PHASELOCK - Phaselock Gabor coefficients

Usage

c=phaselock(c,a);

Description

phaselock(c,a) phaselocks the Gabor coefficients c. The coefficients must have been obtained from a dgt with parameter a.

Phaselocking the coefficients modifies them so as if they were obtained from a time-invariant Gabor system. A filter bank produces phase locked coefficients.

Phaselocking of Gabor coefficients correspond to the following transform: Consider a signal f of length L and define \(N=L/a\). The output from c=phaselock(dgt(f,g,a,M),a) is given by

\begin{equation*} c\left(m+1,n+1\right)=\sum_{l=0}^{L-1}f(l+1)e^{-2\pi im(l-na)/M}\overline{g(l-an+1)} \end{equation*}

where \(m=0,\ldots,M-1\) and \(n=0,\ldots,N-1\) and \(l-an\) is computed modulo L.

phaselock(c,a,'lt',lt) does the same for a non-separable lattice specified by lt. Please see the help of matrix2latticetype for a precise description of the parameter lt.

References:

M. Puckette. Phase-locked vocoder. Applications of Signal Processing to Audio and Acoustics, 1995., IEEE ASSP Workshop on, pages 222 --225, 1995.