The AudioBuffer
interface represents a short audio asset residing in memory, created from an audio file using the AudioContext.decodeAudioData()
method, or from raw data using AudioContext.createBuffer()
. Once put into an AudioBuffer, the audio can then be played by being passed into an AudioBufferSourceNode
.
Objects of these types are designed to hold small audio snippets, typically less than 45 s. For longer sounds, objects implementing the MediaElementAudioSourceNode
are more suitable. The buffer contains data in the following format: non-interleaved IEEE754 32-bit linear PCM with a nominal range between -1
and +1
, that is, 32bits floating point buffer, with each samples between -1.0 and 1.0. If the AudioBuffer
has multiple channels, they are stored in separate buffer.
Constructor
AudioBuffer()
- Creates and returns a new
AudioBuffer
object instance.
Properties
AudioBuffer.sampleRate
Read only- Returns a float representing the sample rate, in samples per second, of the PCM data stored in the buffer.
AudioBuffer.length
Read only- Returns an integer representing the length, in sample-frames, of the PCM data stored in the buffer.
AudioBuffer.duration
Read only- Returns a double representing the duration, in seconds, of the PCM data stored in the buffer.
AudioBuffer.numberOfChannels
Read only- Returns an integer representing the number of discrete audio channels described by the PCM data stored in the buffer.
Methods
AudioBuffer.getChannelData()
- Returns a
Float32Array
containing the PCM data associated with the channel, defined by thechannel
parameter (with0
representing the first channel). AudioBuffer.copyFromChannel()
- Copies the samples from the specified channel of the
AudioBuffer
to thedestination
array. AudioBuffer.copyToChannel()
- Copies the samples to the specified channel of the
AudioBuffer
, from thesource
array.
Example
The following simple example shows how to create an AudioBuffer
and fill it with random white noise. You can find the full source code at our webaudio-examples repository; a running live version is also available.
var audioCtx = new (window.AudioContext || window.webkitAudioContext)(); // Create an empty three-second stereo buffer at the sample rate of the AudioContext var myArrayBuffer = audioCtx.createBuffer(2, audioCtx.sampleRate * 3, audioCtx.sampleRate); // Fill the buffer with white noise; // just random values between -1.0 and 1.0 for (var channel = 0; channel < myArrayBuffer.numberOfChannels; channel++) { // This gives us the actual array that contains the data var nowBuffering = myArrayBuffer.getChannelData(channel); for (var i = 0; i < myArrayBuffer.length; 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();
Specifications
Specification | Status | Comment |
---|---|---|
Web Audio API The definition of 'AudioBuffer' in that specification. |
Working Draft | Initial definition. |
Browser compatibility
Desktop | Mobile | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
AudioBuffer | Chrome Full support 14 | Edge Full support ≤18 | Firefox Full support 25 | IE No support No | Opera Full support 15 | Safari Full support 6 | WebView Android Full support Yes | Chrome Android Full support 18 | Firefox Android Full support 26 | Opera Android Full support 14 | Safari iOS Full support Yes | Samsung Internet Android Full support 1.0 |
AudioBuffer() constructor | Chrome
Full support
55
| Edge Full support ≤79 | Firefox Full support 53 | IE No support No | Opera
Full support
42
| Safari ? | WebView Android
Full support
55
| Chrome Android
Full support
55
| Firefox Android Full support 53 | Opera Android
Full support
42
| Safari iOS ? | Samsung Internet Android
Full support
6.0
|
copyFromChannel | Chrome Full support 14 | Edge Full support 13 | Firefox Full support 25 | IE No support No | Opera Full support 15 | Safari Full support 6 | WebView Android Full support Yes | Chrome Android Full support 18 | Firefox Android Full support 26 | Opera Android Full support 14 | Safari iOS ? | Samsung Internet Android Full support 1.0 |
copyToChannel | Chrome Full support 14 | Edge Full support 13 | Firefox Full support 25 | IE No support No | Opera Full support 15 | Safari Full support 6 | WebView Android Full support Yes | Chrome Android Full support 18 | Firefox Android Full support 26 | Opera Android Full support 14 | Safari iOS ? | Samsung Internet Android Full support 1.0 |
duration | Chrome Full support 14 | Edge Full support 12 | Firefox Full support 25 | IE No support No | Opera Full support 15 | Safari Full support 6 | WebView Android Full support Yes | Chrome Android Full support 18 | Firefox Android Full support 26 | Opera Android Full support 14 | Safari iOS Full support Yes | Samsung Internet Android Full support 1.0 |
getChannelData | Chrome Full support 14 | Edge Full support 12 | Firefox Full support 25 | IE No support No | Opera Full support 15 | Safari Full support 6 | WebView Android Full support Yes | Chrome Android Full support 18 | Firefox Android Full support 26 | Opera Android Full support 14 | Safari iOS Full support Yes | Samsung Internet Android Full support 1.0 |
length | Chrome Full support 14 | Edge Full support 12 | Firefox Full support 25 | IE No support No | Opera Full support 15 | Safari Full support 6 | WebView Android Full support Yes | Chrome Android Full support 18 | Firefox Android Full support 26 | Opera Android Full support 14 | Safari iOS Full support Yes | Samsung Internet Android Full support 1.0 |
numberOfChannels | Chrome Full support 14 | Edge Full support 12 | Firefox Full support 25 | IE No support No | Opera Full support 15 | Safari Full support 6 | WebView Android Full support Yes | Chrome Android Full support 18 | Firefox Android Full support 26 | Opera Android Full support 14 | Safari iOS Full support Yes | Samsung Internet Android Full support 1.0 |
sampleRate | Chrome Full support 14 | Edge Full support 12 | Firefox Full support 25 | IE No support No | Opera Full support 15 | Safari Full support 6 | WebView Android Full support Yes | Chrome Android Full support 18 | Firefox Android Full support 26 | Opera Android Full support 14 | Safari iOS Full support Yes | Samsung Internet Android Full support 1.0 |
Legend
- Full support
- Full support
- No support
- No support
- Compatibility unknown
- Compatibility unknown
- See implementation notes.
- See implementation notes.