ThreeBandToneControl

Overview

Three band equalizer

Discussion

This module implements a three band tone control floating point module. Low shelf filter is used for low frequency band with normalised gain with respect to mid band gain. Similarly for high frequency band, high shelf filter is used with normalized gain with respect to mid gain. Finally scale smoothly the entire signal with mid band gain.

Type Definition

CODE

typedef struct _ModuleThreeBandToneControl
{
    ModuleInstanceDescriptor instance;            // Common Audio Weaver module instance structure
    FLOAT32 smoothingTime;                        // Time constant of the smoothing process.
    FLOAT32 lowFreq;                              // Low band center frequency, in Hz.
    FLOAT32 midFreq;                              // Mid band center frequency, in Hz.
    FLOAT32 highFreq;                             // High band center frequency, in Hz.
    FLOAT32 lowGain;                              // Low band gain, in dB.
    FLOAT32 midGain;                              // Mid band gain, in dB.
    FLOAT32 highGain;                             // High band gain, in dB.
    INT32 filterUpdateActive;                     // Boolean that is set when updating coefficients.
    FLOAT32 smoothingCoeff;                       // Smoothing coefficient for the filter coefficients.
    FLOAT32 midTargetGain;                        // Target gain of the mid frequency gain.
    FLOAT32 midCurrentGain;                       // Current gain of the mid frequency gain.
    FLOAT32 midSmoothingCoeff;                    // Sample-by-sample smoothing coefficient of the mid frequency gain.
    FLOAT32* lowerTargetCoeffs;                   // Target coefficients for the low frequency shelf.
    FLOAT32* lowerCurrentCoeffs;                  // Current coefficients for the low frequency shelf.
    FLOAT32* lowerState;                          // State variables for the low frequency shelf.
    FLOAT32* upperTargetCoeffs;                   // Target coefficients for the high frequency shelf.
    FLOAT32* upperCurrentCoeffs;                  // Current coefficients for the high frequency shelf.
    FLOAT32* upperState;                          // State variables for the high frequency shelf.
} ModuleThreeBandToneControlClass;

Variables

Properties

Name	Type	Usage	isHidden	Default value	Range	Units
smoothingTime	float	parameter	0	20	0:1000	msec
lowFreq	float	parameter	0	60	30:200	Hz
midFreq	float	parameter	0	600	200:4000	Hz
highFreq	float	parameter	0	6000	4000:20000	Hz
lowGain	float	parameter	0	0	-12:12	dB
midGain	float	parameter	0	0	-12:12	dB
highGain	float	parameter	0	0	-12:12	dB
filterUpdateActive	int	parameter	1	1	Unrestricted
smoothingCoeff	float	parameter	1	0.03278	Unrestricted
midTargetGain	float	parameter	1	1	Unrestricted
midCurrentGain	float	parameter	1	1	Unrestricted
midSmoothingCoeff	float	parameter	1	0.001041	Unrestricted
lowerTargetCoeffs	float*	parameter	1	[5 x 1]	Unrestricted
lowerCurrentCoeffs	float*	parameter	1	[5 x 1]	Unrestricted
lowerState	float*	state	1	[2 x 1]	Unrestricted
upperTargetCoeffs	float*	parameter	1	[5 x 1]	Unrestricted
upperCurrentCoeffs	float*	parameter	1	[5 x 1]	Unrestricted
upperState	float*	state	1	[2 x 1]	Unrestricted

Pins

Input Pins

Name: in

Description: audio input

Data type: float

Channel range: Unrestricted

Block size range: Unrestricted

Sample rate range: Unrestricted

Complex support: Real

Output Pins

Name: out

Description: audio output

Data type: float

MATLAB Usage

File Name: three_band_tone_control_module.m

CODE

 M=three_band_tone_control_module(NAME)
 Implements a three band tone control module.  Arguments:
    NAME - name of the module.