OfflineAudioContext() constructor—part of the Web Audio API—creates and returns a new
OfflineAudioContext object instance, which can then be used to render audio to an
AudioBuffer rather than to an audio output device.
var offlineAudio = new OfflineAudioContext(numOfChannels, length, sampleRate); var offlineAudio = new OfflineAudioContext(options);
You can specify the parameters for the
OfflineAudioContext() constructor as either the same set of parameters as are inputs into the
AudioContext.createBuffer() method, or by passing those parameters in an
options object. Either way, the individual parameters are the same.
- An integer specifying the number of channels the resulting
- An integer specifying the size of the buffer to create for the audio context, in sample-frames, where one sample-frame is a unit that can contain a single sample of audio data for every channel in the audio data. For example, a 512 sample-frame buffer for 8 channels of sound would be
512 * ((sizeof(float32) * 8) * 32)or 524,288 bytes.
- The sample-rate of the linear audio data in sample-frames per second. All user agents are required to support a range of 22050kHz to 96000kHz, and may support a wider range than that. The most commonly-used rate is 44100kHz, which is the sample rate used by CD audio.
It is important to note that, whereas you can create a new
AudioContext using the
new AudioContext() constructor with no arguments, the
OfflineAudioContext() constructor requires three arguments, since it needs to create an
AudioBuffer. This works in exactly the same way as when you create a new
AudioBuffer with the
AudioContext.createBuffer() method. For more detail, read Audio buffers: frames, samples and channels from our Basic concepts guide.
OfflineAudioContext object whose associated
AudioBuffer is configured as requested.
Like a regular
OfflineAudioContext can be the target of events, therefore it implements the
// define online and offline audio context var audioCtx = new AudioContext(); var offlineCtx = new OfflineAudioContext(2, 44100*40, 44100); var source = offlineCtx.createBufferSource(); // etc...
|Web Audio API
The definition of 'OfflineAudioContext' in that specification.
|Parameters accepted as a single object, as well as being passed in individually||62||?||57||No||49||No|
|Feature||Android webview||Chrome for Android||Edge mobile||Firefox for Android||IE mobile||Opera Android||iOS Safari|
|Parameters accepted as a single object, as well as being passed in individually||62||62||?||57||No||49||No|
1. Before Chrome 59, the default values were not supported.