(8.D.2.2 ) BalanceFract32
- Catherine Spain
Overview
Smooth Stereo Balance Module
Discussion
The Fractional Balance module smoothly scales left and right channels as specified by the balance parameter. The module has two multichannel input pins and two multichannel output pins. All dimensions of input and output pins are identical. The balance setting is automatically converted to target gains for left and right channels: gainL and gainR. gainL,R are computed from balance using the sine/cosine panning law: gainL = cos((1+balance)*pi/4), and gainR = sin((1+balance)*pi/4). Thus: full pan left-->gainL=1,gainR=0; full pan right-->gainL=0, gainR=1; balance=0, (centered) -->gainL=gainR=.707 . Internally currentGainL, currentGainR represent the instaneous smoothed gains applied to the left and right channels. currentGainL,R exponentially approach gainL,R with a time constant equal to smoothingTime. Note: we have only one time constant controlling both left and right channels. currentGainL,R also serve as the starting point of the module. If currentGainL,R = gainL,R then the module starts up in a converged state. If currentGain != gain for either left or right channels then currentGain will smoothly vary until the value of gain is reached.
Type Definition
typedef struct _ModuleBalanceFract32
{
ModuleInstanceDescriptor instance; // Common Audio Weaver module instance structure
FLOAT32 balance; // Left/Right Balance
FLOAT32 smoothingTime; // Time constant of the smoothing process
fract32 currentGainLFract32; // Instantaneous gain applied to left channel. This is also the starting gain of the left channel.
fract32 currentGainRFract32; // Instantaneous gain applied to right channel. This is also the starting gain of the right channel.
fract32 smoothingCoeff; // Smoothing coefficient
fract32 gainLFract32; // Target gain left channel
fract32 gainRFract32; // Target gain right channel
} ModuleBalanceFract32Class;Variables
Properties
Name | Type | Usage | isHidden | Default value | Range | Units |
balance | float | parameter | 0 | 0 | -1:1 | linear |
smoothingTime | float | parameter | 0 | 10 | 0:1000 | msec |
currentGainLFract32 | fract32 | state | 0 | 0.707 | 0:0.9999 | linear |
currentGainRFract32 | fract32 | state | 0 | 0.707 | 0:0.9999 | linear |
smoothingCoeff | fract32 | derived | 1 | 0.002081 | Unrestricted | Â |
gainLFract32 | fract32 | derived | 1 | 0.7071 | 0:0.9999 | linear |
gainRFract32 | fract32 | derived | 1 | 0.7071 | 0:0.9999 | linear |
Pins
Input Pins
Name: in1
Description: audio input
Data type: fract32
Channel range: Unrestricted
Block size range: Unrestricted
Sample rate range: Unrestricted
Complex support: Real
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Name: in2
Description: audio input
Data type: fract32
Channel range: Unrestricted
Block size range: Unrestricted
Sample rate range: Unrestricted
Complex support: Real
Output Pins
Name: out1
Description: audio output
Data type: fract32
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Name: out2
Description: audio output
Data type: fract32
MATLAB Usage
File Name: balance_fract32_module.m
M=balance_fract32_module(NAME)
Creates a Fractional balance module for use in the
Audio Engine. The module has two multichannel inputs and two
multichannel stereo outputs. Each channel is scaled according to
the value of a balance parameter.
Arguments:
NAME - name of the module.Â