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DIGITAL WATERMARKING OF AUDIO SIGNALS USING A PSYCHOACOUSTIC AUDITORY MODEL AND SPREAD SPECTRUM THEORY *

DIGITAL WATERMARKING OF AUDIO SIGNALS USING A PSYCHOACOUSTIC AUDITORY MODEL AND SPREAD SPECTRUM THEORY *. By: Ricardo A. Garcia. MIT Media Lab Machine Listening Group. *Research done at: University of Miami School of Music 1999. Objectives:.

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DIGITAL WATERMARKING OF AUDIO SIGNALS USING A PSYCHOACOUSTIC AUDITORY MODEL AND SPREAD SPECTRUM THEORY *

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  1. DIGITAL WATERMARKING OF AUDIO SIGNALS USING A PSYCHOACOUSTIC AUDITORY MODEL AND SPREAD SPECTRUM THEORY* By: Ricardo A. Garcia MIT Media Lab Machine Listening Group *Research done at: University of Miami School of Music 1999

  2. Objectives: • Design an algorithm and implement a system capable of embedding digital watermarks into audio signals • Use spread spectrum techniques to generate the watermark. • Use a psychoacoustic auditory model to shape the watermark

  3. Watermark characteristics: • Not perceptible (transparent) • Resistant to degradation • Removal attempts • Transmission by analog/digital channel • Sub-band coders • Original audio is not required in recovery

  4. Conference Overview: 1. a) Psychoacoustic Auditory Model b) Noise shaping (watermark embedding) c) Spread Spectrum watermark generation 2. Developed system 3. Examples and System Performance 4. Conclusions

  5. a) PSYCHOACOUSTIC AUDITORY MODEL • Simultaneous frequency masking • Calculate an approximated masking threshold T(z)- frequency holes -

  6. Psychoacoustic Auditory Model

  7. Masking Threshold T(z)

  8. b) NOISE SHAPING • Replace components below masking threshold with components from a broadband noise-like signal (watermark) • Level of the watermark below threshold • Each critical band has its own scaling factor

  9. Noise Shaping

  10. c) SPREAD SPECTRUM • Communication system • Uses all the available spectrum (broadband, noise-like) • Each channel use an orthogonal code • All other channels appear as “noise”

  11. FDMA TDMA CDMA spread spectrum

  12. Information = data sequence (watermark) • Jammer = music signal (after auditory model)

  13. Direct Sequence Spreading Uncoded Direct Sequence Binary Phase Shift Keying Uncoded DS/BPSK • Data sequence (watermark) • Modulator (fo) • PN sequence

  14. Uncoded DS/BPSK

  15. De-Spreading and Data Recovery

  16. Coded DS/BPSK • Transmitter: • Repeat Code (m) • Interleaving • Receiver: • De-interleaving • Decoder (decision rule)

  17. 2. PROPOSED SYSTEM Transmission: watermark generation and embedding

  18. Reception: watermark recovery

  19. 3. EXAMPLES Original Audio One watermark After Auditory Model Shaped watermark Residual Watermarked Audio

  20. SYSTEM PERFORMANCE • Survival over different channels • MPEG, Mini Disc, Two consecutive D/A - A/D, Analog Tape, FM Stereo Radio, FM Mono Radio, FM Mono Radio (weak signal), AM Radio • (next slide) • Listening test • ABX test, 40 trials • (-2 db, 24 correct id.), (-4 db, 19), (-6 db, 19)

  21. MPEG LAYER 3 Level: -2 dB

  22. 4. CONCLUSIONS • The perceptual quality of the audio signal was retained • The watermark signal survives to different removal attacks (redundancy) • Few parameters are needed at the receiver to recover the watermark

  23. FURTHER RESEARCH • Performance with different types of music • Changes in the playback speed of the signal • Bit error detection and recovery • Optimal spread spectrum parameters • Multiple watermark embedding • Crosstalk interference

  24. Contact Information • Ricardo A. Garcia • Email: rago@media.mit.edu • Website: http://www.media.mit.edu/~rago

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