Methods and apparatus to determine a state of a media presentation device
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.
1. An apparatus to determine a source of a first audio signal sensed by a first microphone, the apparatus comprising:
memory to store instructions; and
at least one processor to execute the instructions to at least:
compare the first audio signal to a second audio signal from a second microphone to generate a first set of weighted coefficients, the first microphone and the second microphone positioned with respect to a first source;
compare the first set of weighted coefficients to a second set of weighted coefficients of a reference audio signal to generate a similarity value, the reference audio signal based on audio sensed by the first microphone and by the second microphone and originated from the first source; and
identify the source of the first audio signal as the first source in response to the similarity value satisfying a threshold.
2. The apparatus of claim 1 , wherein the at least one processor is further to control a metering device associated with the first source to capture media exposure data from the first source in response to the at least one processor identifying the source of the first audio signal as the first source.
3. The apparatus of claim 2 , wherein the media exposure data includes a watermark extracted from the first audio signal.
4. The apparatus of claim 1 , wherein the at least one processor is to compare the first set of weighted coefficients and the second set of weighted coefficients to generate the similarity value by calculating a dot product between the first set of weighted coefficients and the second set of weighted coefficients.
5. The apparatus of claim 1 , wherein the at least one processor is further to:
generate an error signal based on a comparison of the second set of weighted coefficients to a third set of weighted coefficients of an updated reference signal originating from the first source; and
replace the second set of weighted coefficients with the third set of weighted coefficients when the error signal exceeds an error threshold.
6. The apparatus of claim 5 , wherein the at least one processor is to generate the error signal according to X e (n)=X d (n)−Y 0 (n), the X d (n) representing an audio sample and the Y 0 (n) representing a summed filter output of multiple audio samples, the n being an iteration index, and the at least one processor to work with a weight adjuster to adjust the first set of weighted coefficients based on the error signal according to W m (n+1)=W m (n)+μX e X m (n), the W m (n+1) and the W m being weight coefficients, X m (n) being a weighted audio sample, and the μ being a learning factor.
7. The apparatus of claim 1 , wherein the at least one processor is to generate the first and second sets of weighted coefficients with an adaptive echo cancellation algorithm implemented with a finite impulse response filter.
8. The apparatus of claim 1 , wherein the at least one processor is to filter one of the first audio signal or the second audio signal for comparison to another of the first audio signal or the second audio signal.
9. A computer readable storage medium comprising instructions that, when executed, cause a machine to at least:
compare a first audio signal from a first microphone to second audio from a second microphone to generate a first set of weighted coefficients, the first microphone and the second microphone positioned with respect to a first source;
compare the first set of weighted coefficients to a second set of weighted coefficients of a reference audio signal to generate a similarity value, the reference audio signal based on audio originated from the first source; and
identify the source of the first audio signal as the first source when the similarity value satisfies a threshold.
10. The computer readable storage medium of claim 9 , wherein the instructions, when executed, further cause the machine to control a metering device associated with the first source to capture media exposure data from the first source in response to identifying the source of the first audio signal as the first source.
11. The computer readable storage medium of claim 9 , wherein the instructions, when executed, cause the machine to compare the first set of weighted coefficients and the second set of weighted coefficients to generate the similarity value by calculating a dot product between the first set of weighted coefficients and the second set of weighted coefficients to generate the similarity value.
12. The computer readable storage medium of claim 9 , wherein the instructions, when executed, cause the machine to:
generate an error signal based on a comparison of the second set of weighted coefficients to a third set of weighted coefficients of an updated reference signal originating from the first source; and
replace, when the error signal exceeds an error threshold, the second set of weighted coefficients with the third set of weighted coefficients for comparison to the first set of weighted coefficients for the first audio signal.
13. The computer readable storage medium of claim 12 , wherein the instructions, when executed, cause the machine to generate the error signal by generating the error signal, X e (n), according to X e (n)=X d (n)−Y 0 (n), the X d (n) representing an audio sample and the Y 0 (n) representing a summed filter output of multiple audio samples, the n being an iteration index, and the first set of weighted coefficients to be adjusted based on the error signal according to to W m (n+1)=W m (n)+μX e X m (n), the W m (n+1) and the W m being weight coefficients, X m (n) being a weighted audio sample, and the μ being a learning factor.
14. The computer readable storage medium of claim 9 , wherein the instructions, when executed, cause the machine to generate the first and second sets of weighted coefficients based on an adaptive echo cancellation algorithm applied by a finite impulse response filter.
15. The computer readable storage medium of claim 9 , wherein the instructions, when executed, cause the machine to filter one of the first audio signal or the second audio for comparison to another of the first audio signal or the second audio.
16. An apparatus to determine a source of a first audio signal sensed by a first microphone, the apparatus comprising:
means for comparing the first audio signal to a second audio signal from a second microphone to generate a first set of weighted coefficients, the first microphone and the second microphone positioned with respect to a first source; and
means for comparing the first set of weighted coefficients to a second set of weighted coefficients of a reference audio signal to generate a similarity value, the reference audio signal based on audio sensed by the first microphone and by the second microphone and originated from the first source; and
means for identifying the source of the first audio signal as the first source in response to the similarity value satisfying a threshold.
17. The apparatus of claim 16 , further including means for controlling a metering device associated with the first source to capture media exposure data from the first source in response to identifying the source of the first audio signal as the first source.
18. The apparatus of claim 16 , further including means for generating an error signal based on a comparison of the second set of weighted coefficients to a third set of weighted coefficients of an updated reference signal originating from the first source and replacing the second set of weighted coefficients with the third set of weighted coefficients when the error signal exceeds an error threshold.
19. The apparatus of claim 18 , further including means to adjust weights applied to at least one of the first set of weighted coefficients or the second set of weighted coefficients based on the error signal.
20. The apparatus of claim 16 , further including means for filtering one of the first audio signal or the second audio signal for comparison to another of the first audio signal or the second audio signal.