BaseAudioContext

The BaseAudioContext interface acts as a supervisor of audio-processing graphs. It provides key processing parameters such as current time, output destination or sample rate. Additionally, it is responsible for nodes creation and audio-processing graph's lifecycle management. However, BaseAudioContext itself cannot be directly utilized, instead its functionalities must be accessed through one of its derived interfaces: AudioContext, OfflineAudioContext.

Audio graph

An audio graph is a structured representation of audio processing elements and their connections within an audio context. The graph consists of various types of nodes, each performing specific audio operations, connected in a network that defines the audio signal flow. In general we can distinguish four types of nodes:

Source nodes (e.g AudioBufferSourceNode, OscillatorNode)
Effect nodes (e.g GainNode, BiquadFilterNode)
Analysis nodes (e.g AnalyserNode)
Destination nodes (e.g AudioDestinationNode)

Rendering audio graph

Audio graph rendering is done in blocks of sample-frames. The number of sample-frames in a block is called render quantum size, and the block itself is called a render quantum. By default render quantum size value is 128 and it is constant.

The AudioContext rendering thread is driven by a system-level audio callback. Each call has a system-level audio callback buffer size, which is a varying number of sample-frames that needs to be computed on time before the next system-level audio callback arrives, but render quantum size does not have to be a divisor of the system-level audio callback buffer size.

info

Concept of system-level audio callback does not apply to OfflineAudioContext.

Properties

Name	Type	Description
`currentTime`	`number`	Double value representing an ever-increasing hardware time in seconds, starting from 0.	Read only
`destination`	`AudioDestinationNode`	Final output destination associated with the context.	Read only
`sampleRate`	`number`	Float value representing the sample rate (in samples per seconds) used by all nodes in this context.	Read only
`state`	`ContextState`	Enumerated value represents the current state of the context.	Read only

Methods

`createAnalyser`

Creates AnalyserNode.

Returns `AnalyserNode`.

`createBiquadFilter`

Creates BiquadFilterNode.

Returns `BiquadFilterNode`.

`createBuffer`

Creates AudioBuffer.

Parameter	Type	Description
`numOfChannels`	`number`	An integer representing the number of channels of the buffer.
`length`	`number`	An integer representing the length of the buffer in sampleFrames. Two seconds buffer has length equals to `2 * sampleRate`.
`sampleRate`	`number`	A float representing the sample rate of the buffer.

Errors

Error type	Description
`NotSupportedError`	`numOfChannels` is outside the nominal range [1, 32].
`NotSupportedError`	`sampleRate` is outside the nominal range [8000, 96000].
`NotSupportedError`	`length` is less then 1.

Returns `AudioBuffer`.

`createBufferSource`

Creates AudioBufferSourceNode.

Parameter	Type	Description
`options` Optional	`AudioBufferBaseSourceNodeOptions`	Dictionary object that specifies if pitch correction has to be available.

Returns `AudioBufferSourceNode`.

`createBufferQueueSource`
Mobile only

Creates AudioBufferQueueSourceNode.

Parameter	Type	Description
`options` Optional	`AudioBufferBaseSourceNodeOptions`	Dictionary object that specifies if pitch correction has to be available.

Returns `AudioBufferQueueSourceNode`.

`createConstantSource`

Creates ConstantSourceNode.

Returns `ConstantSourceNode`.

`createConvolver`

Creates ConvolverNode.

Parameter	Type	Description
`options` Optional	`ConvolverNodeOptions`	Dictionary object that specifies associated buffer and normalization.

Errors

Error type	Description
`NotSupportedError`	`numOfChannels` of buffer is not 1, 2 or 4.

Returns `ConvolverNode`.

`createDelay`

Creates DelayNode

Parameter	Type	Description
`maxDelayTime` Optional	`number`	Maximum amount of time to buffer delayed values

Returns `DelayNode`

`createGain`

Creates GainNode.

Returns `GainNode`.

`createIIRFilter`

Creates IIRFilterNode.

Parameter	Type	Description
`options`	`IIRFilterNodeOptions`	Dictionary object that specifies the feedforward (numerator) and feedback (denominator) coefficients for the transfer function of the IIR filter.

Errors

Error type	Description
`NotSupportedError`	One or both of the input arrays exceeds 20 members.
`InvalidStateError`	All of the feedforward coefficients are 0, or the first feedback coefficient is 0.

Returns `IIRFilterNode`.

`createOscillator`

Creates OscillatorNode.

Returns `OscillatorNode`.

`createPeriodicWave`

Creates PeriodicWave. This waveform specifies a repeating pattern that an OscillatorNode can use to generate its output sound.

