Subband processing with lapped transforms and modulated FBs

[Juuso Alhava]

Dear good people,

Below is a download link for my MFB/LT function collection. 
(The efforts to make this package fully compatible with the 
OCTAVE is still in progress. My apolgies beforehand for the 
error messages in prototype filter design)

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In a nutshell: modulated filter banks[lapped transforms] are discrete
time-frequency
analysis tools where the sinusoidal waveforms are localized with a prototype 
filter[window function]. Based on the sheer count of published papers, one
would 
also expect to find some pieces of useful code from the web. If such
collections exist,
they seem to be hidden from the search engines.

But in case your research/study interests coincide with critically sampled
perfect 
reconstruction systems, the following link might be useful:

http://www.students.tut.fi/~jalhava/lt/intro.html

You can download there a collection of MFB algorithms and some design
routines.
The www-pages also serve as a tutorial for the LT-toolbox. The m-file
package 
is still under developement so I have not verified the functionality with 
other MATLAB versions than r2007a (windows).

A major rewrite is under consideration but there still some unsolved
problems:

* Is it possible to factorize any 2-channel PR system into lifting steps?
  Namely, I can generate such low-delay biorthogonal low/highpass system
  where MATLAB filt2ls-function fails. Is this a wavelet toolbox "feature"
  or what?

* Non-linear optimization problem solver for OCTAVE that is comparable with
  the MATLAB's fmincon.

* 2-D filter banks: What is the fastest "direction" to apply the filtering?
  Block-wise, column-wise, does it make sense to divide the actual filtering
  into modulation and polyphase parts?

* Handling the signal edges without allocating new space for the extended
data 
  matrix

But anyway, any contribution for this non-profit project is welcome. 
Improvements, faster code and new features? Please, share your code.

Best subband processing wishes,
Juuso Alhava
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