SbAECReset

Overview

Frequency domain subband adaptive filter

Discussion

Subband based mono echo canceler. This module works in conjunction with the WOLA filterbank modules. The module has two input pins. The first input is a single channel microphone signal and the second is a mono reference signal.

At instantiation time you specify the length of each subband filter. Then at run time, you specify the number of taps currently used. This allows you to easily vary the filter length at run time and verify performance and CPU load.

The module has optional residual noise suppression which is enabled via the enableRNS variable. By default, residual noise suppression is on and the output of the echo canceler (the error signal) is further reduced in level. The residual noise suppression is configured by a 7 element interpolation table. This table operates just like the Table X-Y module with configurable (X, Y) lookup points. The lookup table specifies values in dB for the input and output function

Module Pack

awe-mod-dspc-vui

ClassID

classID = 15008

Type Definition

typedef struct _ModuleSbAECReset
{
ModuleInstanceDescriptor instance;            // Common Audio Weaver module instance structure
INT32 maxTaps;                                // Maximum length of the filter
INT32 numTaps;                                // Current length of the filter
FLOAT32 V;                                    // Adaptation constant
FLOAT32 smoothingTime;                        // Time constant of the smoothing process.
FLOAT32 A;                                    // Smoothing factor
FLOAT32 p0;                                   // Starting value for covariance estimate
INT32 numIter;                                // Number of iterations of adaptive loop
INT32 enableRNS;                              // Enable residual noise suppression
FLOAT32 bypassTime;                           // Time in millisecond that it takes the system to reconverge after it is bypassed
INT32 bypassBlocks;                           // Number of processing blocks that we count up as we time the bypass operation
INT32 bypassCount;                            // Internal counter while AEC is bypassed
INT32 bypassOn;                               // Indicates when the module is in bypass mode
FLOAT32 PResetValue;                          // P matrix is set to this value after reset
INT32 stateIndex;                             // Circular buffer index.  [0 numTaps-1]
INT32 RNS_numPoints;                          // Number of values in the lookup table. The total table size is [maxPoints 2].
INT32 RNS_order;                              // Order of the interpolation. This can be either 2 (for linear) or 4 (for pchip).
FLOAT32* WW1;                                 // Adaptive filter coefficients.
FLOAT32* P;                                   // Real estimation error covariance matrix.
FLOAT32* CC;                                  // Complex state variables (previous inputs).
FLOAT32* Pplus;                               // Intermediate result (real scratch).
FLOAT32* Wplus;                               // Intermediate result (complex scratch).
FLOAT32* energyC;                             // Intermediate result (real scratch).
FLOAT32* mu;                                  // Intermediate result (real scratch).
FLOAT32* W2;                                  // Residual noise suppression weights.
FLOAT32* RNS_table;                           // Lookup table. The first row is the X values and the second row is the Y values.
FLOAT32* RNS_polyCoeffs;                      // Interpolation coefficients returned by the grid control.
} ModuleSbAECResetClass;

Variables

Properties

Name	Type	Usage	isHidden	Default Value	Range	Units
maxTaps	int	const	0	16	Unrestricted	samples
numTaps	int	parameter	0	16	1:1:16	samples
V	float	const	0	0.5	Unrestricted
smoothingTime	float	parameter	0	10	0.1:1000	sec
A	float	derived	0	1	0:1
p0	float	parameter	0	1	Unrestricted
numIter	int	parameter	0	1	1:20
enableRNS	int	parameter	0	1	0:1:1
bypassTime	float	parameter	0	2000	Unrestricted
bypassBlocks	int	derived	0	96000	Unrestricted
bypassCount	int	state	0	0	Unrestricted
bypassOn	int	state	0	0	Unrestricted
PResetValue	float	parameter	0	0.001	Unrestricted
stateIndex	int	state	1	0	Unrestricted
RNS_numPoints	int	const	1	7	4:1:1000
RNS_order	int	const	1	2	2:2:4
WW1	float*	state	0	[16 x 32]	Unrestricted
P	float*	state	0	[16 x 32]	Unrestricted
CC	float*	state	0	[16 x 32]	Unrestricted
Pplus	float*	state	0	[1 x 16]	Unrestricted
Wplus	float*	state	0	[1 x 16]	Unrestricted
energyC	float*	state	0	[16 x 32]	Unrestricted
mu	float*	state	0	[1 x 16]	Unrestricted
W2	float*	state	0	[32 x 1]	Unrestricted
RNS_table	float*	parameter	1	[2 x 7]	Unrestricted
RNS_polyCoeffs	float*	state	1	[4 x 6]	Unrestricted

Pins

Input Pins


Name	reset
Description	Resets internal state
Data type	int
Channel range	1
Block size range	1
Sample rate range	Unrestricted
Complex support	Real


Name	dataIn
Description	Micro input
Data type	float
Channel range	1
Block size range	Unrestricted
Sample rate range	Unrestricted
Complex support	Complex


Name	reference
Description	Reference input
Data type	float
Channel range	1
Block size range	Unrestricted
Sample rate range	Unrestricted
Complex support	Complex

Output Pins


Name	errorSignal
Description	Error signal = difference between filter output and dataIn
Data Type	float

Matlab Usage

File Name: sb_aec_reset_module.m 
 M = sb_aec_reset_module(NAME, MAXTAPS) 
 Frequency domain subband echo canceler using a Kalman filter based 
 algorithm.  This version includes a reset pin allowing the internal 
 module state variables to be reset in case they lock up.  Arguments: 
    NAME - name of the module. 
    MAXTAPS - maximum length of each frequency domain complex adaptive filter