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KOZ Scalable Audio

Speaker:陳繼大

An Introduction

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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 cross spectral method for improved frequency resolution.”, Proceedings of the IEEE-SP International Symposium on Time-Frequency and Time-Scale Analysis. IEEE Press, October 1998.

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References (cont.)

“KOZ scalable audio compression” SO/IEC JTC 1/SC 29/WG11 M12253

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Outline

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

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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

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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

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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

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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

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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.

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Double-scroll oscillator (cont.)

Double-scroll oscillator: One kind of chaotic system Nonlinear differential equations

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Double-scroll oscillator (cont.)

where

Parameters: C, L, G, m, B

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Double-scroll oscillator (cont.)

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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

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Double-scroll oscillator (cont.)

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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

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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 dtetwTtfwTF ti

)()(),(

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High Freq. Resolution Analysis (cont.)

Channelized CPS if f(t) is tone

2* |),(|),2/(),2/(

TFeTFTF i

))),2/(),2/(arg(1(lim

))),((arg(

00*

0

0

TFTF

TFT

)))),2/(),2/(arg(1(lim( 00

*

0

TFTFE

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High Freq. Resolution Analysis (cont.)

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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)

1,),(

bbaaab

babaU

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KOZ Scalable Audio

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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.

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KOZ Scalable Audio (cont.)

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KOZ Scalable Audio (cont.)

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Results

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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”