Methods and apparatus for embedding codes in compressed audio data streams
Methods and apparatus for embedding codes in compressed audio data streams are disclosed. An example apparatus disclosed herein to embed a code in a compressed audio data stream comprises an unpacking unit to determine a plurality of transform coefficients associated with the compressed audio data stream, the plurality of transform coefficients being represented by a respective plurality of mantissas and a respective plurality of scale factors, and an embedding unit to modify a mantissa in the plurality of mantissas and a corresponding scale factor in the plurality of scale factors to embed the code in the compressed audio data stream.
1. A method to embed a watermark in a compressed data stream, the method comprising:
obtaining a set of transform coefficients from the compressed data stream, the set of transform coefficients comprising a set of mantissas and a set of scale factors; and
modifying, with a processor, a first one of the mantissas and a first one of the scale factors corresponding to a first transform coefficient from the set of transform coefficients based on a second mantissa and a second scale factor associated with a temporary watermarked transform coefficient to embed the watermark in the compressed data stream without uncompressing the compressed data stream.
2. A method as defined in claim 1 wherein modifying the first one of the mantissas and the first one of the scale factors comprises:
reducing the first one of the scale factors by a unit of resolution to determine the second scale factor; and
quantizing the temporary watermarked transform coefficient based on the second scale factor to determine the second mantissa.
3. A method as defined in claim 1 wherein the set of scale factors comprises a set of exponents and a set of fractional multipliers, and further comprising modifying at least one of a first one of the exponents or a first one of the fractional multipliers corresponding to the first one of the scale factors to modify the first one of the scale factors.
4. A method as defined in claim 3 wherein modifying the first one of the scale factors comprises modifying the first one of the exponents and the first one of the fractional multipliers.
5. A method as defined in claim 1 wherein modifying the first one of the mantissas and the first one of the scale factors comprises:
determining the second scale factor to be the first one of the scale factors reduced by a unit of resolution;
quantizing the temporary transform coefficient based on the second scale factor;
encoding the quantized temporary transform coefficient based on a same codebook used to encode the first one of the mantissas to determine the second mantissa; and
replacing the first one of the mantissas and the first one of the scale factors with the second mantissa and the second scale factor.
6. A method as defined in claim 1 wherein the compressed data stream comprises a compressed audio data stream and the set of transform coefficients comprises a set of modified discrete cosine transform coefficient.
7. A method as defined in claim 1 wherein the watermark corresponds to a frequency change in audio content carried by the compressed data stream, and the watermark is recoverable from a presentation of the audio content without access to the compressed data stream.
8. A machine readable storage disk or a machine readable storage device comprising circuitry, the machine readable storage disk or storage device comprising machine readable instructions which, when executed, cause a machine to at least:
obtain a set of transform coefficients from a compressed data stream, the set of transform coefficients comprising a set of mantissas and a set of scale factors; and
modify a first one of the mantissas and a first one of the scale factors corresponding to a first transform coefficient from the set of transform coefficients based on a second mantissa and a second scale factor associated with a temporary watermarked transform coefficient to embed a watermark in the compressed data stream without uncompressing the compressed data stream.
9. A machine readable storage disk or storage device as defined in claim 8 wherein to modify the first one of the mantissas and the first one of the scale factors, the machine readable instructions, when executed, further cause the machine to:
reduce the first one of the scale factors by a unit of resolution to determine the second scale factor; and
quantize the temporary watermarked transform coefficient based on the second scale factor to determine the second mantissa.
10. A machine readable storage disk or storage device as defined in claim 8 wherein the set of scale factors comprises a set of exponents and a set of fractional multipliers, and the machine readable instructions, when executed, further cause the machine to modify at least one of a first one of the exponents or a first one of the fractional multipliers corresponding to the first one of the scale factors to modify the first one of the scale factors.
11. A machine readable storage disk or storage device as defined in claim 10 wherein to modify the first one of the scale factors, the machine readable instructions, when executed, further cause the machine to modify the first one of the exponents and the first one of the fractional multipliers.
12. A machine readable storage disk or storage device as defined in claim 8 wherein to modify the first one of the mantissas and the first one of the scale factors, the machine readable instructions, when executed, further cause the machine to:
determine the second scale factor to be the first one of the scale factors reduced by a unit of resolution;
quantize the temporary transform coefficient based on the second scale factor;
encode the quantized temporary transform coefficient based on a same codebook used to encode the first one of the mantissas to determine the second mantissa; and
replace the first one of the mantissas and the first one of the scale factors with the second mantissa and the second scale factor.
13. A machine readable storage disk or storage device as defined in claim 8 wherein the compressed data stream comprises a compressed audio data stream and the set of transform coefficients comprises a set of modified discrete cosine transform coefficient.
14. A machine readable storage disk or storage device as defined in claim 8 wherein the watermark corresponds to a frequency change in audio content carried by the compressed data stream, and the watermark is recoverable from a presentation of the audio content without access to the compressed data stream.
15. An apparatus to embed a watermark in a compressed data stream, the apparatus comprising:
an unpacking unit to obtain a set of transform coefficients from the compressed data stream, the set of transform coefficients comprising a set of mantissas and a set of scale factors; and
an embedding unit to modify a first one of the mantissas and a first one of the scale factors corresponding to a first transform coefficient from the set of transform coefficients based on a second mantissa and a second scale factor associated with a temporary watermarked transform coefficient to embed a watermark in the compressed data stream without uncompressing the compressed data stream, at least one of the unpacking unit or the embedding unit comprising hardware.
16. An apparatus as defined in claim 15 wherein to modify the first one of the mantissas and the first one of the scale factors, the embedding unit is to:
reduce the first one of the scale factors by a unit of resolution to determine the second scale factor; and
quantize the temporary watermarked transform coefficient based on the second scale factor to determine the second mantissa.
17. An apparatus as defined in claim 15 wherein the set of scale factors comprises a set of exponents and a set of fractional multipliers, and the embedding unit is to modify at least one of a first one of the exponents or a first one of the fractional multipliers corresponding to the first one of the scale factors to modify the first one of the scale factors.
18. An apparatus as defined in claim 17 wherein to modify the first one of the scale factors, the embedding unit is to modify the first one of the exponents and the first one of the fractional multipliers.
19. An apparatus as defined in claim 15 wherein to modify the first one of the mantissas and the first one of the scale factors, the embedding unit is to:
determine the second scale factor to be the first one of the scale factors reduced by a unit of resolution;
quantize the temporary transform coefficient based on the second scale factor;
encode the quantized temporary transform coefficient based on a same codebook used to encode the first one of the mantissas to determine the second mantissa; and
replace the first one of the mantissas and the first one of the scale factors with the second mantissa and the second scale factor.
20. An apparatus as defined in claim 15 wherein the compressed data stream comprises a compressed audio data stream, the set of transform coefficients comprises a set of modified discrete cosine transform coefficient, the watermark corresponds to a frequency change in audio content carried by the compressed audio data stream, and the watermark is recoverable from a presentation of the audio content without access to the compressed data stream.