosed methods include generating a second set of weighted coefficients based on second audio received by the first and second microphones at a second time after the first time. Example disclosed methods include comparing the first set of coefficients and the second set of coefficients to generate a similarity value. Example disclosed methods include, when the similarity value satisfies a threshold, determining that the media presentation device is in a first state. Example disclosed methods include, when the similarity value does not satisfy the threshold, determining that the media presentation device is in a second state.

Abstract: Methods, apparatus, systems and articles of manufacture (e.g., physical storage media) to detect media watermarks in magnetic field data are disclosed herein. Example media monitors disclosed herein include a magnetic field estimator to determine first magnetic field data, the magnetic field estimator in communication with a magnetometer. Disclosed example media monitors also include a correlator to correlate the first magnitude field data with a reference sequence to determine second magnetic field data. Disclosed example media monitors further include a watermark decoder to process the second magnetic field data to detect an audio watermark encoded in an audio signal.

Abstract: Methods and apparatus for determining increasing robustness of media signatures are disclosed. An example apparatus disclosed herein is to select to at least one of (A) boost a first characteristic of a media signal at a first time or (B) attenuate a second characteristic of the media signal at a second time based on an effect of the at least one of the boost of the first characteristic or the attenuation of the second characteristic on a difference between a third characteristic of the media signal at a third time and a fourth characteristic of the media signal at a fourth time. The disclosed example apparatus is also to perform the selected one of (A) the boost of the first characteristic of the media signal at the first time or (B) the attenuation of the second characteristic of the media signal at the second time to enhance the media signal.

Abstract: Methods and apparatus to count people are disclosed. Example apparatus disclosed herein are to populate a list with first characteristic datasets obtained from a first plurality of images, respective ones of the first characteristic datasets representative of corresponding faces. Disclosed apparatus are also to perform comparisons of the first characteristic datasets to each other to determine a first number of unique faces, the comparisons limited to the first characteristic datasets obtained during the first period of time. Disclosed apparatus are further to delete the first characteristic datasets from the list after the first period of time has ended, and re-populate the list with second characteristic datasets obtained from a second plurality of images representative of the environment during a second period of time of the media presentation, the second period of time subsequent to the first period of time.

Abstract: Example methods and apparatus to audio watermarking and watermark detection and extraction are disclosed herein. Example methods disclosed herein include determining a first watermark symbol encoded in encoded audio samples and storing the first watermark symbol in tangible memory. Disclosed example methods also include determining a second watermark symbol encoded in the encoded audio samples and storing the second watermark symbol in the tangible memory. Disclosed example methods further include, in response to determining that the first watermark symbol matches the second watermark symbol, outputting the first watermark symbol.

Abstract: Methods, apparatus, systems, and articles of manufacture to perform speed-enhanced playback of recorded media are disclosed. Example apparatus to playback media disclosed herein comprise at least one memory, machine-readable instructions, and processor circuitry to execute the machine-readable instructions to parse an audio frame included in the media to determine a number of skip bytes included in the audio frame, compare the number of skip bytes to a threshold, associate the audio frame with a plurality of candidate frames identified in the media when the number of skip bytes satisfies the threshold, and calculate a speed-enhanced playback rate for the media based on the plurality of candidate frames identified in the media.

Abstract: Methods and apparatus to audio watermarking and watermark detection and extracted are described herein. An example method includes receiving a media content signal, sampling the media content signal to generate samples, storing the samples in a buffer, determining a first sequence of samples in the buffer, determining a second sequence of samples in the buffer, wherein the second sequence of samples is of substantially equal length as the first sequence of samples, calculating an average of the first sequence of samples and the second sequence of samples to generate an average sequence of samples, extracting an identifier from the average sequence of samples, and storing the identifier in a tangible memory.