This version (18 May 2021 08:39) was approved by John Joseph.The Previously approved version (18 Mar 2021 02:20) is available.Diff

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Automatic Volume Control


This algorithm is intended for TV sound applications. The perceived volume level often changes considerably from channel to channel, and also within a channel, especially for commercials. This algorithm will automatically compensate for the different levels.


This algorithm supports growing the input channels for 5.1/7.1 applications. However, the volume detection is calculated from the first 2 inputs only (left and right) and the resulting level compensation and delay is applied to all other channels.

Targets Supported

Name ADSP-214xx ADSP-215xx/SC5xx ADAU145x/146x
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Name Type Description
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Input0 Audio First input channel
Input1 Audio Second input channel


Name Type Description
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Output0 Audio First output channel
Output1 Audio

Configurable Parameters

GUI Parameter Default Value Range Function Description
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Enable Off On or Off Turns the processing on and off. This is a bypass switch; changing its position will immediately affect the output signal
DecayRate 4 sec 0.02 - 12 Controls the time to bring a low signal upward to the target level
MaxAttenuation 18 11 - 18 The maximum attenuation that will be applied to a loud signal as the algorithm attempts to maintain a target output level
OutputLevel -18 -18 - -3 The target output level (in RMS) that the algorithm will try to maintain
MaxGain 12 0 - 15 The maximum gain that will be applied to a quiet signal as the algorithm attempts to maintain a target output level
FreezeLevel -36 -36 - -20 The threshold below which the algorithm considers a signal to be “noise” that is not suitable for amplification. When the audio input goes below this level, the output gain will remain unchanged. This effectively lets the algorithm ignore background noise when the main signal of interest is not present. Note that, there is a slow 'Decay Rate' of 12 seconds for the envelope below the freeze level
SideChainFilter B-Weighting Filter Side chain filter selected

DSP Parameters

Parameter Name Description ADAU145x/146x
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hp1_b1 Filter Coefficient 8.24 Format
hp1_b0 Filter Coefficient 8.24 Format
hp1_a1 Filter Coefficient 8.24 Format
hp2_b1 Filter Coefficient 8.24 Format
hp2_b0 Filter Coefficient 8.24 Format
hp2_a1 Filter Coefficient 8.24 Format
lp_b1 Filter Coefficient 8.24 Format
lp_b0 Filter Coefficient 8.24 Format
lp_a1 Filter Coefficient 8.24 Format
Decay Decay coefficient 8.24 Format
attack_rate Attack coefficient 8.24 Format Array
n10 Integer
nm1 Integer
Freeze Freeze 8.24 Format
Decay_Freeze Freeze Decay 8.24 Format
Output_Level_db Output level 8.24 Format
Max_Atten_db Max attenuation 8.24 Format
Max_Gain_db Max gain 8.24 Format
gain_target Target gain 8.24 Format
alpha alpha 8.24 Format
om_alpha 1-alpha 8.24 Format
smooth Smoothing coefficient 8.24 Format

resources/tools-software/sigmastudiov2/modules/adialgorithms/avc.txt · Last modified: 13 May 2021 06:23 by John Joseph