The connect
method of the AudioNode
interface allows us to connect one output of the current node to one input of an audio parameter (AudioParam
node), allowing us to control the parameter value with an audio signal.
It is possible to connect an AudioNode
output to more than one AudioParam
, and more than one AudioNode output to a single AudioParam
, with multiple calls to connect()
. Fan-in and fan-out are therefore supported.
An AudioParam
will take the rendered audio data from any AudioNode
output connected to it and convert it to mono by down-mixing (if it is not already mono). Next, it will mix it together with any other such outputs, and the intrinsic parameter value (the value the AudioParam
would normally have without any audio connections), including any timeline changes scheduled for the parameter.
Therefore, it is possible to choose the range in which an AudioParam
will change by setting the value of the AudioParam
to the central frequency, and to use a GainNode
between the audio source and the AudioParam
to adjust the range of the AudioParam
changes:
Syntax
var lfo = audioCtx.createOscillator(); lfo.frequency.value = 2.0; // Hz, two times per second var lfoGain = audioCtx.createGain(); lfoGain.gain.value = 0.5; // this is the parameter that is going to be modulated var gain = audioCtx.createGain(); gain.gain.value = 0.5; // Oscillators go from -1 to 1 // Make it go from -0.5 to +0.5 by connecting it to a GainNode with a gain value of 0.5 lfo.connect(lfoGain); // because the value of the gain.gain AudioParam is originaly 0.5, the value is added, and it will go from 0.0 to 1.0 lfoGain.connect(gain.gain); lfo.connect(gain.gain);
Note: There can only be one connection between an output from one specific AudioNode
and an AudioParam
. Multiple connections to the same termini are equivalent to a single such connection (the duplicates are ignored).
Returns
Void.
Example
In this example, we will be altering the gain value of a GainNode
using an OscillatorNode
with a slow frequency value. This technique is know as an LFO-controlled parameter.
var AudioContext = window.AudioContext || window.webkitAudioContext; var audioCtx = new AudioContext(); // create an normal oscillator to make sound var oscillator = audioCtx.createOscillator(); // create a second oscillator that will be used as an LFO (Low-frequency // oscillator), and will control a parameter var lfo = audioCtx.createOscillator(); // set the frequency of the second oscillator to a low number lfo.frequency.value = 2.0; // 2Hz: two oscillations par second // create a gain whose gain AudioParam will be controlled by the LFO var gain = audioCtx.createGain(); // connect the LFO to the gain AudioParam. This means the value of the LFO // will not produce any audio, but will change the value of the gain instead lfo.connect(gain.gain); // connect the oscillator that will produce audio to the gain oscillator.connect(gain); // connect the gain to the destination so we hear sound gain.connect(audioCtx.destination); // start the oscillator that will produce audio oscillator.start(); // start the oscillator that will modify the gain value lfo.start();
Parameters
- Destination
- The
AudioParam
you are connecting to. - Output (optional)
- An index describing which output of the current
AudioNode
you want to connect to theAudioParam
. The index numbers are defined according to the number of output channels (see Audio channels.) If this parameter is out-of-bound, anINDEX_SIZE_ERR
exception is thrown.
Specifications
Specification | Status | Comment |
---|---|---|
Web Audio API The definition of 'connect(AudioParam)' in that specification. |
Working Draft |
Browser compatibility
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari (WebKit) |
---|---|---|---|---|---|
connect (AudioParam) |
(Yes) webkit | (Yes) | No support | (Yes) | No support |
Feature | Android | Firefox Mobile (Gecko) | Firefox OS (Gecko) | IE Phone | Opera Mobile | Safari Mobile |
---|---|---|---|---|---|---|
connect (AudioParam) |
No support | (Yes) | (Yes) | No support | No support | No support |