Methods and apparatus to perform audio watermarking and watermark detection and extraction
Methods and apparatus to perform audio watermarking and watermark detection and extraction are disclosed. Example apparatus include means for transforming an audio signal into a frequency domain representation, and means for determining characteristics of frequencies of the frequency domain representation that may contain the code. In some examples, the means for determining is to normalize the characteristics of the frequencies of the frequency domain representation in respective ones of the code bands that may contain the code to determine normalized characteristics of the frequencies representative of the code, a respective one of the code bands that may contain the code to be normalized against a first characteristic of a first frequency in that code band; sum the normalized characteristics of the frequencies representative of the code; determine the sum is representative of the code when the sum satisfies a threshold; and validate the code based on an encoding scheme.
1. An apparatus to decode an audio signal to obtain a code, the code encoded in the audio signal with a plurality of frequency components in a plurality of code bands, the apparatus comprising:
means for transforming the audio signal into a frequency domain representation; and
means for determining characteristics of frequencies of the frequency domain representation that may contain the code, the means for determining to:
normalize the characteristics of the frequencies of the frequency domain representation in respective ones of the code bands that may contain the code to determine normalized characteristics of the frequencies representative of the code, a respective one of the code bands that may contain the code to be normalized against a first characteristic of a first frequency in that code band;
sum the normalized characteristics of the frequencies representative of the code to determine a sum for the frequencies representative of the code;
determine that the sum is representative of the code when the sum satisfies a threshold; and
validate the code based on an encoding scheme.
2. The apparatus of claim 1 , wherein different sets of the frequency components represent respectively different information, one frequency component from each of the sets of the frequency components is located in a code band, there are multiple code bands, and spacing between adjacent code bands is equal to or less than the spacing between adjacent frequency components of each code band.
3. The apparatus of claim 2 , wherein the characteristics of the frequencies that may contain the code are amplitudes of the frequencies.
4. The apparatus of claim 2 , wherein the characteristics of the frequencies that may contain the code are energies of the frequencies.
5. The apparatus of claim 1 , wherein the means for determining is to reduce a number of frequencies processed after the code is determined.
6. The apparatus of claim 5 , wherein the code includes synchronization information.
7. The apparatus of claim 1 , wherein the first characteristic is a magnitude of a frequency component having the highest energy in that code band.
8. An apparatus to decode an audio signal to obtain a code, the code encoded in the audio signal with a plurality of frequency components in a plurality of code bands, the apparatus comprising:
a memory; and
a processor to execute instructions stored in the memory to at least:
transform the audio signal into a frequency domain representation;
determine characteristics of frequencies of the frequency domain representation that may contain the code;
normalize the characteristics of the frequencies of the frequency domain representation in respective ones of the plurality of code bands that may contain the code to determine normalized characteristics of the frequencies representative of the code, a respective one of the code bands that may contain the code to be normalized against a first characteristic of a first frequency in that code band;
sum the normalized characteristics of the frequencies representative of the code to determine a sum for the frequencies representative of the code;
determine that the sum is representative of the code when the sum satisfies a threshold; and
validate the code based on an encoding scheme.
9. The apparatus of claim 8 , wherein different sets of the frequency components represent respectively different information, one frequency component from each of the sets of the frequency components is located in a code band, there are multiple code bands, and spacing between adjacent code bands is equal to or less than the spacing between adjacent frequency components of each code band.
10. The apparatus of claim 9 , wherein the characteristics of the frequencies that may contain the code are amplitudes of the frequencies.
11. The apparatus of claim 9 , wherein the characteristics of the frequencies that may contain the code are energies of the frequencies.
12. The apparatus of claim 8 , wherein the processor is to reduce a number of frequencies processed after the code is determined.
13. The apparatus of claim 12 , wherein the code includes synchronization information.
14. A system to decode an audio signal, the system comprising:
a receiver to receive the audio signal;
a converter to transform the encoded audio signal into a frequency domain representation; and
a monitor to:
determine characteristics of frequencies of the frequency domain representation that may contain the code;
normalize the characteristics of the frequencies of the frequency domain representation in respective ones of the code bands that may contain the code to determine normalized characteristics of the frequencies representative of the code, a respective one of the code bands that may contain the code to be normalized against a first characteristic of a first frequency in that code band;
sum the normalized characteristics of the frequencies representative of the code to determine a sum for the frequencies representative of the code;
determine that the sum is representative of the code when the sum satisfies a threshold; and
validate the code based on an encoding scheme.
15. The system of claim 14 , wherein different sets of the frequency components represent respectively different information, one frequency component from each of the sets of the frequency components is located in a code band, there are multiple code bands, and spacing between adjacent code bands is equal to or less than the spacing between adjacent frequency components of each code band.
16. The system of claim 15 , wherein the characteristics of the frequencies that may contain the code are amplitudes of the frequencies.
17. The system of claim 15 , wherein the characteristics of the frequencies that may contain the code are energies of the frequencies.
18. The system of claim 14 , wherein the monitor is to reduce a number of frequencies processed after the code is determined.
19. The system of claim 18 , wherein the code includes synchronization information.
20. The system of claim 14 , wherein the first characteristic is a magnitude of a frequency component having the highest energy in that code band.