Constant Q Transform
Matlab code to calculate a constant Q transform by the "brute force method" as described in:
Brown, J.C., (1991). ``Calculation of a Constant Q Spectral Transform" J. Acoust. Soc. Am. 89, 425-434.
logftS.m calculates a transformation matrix using genlgkern.m and logft.m with input minimum and maximum frequencies and geometric spacing of the bins.
The transform can also be done as a single matrix multiplication with kerncos and kernsin from above and infile shaped by makmatrix.m.
T = kerncos + i * kernsin;
cqtrans = T * makmatrix( infile, windsiz, hopsiz);
A really inadequate inverse can be approximated using:
ilogft2.m (this is only useful for looking at a single input frame)
I'd love to hear about a decent inverse.