Post-compression hidden data transport
First Claim
1. A method for providing auxiliary data subband samples in a compressed subband coded digital audio data stream, comprising the steps of:
- providing a plurality of audio subband samples from said data stream;
providing a data carrier sequence;
modulating said data carrier sequence by an auxiliary data signal to provide said auxiliary data subband samples;
combining said auxiliary data subband samples with corresponding audio subband samples to produce combined subband samples in which said auxiliary data subband samples are carried substantially inaudibly; and
providing said combined subband samples for transport in said digital audio data stream.
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0 Petitions
Accused Products
Abstract
Auxiliary data subband samples representing an auxiliary data signal are transported in a subband-coded compressed digital audio signal without decompressing the data. A pre-existing packetized data stream is provided to an input of a encoder. Subband audio samples are extracted from the packet stream and normalized if required. The data to be transported modulates data carrier subbands including, for example, a pseudo-noise (PN) spread spectrum signal, each subband of which has a bandwidth corresponding to those of the digital audio signal. The data carrier sequence can also include a sparse PN sequence, sample twiddle sequence, or a bit twiddle sequence. The modulated data carrier sequence is combined with the audio subband samples to form a combined signal in which the auxiliary data subband samples are carried. The combined signal is then multiplexed into the pre-existing packet stream. In a decoder, the combined signal is demodulated to recover the auxiliary data signal. The recovered auxiliary data signal is carried substantially inaudibly in the audio signal and is spectrally shaped according to the audio signal to enhance concealment.
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Citations
43 Claims
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1. A method for providing auxiliary data subband samples in a compressed subband coded digital audio data stream, comprising the steps of:
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providing a plurality of audio subband samples from said data stream; providing a data carrier sequence; modulating said data carrier sequence by an auxiliary data signal to provide said auxiliary data subband samples; combining said auxiliary data subband samples with corresponding audio subband samples to produce combined subband samples in which said auxiliary data subband samples are carried substantially inaudibly; and providing said combined subband samples for transport in said digital audio data stream. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for recovering auxiliary data subband samples representative of an auxiliary data signal from a compressed digital data stream, said auxiliary data subband samples being provided by modulating a first data carrier sequence by said auxiliary data signal, said auxiliary data subband samples being carried with audio subband samples in combined subband samples in said compressed digital data stream, comprising the steps of:
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recovering said combined subband samples from said data stream; providing a recovery data carrier sequence corresponding to said first data carrier sequence; and demodulating said combined subband samples using said recovery data carrier sequence to recover said auxiliary data subband samples from said recovered combined subband samples. - View Dependent Claims (12, 13, 14, 15, 16, 17)
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18. An encoder for providing auxiliary data subband samples, which are representative of an auxiliary data signal, in a compressed subband coded digital audio data stream, comprising:
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an input terminal for receiving said digital audio data stream and providing a plurality of audio subband samples; a data carrier generator for providing a data carrier sequence; a modulator for modulating said data carrier sequence by said auxiliary data signal to provide said auxiliary data subband samples; a combiner coupled to said modulator for combining said auxiliary data subband samples with corresponding audio subband samples to produce combined subband samples in which said auxiliary data subband samples are carried substantially inaudibly; and an output terminal coupled to said combiner for providing said combined subband samples for transport in said digital audio data stream. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27)
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28. A decoder for recovering auxiliary data subband samples which are representative of an auxiliary data signal from a compressed digital data stream, said auxiliary data subband samples being provided by modulating a first data carrier sequence by said auxiliary data signal, said auxiliary data subband samples being carried with audio subband samples in combined subband samples in said compressed digital data stream, comprising:
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means for recovering said combined subband samples from said compressed digital data stream; means for providing a recovery data carrier sequence corresponding to said first data carrier sequence; and a demodulator for demodulating said combined subband samples using said recovery data carrier sequence to recover said auxiliary data subband samples from said recovered combined subband samples. - View Dependent Claims (29, 30, 31, 32, 33, 34, 35, 36, 37)
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38. A compressed digital data storage media, comprising:
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(i) storage means for storing combined subband samples including audio subband samples which represent an audio signal, and auxiliary data subband samples which represent an auxiliary data signal; said auxiliary data subband samples being provided by modulating a data carrier sequence by said auxiliary data signal over at least one subband corresponding to said audio subband samples; said auxiliary data signal being carried substantially inaudibly in said audio signal; said auxiliary data signal being spectrally shaped according to said audio signal; and (ii) means for allowing the recovery of said auxiliary data signal from said auxiliary data subband samples. - View Dependent Claims (39, 40, 41, 42, 43)
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Specification