Aki Härmä,
Researcher, (frequency masking & noise shaping, complex valued WLP for
stereo, complex valued lattice structures, etc.)
Markus Vaalgamaa, Research
Assistant, (temporal noise shaping TNS) [starts spring-98]
SHORT INFO
The project started in summer 1995 and was at the begining financiated
by The Foundation for
Finnish Inventions. Later the main supporter has been The
Academy of Finland. New extension in the project starts in spring-98.
This part is financiated by Tekes
(Technology Development Centre) and two Finnish companies.
MAIN R&D DIRECTIONS
The general goal is to study and test perceptually motivated time-frequency
methods and techniques for audio coding. Our main interest is to develop
and apply frequency warping technigues. FAM and FAMlet
classes have provided promising tools and theoretical background for these
new developments.
Topics of Basic Research
FAM operator and related differential equations
FAM class and differential equation of nonuniform transmission-line
Human auditory time-frequency perception
Auditory filterbank generation by using FAMlet transform
Time-frequency properties of created auditory filterbanks
Fast algorithms for ERB-rate FAMlet transform and auditory filterbank
computation
On the basic research level a central problem has been computationally
effective algorithms for FAMlet transform able to produce good approximations
for any type of frequency warping. Also effective algorithms are needed
for auditory filterbank and spectrogram computation and warped autocorrelation
computation for warped linear prediction (WLP). During fall-96 and
spring-97 a novel block recursive warping method was developed. A novel
idea of block recursive FAMlet transform combined with Fourier transform
to form a block recursive auditory filterbank is published in EUROSPEECH'97.
(more about basic research)
