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.
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
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).
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();
AudioParamyou are connecting to.
- Output (optional)
- An index describing which output of the current
AudioNodeyou want to connect to the
AudioParam. The index numbers are defined according to the number of output channels (see Audio channels.) If this parameter is out-of-bound, an
INDEX_SIZE_ERRexception is thrown.
|Web Audio API
The definition of 'connect(AudioParam)' in that specification.
|Feature||Chrome||Firefox (Gecko)||Internet Explorer||Opera||Safari (WebKit)|
||(Yes) webkit||(Yes)||No support||(Yes)||No support|
|Feature||Android||Firefox Mobile (Gecko)||Firefox OS (Gecko)||IE Phone||Opera Mobile||Safari Mobile|
||No support||(Yes)||(Yes)||No support||No support||No support|
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