audio volume

AudioVolume

#example #audio #query #threading #simple

Multi-channel audio gain control with mute.

Module Name	audio volume
Type	mtSimple
Color	clAudioModuleColor
Source	examples/AudioVolume/

Description

A multi-channel audio volume module with a gain fader and mute switch. Demonstrates the audio query system for dynamic channel counts and thread-safe parameter handling with std::atomic.

Parameters

Dynamic parameter count based on audio query (N = number of channels):

#	Name	Type	I/O	Details
0..N-1	in 1, in 2, ...	ptAudio	Input	Audio inputs (separator: "audio in")
N..2N-1	out 1, out 2, ...	ptAudio	Output (ReadOnly)	Audio outputs (separator: "audio out")
2N	gain	ptGainFader	Input	Volume fader in dB (separator: "Volume")
2N+1	mute	ptLeftLed	Input	Mute toggle LED

How It Works

1. Audio Query: On creation, Usine shows a popup asking the user how many channels. Uses sdkGetAudioQueryTitle() and sdkGetAudioQueryChannelList().
2. onCallBack: Computes coeffGain = dBtoCoeff(gain) * (1 - mute) and stores it in a std::atomic<float> for thread safety.
3. onProcess: For each channel, copies input to output and multiplies by the gain coefficient.

Key Concepts Demonstrated

• Audio query system for dynamic multi-channel support
• std::atomic<float> for thread-safe parameter sharing between onCallBack and onProcess
• ptGainFader parameter type with dB scaling
• ptLeftLed as a mute toggle
• CanBeSavedInPreset = FALSE — excluding module from preset system
• Separator labels for parameter grouping

Code Pattern: Audio Query

void onGetModuleInfo(TMasterInfo*, TModuleInfo* pModuleInfo) override
{
    pModuleInfo->QueryListString = sdkGetAudioQueryTitle();
    pModuleInfo->QueryListValues = sdkGetAudioQueryChannelList();
    pModuleInfo->QueryListDefaultIdx = 1;
}

int onGetNumberOfParams(int QIdx1, int QIdx2) override
{
    numOfAudioInsOuts = sdkGetAudioQueryToNbChannels(QIdx1);
    return numOfAudioInsOuts * 2 + 2;  // ins + outs + gain + mute
}

SDK Callbacks Used

onGetModuleInfo · onGetNumberOfParams · onAfterQuery · onInitModule · onGetParamInfo · onCallBack · onProcess

Related Examples

• RingMod — Another multi-channel audio module
• Reverb — Complex multi-channel audio processing

SDK Reference

• UserModuleBase Class
• UsineEventClass
• Module Architecture