Overview

M-input x N-output mixer

Discussion

This module implements a full M-input x N-output mixer with a total of MxN coefficients. N = number of channels on the one output pin. M = sum of number of channels on all input pins. When using the module in MATLAB, the coefficients are contained in the .coeffs matrix with the gain from the ith input to the jth output found at coeffs(i, j). From the C code point of view, the .coeffs array is a one dimensional array of length MxN. The gain from input m (0 <= m <= M-1) to output n (0 <= n <= N-1) is stored at:

coeffs[m + n*M]

Put another way, the first M coefficients are the gains needed to compute the first output channel. The next M coefficients are the gains needed to compute the second output channel, and so out.

The mixer implements smoothing on a block-by-block basis. Standard 1st order exponential smoothing is used. Gain adjustments are made to the coeffs matrix. Internally, the module holds a second matrix of instantaneous gains, currentCoeff, which smoothly approaches coeffs. The rate of the smoothing operation is controlled by smoothingTime.

When the module is bypassed, it copies the ith input channel to the ith output channel. If the module has more output channels than input channels, the remaining output channels are set to 0.

Type Definition

typedef struct _ModuleMixerV3Fract32
{
    ModuleInstanceDescriptor instance;            // Common Audio Weaver module instance structure
    INT32 maxNonZero;                             // Maximum number of non zero coefficients.
    INT32 postShift;                              // Number of bits to shift
    FLOAT32 gainScale;                            // Scale coefficients based on postShift.
    INT32 numIn;                                  // Number of input channels.
    FLOAT32* gain;                                // Linear gain.
    fract32* nonZeroGainFract32;                  // Instanteous fract32 gain being applied.
    SparseItem * table;                           // Internal data holding data for quick processing
} ModuleMixerV3Fract32Class;

Variables

Properties

Name	Type	Usage	isHidden	Default value	Range	Units
maxNonZero	int	const	1	2	Unrestricted
postShift	int	const	1	4	Unrestricted
gainScale	float	derived	1	0.0625	Unrestricted
numIn	int	derived	1	1	Unrestricted
gain	float*	parameter	0	[1 x 2]	-60:20
nonZeroGainFract32	fract32*	state	1	[2 x 1]	Unrestricted
table	SparseItem *	parameter	1		Unrestricted

Pins

Input Pins

Name: in1

Description: Input signal

Data type: fract32

Channel range: Unrestricted

Block size range: Unrestricted

Sample rate range: Unrestricted

Complex support: Real

Output Pins

Name: out

Description: audio output

Data type: fract32

MATLAB Usage

File Name: mixer_v3_fract32_module.m

 M=mixer_v3_fract32_module(NAME, NUMOUT, NUMINPIN, MAXNONZERO)
 Creates a mixer module for use in the Audio Weaver environment. 
 The mixer has multiple input pins and one output pin. Each of the pins 
 can contain multiple interleaved channels. The number of input channels 
 per input pin is determined by the upstream audio module. You must 
 specify the number of input pins and output channels.  
 
 Arguments:
   NAME - name of the module.
   NUMOUT - number of output channels.
   NUMINPIN - number of input pins.
   MAXNONZERO - maximum number of non zero coefficients.