Methods and apparatus to identify signals using a low power watermark

1. An apparatus for media identification based on watermarks, the apparatus comprising:

a first processor to:

determine, in response to receiving a signal, if a first watermark is present in the signal using a first processing technique, the first processing technique including:

compare a filtered watermark signal to a reference watermark signal corresponding to a universal watermark;

output an error value, wherein the error value is a difference between the filtered watermark signal and the reference watermark signal, the error value indicative of whether the first watermark is present in the signal; and

in response to the error value satisfying a threshold, reduce the error value associated with a frequency by adjusting coefficients in a direction opposite of a corresponding amplitude to the error value at the frequency;

provoke, in response to the first watermark being present in the signal, a second processing technique on a signal processor; and

the signal processor to:

extract a second watermark in the signal using the second processing technique.

2. The apparatus of claim 1 , wherein the first processing technique requires less processing power than the second processing technique.

3. The apparatus of claim 1 , wherein the first watermark is a universal watermark that has same characteristics among multiple signals associated with media presentations.

4. The apparatus of claim 3 , wherein the universal watermark has a length corresponding to a length of the second watermark, wherein the second watermark is a media identification watermark.

5. The apparatus of claim 1 , wherein the signal processor is in a low power mode when the first watermark is not present.

6. The apparatus of claim 1 , wherein the first processor is further to alter the signal processor from a low power state to a high power state in response to determining the first watermark to be present.

7. The apparatus of claim 1 , wherein the second watermark is an identification watermark pertaining to the media represented by the signal.

8. The apparatus of claim 1 , wherein the first processing technique includes a least means square adaptive algorithm.

9. The apparatus of claim 8 , wherein the first processing technique includes filtering the signal using a linear filter, to generate the filtered watermark signal.

10. The apparatus of claim 9 , wherein the first processing technique includes an adaptive algorithm, the adaptive algorithm to adjust coefficients associated with the linear filter based on the error value calculated when comparing the filtered watermark signal to the reference watermark signal.

11. A non-transitory computer readable storage medium comprising

instructions which, when executed, cause a machine to at least:

determine, in response to receiving a signal, if a first watermark is present in the signal using a first processing technique, the first processing technique including:

compare a filtered watermark signal to a reference watermark signal corresponding to a universal watermark;

output an error value, wherein the error value is a difference between the filtered watermark signal and the reference watermark signal, the error value indicative of whether the first watermark is present in the signal; and

in response to the error value satisfying a threshold, reduce the error value associated with a frequency by adjusting coefficients in a direction opposite of a corresponding amplitude to the error value at the frequency;

provoke, in response to the first watermark being present in the signal, a second processing technique on a signal processor; and

extract a second watermark in the signal using the second processing technique.

12. The non-transitory computer readable storage medium of claim 11 , wherein the instructions, when executed, further cause the machine to alter the signal processor from a lower power state to a high power state in response to determining the first watermark to be present.

13. The non-transitory computer readable storage medium of claim 11 , wherein the first processing technique requires less processing power than the second processing technique.

14. The non-transitory computer readable storage medium of claim 11 , wherein the first watermark has a length corresponding to a length of the second watermark, wherein the first watermark is a universal watermark that has same characteristics among multiple signals and the second watermark is a media identification watermark.

15. A method comprising:

determining, in response to receiving a signal, if a first watermark is present in the signal using a first processing technique, the first processing technique including:

comparing a filtered watermark signal to a reference watermark signal corresponding to a universal watermark;

outputting an error value, wherein the error value is a difference between the filtered watermark signal and the reference watermark signal, the error value indicative of whether the first watermark is present in the signal; and

in response to the error value satisfying a threshold, reducing the error value associated with a frequency by adjusting coefficients in a direction opposite of a corresponding amplitude to the error value at the frequency;

provoking, in response to the first watermark being present in the signal, a second processing technique; and

extracting a second watermark in the signal using the second processing technique.

16. The method of claim 15 further including altering a signal processor from a low power state to a high power state in response to determining the first watermark to be present.

17. The method of claim 15 , wherein the first processing technique consumes less processing resources than the second processing technique.

18. The method of claim 15 , wherein the first watermark is a universal watermark that has same characteristics among multiple signals.

19. The method of claim 15 , wherein the second watermark is a media identification watermark.