Methods and apparatus to perform audio watermarking and watermark detection and extraction
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.
1. An encoder apparatus comprising:
at least one memory;
instructions; and
processor circuitry to execute the instructions to:
access audio samples to be encoded with one or more data symbols;
select a first look up table (LUT) from a plurality of LUTs in response to a determination that that the audio samples were not previously encoded, the plurality of LUTs to specify respective different mappings of code frequencies to symbol values;
select a second LUT from the plurality of LUTs in response to a determination that that the audio samples were previously encoded;
map the one or more data symbols to code frequencies based on the selected one of the first LUT or the second LUT; and
combine the code frequencies and the audio samples to encode the audio samples with the one or more data symbols.
2. The apparatus of claim 1 , wherein the one or more data symbols correspond to a communication message when the audio samples were not previously encoded, and the one or more data symbols correspond to pre-existing code flag information when the audio samples were previously encoded.
3. The apparatus of claim 2 , wherein the communication message includes a synchronization portion and one or more portions including data bits.
4. The apparatus of claim 2 , wherein the processor circuitry is to select the first LUT from the plurality of LUTs based on a synchronization symbol of the communication message.
5. The apparatus of claim 1 , wherein the processor circuitry is to synthesize the code frequencies at amplitudes according to a masking evaluation.
6. The apparatus of claim 5 , wherein prior to the code frequencies being synthesized, the processor circuitry is to conduct the masking evaluation to determine a threshold amplitude at which the code frequencies are to be generated to remain inaudible or substantially inaudible to a human.
7. The apparatus of claim 6 , wherein to perform the masking evaluation, the processor circuitry is to:
generate overlapping short blocks of the audio samples; and
perform masking evaluations on the short blocks.
8. A non-transitory computer readable medium comprising instructions that, when executed, cause processor circuitry to at least:
access audio samples to be encoded with one or more data symbols;
select a first look up table (LUT) from a plurality of LUTs in response to a determination that that the audio samples were not previously encoded, the plurality of LUTs to specify respective different mappings of code frequencies to symbol values;
select a second LUT from the plurality of LUTs in response to a determination that that the audio samples were previously encoded;
map the one or more data symbols to code frequencies based on the selected one of the first LUT or the second LUT; and
combine the code frequencies and the audio samples to encode the audio samples with the one or more data symbols.
9. The non-transitory computer readable medium of claim 8 , wherein the one or more data symbols correspond to a communication message when the audio samples were not previously encoded, and the one or more data symbols correspond to pre-existing code flag information when the audio samples were previously encoded.
10. The non-transitory computer readable medium of claim 9 , wherein the communication message includes a synchronization portion and one or more portions including data bits.
11. The non-transitory computer readable medium of claim 9 , wherein the instructions, when executed, cause the processor circuitry to select of the first LUT from the plurality of LUTs based on a synchronization symbol of the communication message.
12. The non-transitory computer readable medium of claim 9 , wherein the instructions, when executed, cause the processor circuitry to synthesize the code frequencies at amplitudes according to a masking evaluation.
13. The non-transitory computer readable medium of claim 12 , wherein prior to the code frequencies being synthesized, the instructions, when executed, cause the processor circuitry to conduct the masking evaluation to determine a threshold amplitude at which the code frequencies are to be generated to remain inaudible or substantially inaudible to a human.
14. The non-transitory computer readable medium of claim 13 , wherein to perform the masking evaluation, the instructions, when executed, cause the processor circuitry to:
generate overlapping short blocks of the audio samples; and
perform masking evaluations on the short blocks.
15. A method comprising:
accessing audio samples to be encoded with one or more data symbols;
selecting a first look up table (LUT) from a plurality of LUTs in response to a determination that that the audio samples were not previously encoded, the plurality of LUTs to specify respective different mappings of code frequencies to symbol values;
selecting a second LUT from the plurality of LUTs in response to a determination that that the audio samples were previously encoded;
mapping the one or more data symbols to code frequencies based on the selected one of the first LUT or the second LUT; and
combining the code frequencies and the audio samples to encode the audio samples with the one or more data symbols.
16. The method of claim 15 , wherein the one or more data symbols correspond to a communication message when the audio samples were not previously encoded, and the one or more data symbols correspond to pre-existing code flag information when the audio samples were previously encoded.
17. The method of claim 16 , further including selecting the first LUT from the plurality of LUTs based on a synchronization symbol of the communication message.
18. The method of claim 15 , further including synthesizing the code frequencies at amplitudes according to a masking evaluation.
19. The method of claim 18 , wherein prior to the code frequencies being synthesized, further including conducting the masking evaluation to determine a threshold amplitude at which the code frequencies are to be generated to remain inaudible or substantially inaudible to a human.
20. The method of claim 19 , wherein performing the masking evaluation includes:
generating overlapping short blocks of the audio samples; and
performing masking evaluations on the short blocks.