6.2.8 CMInverseMatrix

6.2.8.1 Module Overview

Calculates the inverse of the sound source correlation matrix.

6.2.8.2 Requested Files

None.

6.2.8.3 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. 6.18 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.

Figure 6.18: Network Example using CMInverseMatrix 

6.2.8.4 I/O and property setting of the node

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

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.

6.2.8.5 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.