The getChannelData()
method of the AudioBuffer
Interface returns a Float32Array
containing the PCM data associated with the channel, defined by the channel parameter (with 0 representing the first channel).
Syntax
var myArrayBuffer = audioCtx.createBuffer(2, frameCount, audioCtx.sampleRate); var nowBuffering = myArrayBuffer.getChannelData(channel);
Returns
A Float32Array
.
Example
In the following example we create a two second buffer, fill it with white noise, and then play it via an AudioBufferSourceNode
. The comments should clearly explain what is going on. You can also run the code live, or view the source.
var audioCtx = new (window.AudioContext || window.webkitAudioContext)(); var button = document.querySelector('button'); var pre = document.querySelector('pre'); var myScript = document.querySelector('script'); pre.innerHTML = myScript.innerHTML; // Stereo var channels = 2; // Create an empty two second stereo buffer at the // sample rate of the AudioContext var frameCount = audioCtx.sampleRate * 2.0; var myArrayBuffer = audioCtx.createBuffer(2, frameCount, audioCtx.sampleRate); button.onclick = function() { // Fill the buffer with white noise; //just random values between -1.0 and 1.0 for (var channel = 0; channel < channels; channel++) { // This gives us the actual ArrayBuffer that contains the data var nowBuffering = myArrayBuffer.getChannelData(channel); for (var i = 0; i < frameCount; i++) { // Math.random() is in [0; 1.0] // audio needs to be in [-1.0; 1.0] nowBuffering[i] = Math.random() * 2 - 1; } } // Get an AudioBufferSourceNode. // This is the AudioNode to use when we want to play an AudioBuffer var source = audioCtx.createBufferSource(); // set the buffer in the AudioBufferSourceNode source.buffer = myArrayBuffer; // connect the AudioBufferSourceNode to the // destination so we can hear the sound source.connect(audioCtx.destination); // start the source playing source.start(); }
Parameters
- channel
- The channel property is an index representing the particular channel to get data for. An index value of 0 represents the first channel. If the
channel
index value is greater than of equal toAudioBuffer.numberOfChannels
, anINDEX_SIZE_ERR
exception will be thrown.
Specification
Specification | Status | Comment |
---|---|---|
Web Audio API The definition of 'getChannelData' in that specification. |
Working Draft |
Browser compatibility
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari (WebKit) |
---|---|---|---|---|---|
Basic support | 14 webkit | 23 | Not supported | 15 webkit 22 (unprefixed) |
6 webkit |
Feature | Android | Chrome | Firefox Mobile (Gecko) | Firefox OS | IE Phone | Opera Mobile | Safari Mobile |
---|---|---|---|---|---|---|---|
Basic support | Not supported | 28 webkit | 25 | 1.2 | Not supported | Not supported | 6 webkit |
See also
Document Tags and Contributors
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Contributors to this page:
fscholz,
chrisdavidmills
Last updated by:
fscholz,