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KOZ Scalable Audio

KOZ Scalable Audio. An Introduction. Speaker: 陳繼大. References. K. M. Short et al, "An Introduction to the KOZ Scalable Audio Compression Technology", AES 118th Convention Paper, Barcelona, May 2005, Preprint 6446

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KOZ Scalable Audio

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  1. KOZ Scalable Audio An Introduction Speaker:陳繼大

  2. References • K. M. Short et al, "An Introduction to the KOZ Scalable Audio Compression Technology", AES 118th Convention Paper, Barcelona, May 2005, Preprint 6446 • M. K. Johnson, "Controlled Chaos and Other Sound Synthesis Techniques," Thesis for the Degree of Bachelor of Science, University of New Hampshire, May 2000 • Douglas J. Nelson, and Kevin M. Short, “A channelized crossspectral method for improved frequency resolution.”, Proceedings of the IEEE-SP International Symposium on Time-Frequency and Time-Scale Analysis. IEEE Press, October 1998. P2

  3. References (cont.) • “KOZ scalable audio compression” SO/IEC JTC 1/SC 29/WG11 M12253 P3

  4. Outline • Introduction • Double-scroll oscillator • High Freq. Resolution Analysis • Unified Domain • KOZ Scalable Audio • Results • Conclusions P4

  5. Introduction • Traditional transform/subband based codecs encode data by quantizing the coefficients according to psychoacoustic model • Parametric coding is another way for coding – it records the parameters of models, rather than coefficients. • KOZ scalable audio belongs to parametric coding methods • KOZ scalable audio takes Chaos system as the model • The Chaotic system is a nonlinear system P5

  6. Introduction (cont.) • Features of the KOZ codec • Flexibility over a wide range of bitrates • Both small-step and large-step scalability • High resolution objects allows easy decoder-side post-processing • Integrated Digital Rights Management P6

  7. Double-scroll oscillator • Chaotic system: • nonlinear dynamical systems • deterministic mathematical object • sensitive dependence on initial conditions • predictable over a short period of time • unpredictable in terms of long-term behavior P7

  8. Double-scroll oscillator (cont.) • Cupolets: • Output periodic waveforms of Chaotic system • control process requires only on the order of 16 bits of information • but the cupolets can be as simple as a sine wave or so complex that they have more than 200 harmonics in their spectrum P8

  9. Double-scroll oscillator (cont.) • A chaotic system will settle down onto a complicated structure called an attractor – settle down onto the same attractor no matter what initial conditions are used • A chaotic system in its natural state is aperiodic. • To stabilize these orbits – simply perturbing the state of the system in certain fixed locations by a tiny amount. P9

  10. Double-scroll oscillator (cont.) • Double-scroll oscillator: • One kind of chaotic system • Nonlinear differential equations P10

  11. Double-scroll oscillator (cont.) • where • Parameters: • C, L, G, m, B P11

  12. Double-scroll oscillator (cont.) P12

  13. Double-scroll oscillator (cont.) • Double-scroll attractor can be controlled in such a way that the trajectories around it become periodic. • Control perturbing: • a bit string, generally of 16 bits • applied at an intersection with the control line • periodic orbits are in one-to-one correspondence with the control string used, independent of the initial state of the system P13

  14. Double-scroll oscillator (cont.) P14

  15. High Freq. Resolution Analysis • Detect (the accurate freq.) of tones • IF-based methods • Differentiation of the signal phase • fail completely if the signal environment consists of more than one sinusoid • CPS (Cross Power Spectral) • Time-averaged IF method • Phase differentiation is applied to a time-varying Fourier transform • Fourier transform is used to “channelize” the signal isolating the tones P15

  16. High Freq. Resolution Analysis (cont.) • Improved (channelized) CPS estimator • CPS can not detect and estimate tones which are not well separated • Employ a second Fourier transform • TVFT: • Time varying Fourier transform P16

  17. High Freq. Resolution Analysis (cont.) • Channelized CPS • if f(t) is tone P17

  18. High Freq. Resolution Analysis (cont.) P18

  19. Unified Domain • Convert the multiple channels into Special unitary group • Special unitary group • group of n×n unitary matrices • subgroup of the unitary group • SU(2) P19

  20. KOZ Scalable Audio P20

  21. KOZ Scalable Audio (cont.) • Prioritize the components • Psychoacoustics are used • in order of perceptual importance • Classes of objects are then sorted in order of their “perceptual relevance” • Objects are segregated and written to the floating-point .CCA file format. • Scalability of KOZ is fulfilled by sorting. P21

  22. KOZ Scalable Audio (cont.) P22

  23. KOZ Scalable Audio (cont.) P23

  24. Results P24

  25. Conclusions • KOZ scalable audio takes chaotic system to model audio signal • CPS is applied to find tones and their accurate freq. • Scalability is fulfilled by sorting classes of objects with order of their “perceptual relevance” P25

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