GainNode.md

GainNode

Namespace: SpawnDev.SpawnJS.JSObjects
Inheritance: SpawnJSObject -> EventTarget -> AudioNode -> GainNode
MDN Reference: GainNode

The GainNode class represents a change in volume. It is an AudioNode that applies a given gain (volume multiplier) to the input audio before passing it to the output. A GainNode always has exactly one input and one output, both with the same number of channels. The gain is a unitless value that is multiplied to each sample of all input channels. To avoid audible clicks when changing volume, use the AudioParam automation methods (LinearRampToValueAtTime, ExponentialRampToValueAtTime, SetTargetAtTime) instead of setting Gain.Value directly.

Constructors

Signature	Description
GainNode(BaseAudioContext context, GainNodeOptions? options = null)	Creates a new GainNode in the given audio context with optional initial gain value.
GainNode(SpawnJSObjectReference _ref)	Deserialization constructor.

Properties

Property	Type	Description
Gain	AudioParam	An a-rate AudioParam representing the amount of gain to apply. Default value is 1.0 (no change). A value of 0 silences the audio; 2.0 doubles the volume.

Inherited Properties (from AudioNode)

Property	Type	Description
Context	BaseAudioContext	The associated audio context.
NumberOfInputs	int	Always 1 for GainNode.
NumberOfOutputs	int	Always 1 for GainNode.
ChannelCount	int	Number of channels.
ChannelCountMode	string	Channel matching mode.
ChannelInterpretation	string	Channel interpretation mode.

AudioParam Methods (on Gain property)

The Gain property is an AudioParam with these scheduling methods:

Method	Return Type	Description
SetValueAtTime(float value, double startTime)	AudioParam	Schedules an instant change at a precise time.
LinearRampToValueAtTime(float value, double endTime)	AudioParam	Schedules a gradual linear change.
ExponentialRampToValueAtTime(float value, double endTime)	AudioParam	Schedules a gradual exponential change (value must be positive).
SetTargetAtTime(float target, double startTime, float timeConstant)	AudioParam	Starts an exponential approach to a target value.
SetValueCurveAtTime(float[] values, double startTime, double duration)	AudioParam	Follows a curve of values over a duration.
CancelScheduledValues(double startTime)	AudioParam	Cancels all scheduled changes from the given time onward.
CancelAndHoldAtTime(double cancelTime)	AudioParam	Cancels scheduled changes but holds the current computed value.

Example

using var audioCtx = new AudioContext();
await audioCtx.Resume();

// Create a gain node using the factory method
using var gain = audioCtx.CreateGain();
gain.Gain.Value = 0.5f; // 50% volume

// Or create using the constructor
using var gain2 = new GainNode(audioCtx, new GainNodeOptions { Gain = 0.8f });

// Build a simple audio graph: Oscillator -> Gain -> Destination
using var oscillator = audioCtx.CreateOscillator();
oscillator.Frequency.Value = 440;

oscillator.Connect(gain);
gain.Connect(audioCtx.Destination);
oscillator.Start();

// Smooth volume fade-in over 2 seconds (avoids clicks)
gain.Gain.SetValueAtTime(0, (float)audioCtx.CurrentTime);
gain.Gain.LinearRampToValueAtTime(1.0f, (float)(audioCtx.CurrentTime + 2.0));

// Smooth fade-out over 1 second, starting 3 seconds from now
gain.Gain.SetValueAtTime(1.0f, (float)(audioCtx.CurrentTime + 3.0));
gain.Gain.ExponentialRampToValueAtTime(0.01f, (float)(audioCtx.CurrentTime + 4.0));

// Create a tremolo effect using LFO modulation
using var lfo = audioCtx.CreateOscillator();
using var lfoGain = audioCtx.CreateGain();

lfo.Frequency.Value = 5;     // 5 Hz tremolo rate
lfoGain.Gain.Value = 0.5f;   // Tremolo depth

lfo.Connect(lfoGain);
lfoGain.Connect(gain.Gain);  // Modulate the main gain
lfo.Start();

// Volume control slider
void SetVolume(float volume)
{
    // Use SetTargetAtTime for smooth transitions
    gain.Gain.SetTargetAtTime(volume, (float)audioCtx.CurrentTime, 0.05f);
}

// Mute (smooth)
SetVolume(0);

// Unmute to 75%
SetVolume(0.75f);