Multiple scrambled layers for audio watermarking
Apparatus, systems, articles of manufacture, and methods are disclosed for multiple scrambled layers for audio watermarking. An example system includes a scrambler executing instructions to: divide a watermark into a plurality of watermark symbols; map the watermark symbols to a plurality of frequency bins in a plurality of frequency clumps according to a first distribution scheme to create a first watermark layer having a first combination of the frequency bins and a second watermark layer having a second combination of the frequency bins, the first combination of the frequency bins and the second combination of the frequency bins partially overlap. The scrambler also is to determine a sequence for shifting watermark symbols among the frequency bins, and generate a second distribution scheme to map the watermark symbols in accordance with the sequence. The example system also includes a transceiver to communicate the second distribution scheme to a device.
1. A system to map a distribution scheme for encoding an audio signal with a watermark, the system comprising:
a scrambler executing instructions to:
divide the watermark into a plurality of watermark symbols;
map the watermark symbols to a plurality of frequency bins according to a first distribution scheme to create N watermark layers including a first watermark layer having a first combination of the frequency bins and a second watermark layer having a second combination of the frequency bins, the first combination of the frequency bins and the second combination of the frequency bins partially overlap, subsets of adjacent ones of the plurality of frequency bins grouped into a corresponding plurality of frequency clumps;
determine a sequence for shifting watermark symbols between the frequency clumps so that combinations of N watermark symbols that include one watermark symbol from each watermark layer share a maximum of N−1 frequency bins; and
generate a second distribution scheme to map the watermark symbols in accordance with the sequence; and
a transceiver to communicate the second distribution scheme to a device.
2. The system of claim 1 , wherein the sequence includes shifting the watermark symbols of the first watermark layer and the second watermark layer distributed to a first frequency bin in a first frequency clump to a second frequency bin in a second frequency clump to generate the second distribution scheme.
3. The system of claim 2 , wherein the first frequency bin and the second frequency bin are separated by a first distance.
4. The system of claim 3 , wherein the scrambler is to shift the watermark symbols of the first watermark layer and the second watermark layer distributed to a third frequency bin in the first frequency clump to a fourth frequency bin in a third frequency clump to generate the second distribution scheme.
5. The system of claim 4 , wherein the third frequency bin and the fourth frequency bin are separated a second distance, the second distance different than the first distance.
6. The system of claim 5 , wherein the scrambler is to shift the watermark symbols of the first watermark layer and the second watermark layer distributed to a fifth frequency bin in the first frequency clump to a sixth frequency bin in a fourth frequency clump to generate the second distribution scheme, fifth frequency bin and the sixth frequency bin are separated a third distance, the third distance different than the first distance or the second distance.
7. The system of claim 6 , wherein the scrambler is to progressively shift the watermark symbols such that the first distance is less than the second distance, and the second distance is less than the third distance.
8. The system of claim 6 , wherein the scrambler is to randomly shift the watermark symbols.
9. The system of claim 3 , wherein with the shift of the watermark symbols from the first frequency clump to the second frequency clump, the scrambler is to shift the watermark symbols distributed in corresponding frequency bins in other frequency clumps by the first distance.
10. The system of claim 2 , wherein for n number of frequency bins in a frequency clump, the scrambler is to perform n−1 shifts of the watermark symbols of the first watermark layer and the second watermark layer to generate the second distribution scheme, different ones of the shifts moving the watermark symbols between different frequency clumps so the shifts are of different distances.
11. The system of claim 2 , wherein the scrambler is to further shift the watermark symbols of the first watermark layer and the second watermark layer distributed to a third frequency bin in the first frequency clump to a fourth frequency bin in the first frequency clump.
12. The system of claim 1 , wherein the sequence includes shifting the watermark symbols in the second watermark layer in the frequency clumps by a different distance for the different frequency clumps.
13. The system of claim 12 , wherein the sequence is a first sequence, the scrambler to:
map the watermark symbols to the plurality of frequency bins in the plurality of frequency clumps according to the first distribution scheme to create a third watermark layer having a third combination of the frequency bins, the third combination of the frequency bins at least partially overlapping with the first combination of the frequency bins and the second combination of the frequency bins;
determine a second sequence for shifting watermark symbols among the frequency bins; and
generate the second distribution scheme to map the watermark symbols in the third layer in the frequency clumps in accordance with the second sequence.
14. The system of claim 13 , wherein the second sequence includes shifting the watermark symbols in the third watermark layer in the frequency clumps by a different distance for the different frequency clumps.
15. The system of claim 14 , wherein the scrambler is to:
determine respective differences between the shifts of the second layer in the first sequence and the shifts of the third layer in the second sequence for the frequency clumps;
compare the differences;
determine if any two of the difference are equal; and
in response to two of the differences being equal, determine a third sequence for shifting the watermark symbols in the third watermark layer to replace the second sequence.
16. The system of claim 1 , wherein the scrambler is to randomly reorganize the watermark symbols in the second watermark layer based on the first watermark layer, and the sequence includes shifting the watermark symbols in the second watermark layer in the frequency clumps by a different distance for the different frequency clumps.
17. The system of claim 1 , wherein the sequence is a first sequence, and the frequency bins contain a pair of symbols that include a symbol from the first layer and a symbol from the second layer, the scrambler to:
determine if a pair of symbols shares more than one frequency bin;
based on a determination that a pair of symbols shares more than one frequency bin, determine a second sequence for shifting watermark symbols between frequency bins; and
map the watermark symbols in accordance with the second sequence to generate the second distribution scheme.
18. An encoder for encoding an audio signal with a watermark, the encoder comprising:
a parser to:
divide the audio signal into a plurality of frequency clumps with a plurality of adjacent frequency bins in the plurality of frequency clumps;
divide the watermark into N watermark symbols; and
distribute the watermark symbols to the plurality of frequency bins in the plurality of frequency clumps in accordance with a distribution scheme to create N watermark layers, so that combinations of N watermark symbols that include one watermark symbol from each watermark layer share a maximum of N−1 frequency bins; and
a synthesizer to synthesize an encoded audio signal with the watermark symbols distributed in the audio signal in accordance with the distribution scheme.