Methods and apparatus for increasing the robustness of media signatures

1. An apparatus to enhance characteristics of an audio signal, the apparatus comprising:

a characteristic analyzer to determine a first difference between (A) a first characteristic of an audio signal at a first time and (B) a second characteristic of the audio signal at a second time; and

a characteristic enhancer to:

compare the first difference to a first threshold;

at least one of (A) boost the first characteristic of the audio signal at the first time or (B) attenuate the second characteristic of the audio signal at the second time when the first difference does not satisfy the threshold to create an enhanced audio signal; and

determine whether a second difference between a third characteristic of the enhanced audio signal at the first time and a fourth characteristic of the enhanced audio signal at the second time satisfies the threshold, the third characteristic corresponding to the first characteristic, the fourth characteristic corresponding to the second characteristic.

2. The apparatus of claim 1 , further including a transmitter to transmit the enhanced audio signal to a media output device.

3. The apparatus of claim 1 , wherein the first time is the second time.

4. The apparatus of claim 1 , wherein the characteristic enhancer is to provide the enhanced audio signal to an output of a media output device.

5. The apparatus of claim 1 , wherein:

the first characteristic of the audio signal is at least one of a first energy of a first frequency band of the audio signal at the first time, a first energy of the audio signal at the first time, a first discrete cosine transform coefficient, or a first peak frequency at the first time; and

the second characteristic of the audio signal is at least one of a second energy of a second frequency band of the audio signal at the second time, a second energy of the audio signal at the second time, a second discrete cosine transform coefficient, or a second peak frequency at the second time.

6. The apparatus of claim 1 , wherein the characteristic enhancer is to limit adjustment of at least one of the first characteristic or the second characteristic to avoid at least one of audible distortion, violation of media requirements, or a negative effect on a subsequent comparison.

7. The apparatus of claim 1 , wherein the characteristic analyzer is to determine the first characteristic of the audio signal at the first time and the second characteristic of the audio signal at the second time based on a signature algorithm.

8. The apparatus of claim 7 , further including a signature settings determiner to select the signature algorithm from a plurality of signature algorithms.

9. The apparatus of claim 1 , wherein the characteristic enhancer is to at least one of (A) boost the first characteristic of the audio signal at the first time or (B) attenuate the second characteristic of the audio signal at the second time to increase the second difference between the third characteristic of the enhanced audio signal at the first time and the fourth characteristic of the enhanced audio signal at the second time.

10. A non-transitory computer readable storage medium comprising instructions which, when executed, cause a machine to at least:

determine a first difference between (A) a first characteristic of an audio signal at a first time and (B) a second characteristic of the audio signal at a second time;

compare the first difference to a first threshold;

at least one of (A) boost the first characteristic of the audio signal at the first time or (B) attenuate the second characteristic of the audio signal at the second time when the first difference does not satisfy the threshold to create an enhanced audio signal; and

determine whether a second difference between a third characteristic of the enhanced audio signal at the first time and a fourth characteristic of the enhanced audio signal at the second time satisfies the threshold, the third characteristic corresponding to the first characteristic, the fourth characteristic corresponding to the second characteristic.

11. The computer readable storage medium of claim 10 , wherein the instructions cause the machine to transmit the enhanced audio signal to a media output device.

12. The computer readable storage medium of claim 10 , wherein the first time is the second time.

13. The computer readable storage medium of claim 10 , wherein the instructions cause the machine to provide the enhanced audio signal to an output of a media output device.

14. The computer readable storage medium of claim 10 , wherein:

the first characteristic of the audio signal is at least one of a first energy of a first frequency band of the audio signal at the first time, a first energy of the audio signal at the first time, a first discrete cosine transform coefficient, or a first peak frequency at the first time; and

the second characteristic of the audio signal is at least one of a second energy of a second frequency band of the audio signal at the second time, a second energy of the audio signal at the second time, a second discrete cosine transform coefficient, or a second peak frequency at the second time.

15. The computer readable storage medium of claim 10 , wherein the instructions cause the machine to limit adjustment of at least one of the first characteristic or the second characteristic to avoid at least one of audible distortion, violation of media requirements, or a negative effect on a subsequent comparison.

16. The computer readable storage medium of claim 10 , wherein the instructions cause the machine to determine the first characteristic of the audio signal at the first time and the second characteristic of the audio signal at the second time based on a signature algorithm.

17. The computer readable storage medium of claim 16 , wherein the instructions cause the machine to select the signature algorithm from a plurality of signature algorithms.

18. The computer readable storage medium of claim 10 , wherein the instructions cause the machine to at least one of (A) boost the first characteristic of the audio signal at the first time or (B) attenuate the second characteristic of the audio signal at the second time to increase the second difference between the third characteristic of the enhanced audio signal at the first time and the fourth characteristic of the enhanced audio signal at the second time.

19. An method to enhance characteristics of an audio signal, the method comprising:

determining a first difference between (A) a first characteristic of an audio signal at a first time and (B) a second characteristic of the audio signal at a second time;

comparing, by executing an instruction with a processor the first difference to a first threshold;

at least one of (A) boosting, by executing an instruction with the processor, the first characteristic of the audio signal at the first time or (B) attenuating, by executing an instruction withe the processor the second characteristic of the audio signal at the second time when the first difference does not satisfy the threshold to create an enhanced audio signal; and

determining, by executing an instruction with the processor, whether a second difference between a third characteristic of the enhanced audio signal at the first time and a fourth characteristic of the enhanced audio signal at the second time satisfies the threshold, the third characteristic corresponding to the first characteristic, the fourth characteristic corresponding to the second characteristic.

20. The method of claim 19 , further including transmitting the enhanced audio signal to a media output device.