HARK version 1.1.0 Document : CMInverseMatrix

6.2.8 CMInverseMatrix

Module Overview

Calculates the inverse of the sound source correlation matrix.

Requested Files

None.

Usage

In what case is the node used?

The calculation node of the correlation matrix is the one created for the sound source from CMMakerFromFFT , CMMakerFromFFTwithFlag , and has the function to calculate the inverse matrix of the correlation matrix.

Typical Examples

Figure. 6.17 shows a usage example of CMInverseMatrix node.

INPUTCM input terminal is connected to a correlation matrix calculated from CMMakerFromFFT or CMMakerFromFFTwithFlag , etc. (type is Matrix<complex<float> > type, but to handle a correlation matrix, convert the three dimensional complex array to a two dimensional complex array and then output). OPERATION_FLAG is int type or bool type input, and specifies when to calculate the inverse matrix of the correlation matrix.

$\includegraphics[width=100mm]{fig/modules/CMInverseMatrix.eps}$

Figure 6.17: Network Example using CMInverseMatrix

I/O and property setting of the node

Table 6.21: Parameter list of CMInverseMatrix

Parameter	Type	Default	Unit	Description
NB_CHANNELS	`int`	8		Number of input channels $M$ of input signal
LENGTH	`int`	512		Frame length $NFFT$
FIRST_FRAME_EXECUTION	`bool`	false		Selection of the first frame execution
ENABLE_DEBUG	`bool`	false		ON/OFF of debugging information output

Input

INPUTCM: Matrix<complex<float> > type. A correlation matrix of each frequency bin. The $M$ -th order complex square array correlation matrix outputs $NFFT/2 + 1$ items. Matrix<complex<float> > contains rows corresponding to frequencies ( $NFFT/2 + 1$ rows), and columns containing the complex correlation matrix ( $M * M$ columns across).
OPERATION_FLAG: int type or bool type. Only when this input terminal is 1 or when true, the calculation of correlation matrix is performed.

Output

OUTPUTCM: Matrix<complex<float> > type. The correlation matrix after the inverse matrix calculation is output.

Parameter

NB_CHANNELS: int type. Number of channels for input signal. Equivalent to the order of the correlation matrix. Must match with the former correlation matrix used. Default value is 8.
LENGTH: int type. Default value is 512. FFT points at the time of Fourier transform. Must be matched till the former FFT length values.
FIRST_FRAME_EXECUTION: bool type. Default value is false. When true, OPERATION FLAG is always 0. Even when it is false, the operation is performed only on the first frame.
ENABLE_DEBUG: bool type. Default value is false. When true, output the frame number calculated to the standard output, during correlation matrix calculation.

Module Description

Calculates the inverse matrix of the correlation matrix. The correlation matrix is a complex three-dimensional array of size $k \times M \times M$ and the inverse matrix calculation $k$ times is performed as follows. Here, $k$ is the number of frequency bins ( $k = NFFT/2 + 1$ ), and $M$ is the number of channels in the input signal.

=- OUTPUTCM = zero_matrix(k,M,M) calculate{ IF OPERATION_FLAG FOR i = 1 to k OUTPUTCM[i] = inverse( INPUTCM[i] ) ENDFOR ENDIF }

The matrix that is output from OUTPUTCM terminal is initialized as a zero matrix, and maintains the final operational result from this point onward.