Parameter	Type	Description
`real`	`Float32Array`	An array of cosine terms.
`imag`	`Float32Array`	An array of sine terms.
`constraints` Optional	`PeriodicWaveConstraints`	An object that specifies if normalization is disabled. If so, periodic wave will have maximum peak value of 1 and minimum peak value of -1.

Errors

Error type	Description
`InvalidAccessError`	`real` and `imag` arrays do not have same length.

Returns `PeriodicWave`.

`createRecorderAdapter`

Creates RecorderAdapterNode.

Returns `RecorderAdapterNode`

`createStereoPanner`

Creates StereoPannerNode.

Returns `StereoPannerNode`.

`createStreamer`
Mobile only

Creates StreamerNode.

Returns `StreamerNode`.

`createWaveShaper`

Creates WaveShaperNode.

Returns `WaveShaperNode`.

`createWorkletNode`
Mobile only

Creates WorkletNode.

Parameter	Type	Description
`worklet`	`(Array<Float32Array>, number) => void`	The worklet to be executed.
`bufferLength`	`number`	The size of the buffer that will be passed to the worklet on each call.
`inputChannelCount`	`number`	The number of channels that the node expects as input (it will get min(expected, provided)).
`workletRuntime`	`AudioWorkletRuntime`	The kind of runtime to use for the worklet. See worklet runtimes for details.

Errors

Error type	Description
`Error`	`react-native-worklet` is not found as dependency.
`NotSupportedError`	`bufferLength` < 1.
`NotSupportedError`	`inputChannelCount` is not in range [1, 32].

Returns `WorkletNode`.

`createWorkletSourceNode`
Mobile only

Creates WorkletSourceNode.

Parameter	Type	Description
`worklet`	`(Array<Float32Array>, number, number, number) => void`	The worklet to be executed.
`workletRuntime`	`AudioWorkletRuntime`	The kind of runtime to use for the worklet. See worklet runtimes for details.

Errors

Error type	Description
`Error`	`react-native-worklet` is not found as dependency.

Returns `WorkletSourceNode`.

`createWorkletProcessingNode`
Mobile only

Creates WorkletProcessingNode.

Parameter	Type	Description
`worklet`	`(Array<Float32Array>, Array<Float32Array>, number, number) => void`	The worklet to be executed.
`workletRuntime`	`AudioWorkletRuntime`	The kind of runtime to use for the worklet. See worklet runtimes for details.

Errors

Error type	Description
`Error`	`react-native-worklet` is not found as dependency.

Returns `WorkletProcessingNode`.

`decodeAudioData`

Decodes audio data from either a file path or an ArrayBuffer. The optional sampleRate parameter lets you resample the decoded audio. If not provided, the audio will be automatically resampled to match the audio context's sampleRate.

For the list of supported formats visit this page.

Parameter	Type	Description
`input`	`ArrayBuffer`	ArrayBuffer with audio data.
	`string`	Path to remote or local audio file.
	`number`	Asset module id. Mobile only
`fetchOptions` Optional	`RequestInit`	Additional headers parameters when passing url to fetch.

Returns `Promise<AudioBuffer>`.

Example decoding with memory block

const url = ... // url to an audio

const buffer = await fetch(url)
  .then((response) => response.arrayBuffer())
  .then((arrayBuffer) => this.audioContext.decodeAudioData(arrayBuffer))
  .catch((error) => {
    console.error('Error decoding audio data source:', error);
    return null;
  });

Example using expo-asset library

import { Asset } from 'expo-asset';

const buffer = await Asset.fromModule(require('@/assets/music/example.mp3'))
    .downloadAsync()
    .then((asset) =>  {
      if (!asset.localUri) {
        throw new Error('Failed to load audio asset');
      }
      return this.audioContext.decodeAudioData(asset.localUri);
    })

`decodePCMInBase64`

Decodes base64-encoded PCM audio data.

Parameter	Type	Description
`base64String`	`string`	Base64-encoded PCM audio data.
`inputSampleRate`	`number`	Sample rate of the input PCM data.
`inputChannelCount`	`number`	Number of channels in the input PCM data.
`isInterleaved` Optional	`boolean`	Whether the PCM data is interleaved. Default is `true`.

Returns `Promise<AudioBuffer>`

Example decoding with data in base64 format

const data = ... // data encoded in base64 string
// data is not interleaved (Channel1, Channel1, ..., Channel2, Channel2, ...)
const buffer = await this.audioContext.decodeAudioData(data, 4800, 2, false);

Remarks

`currentTime`

Timer starts when context is created, stops when context is suspended.

`ContextState`

Details

Acceptable values:

suspended

The audio context has been suspended (with one of suspend or OfflineAudioContext.suspend).

running

The audio context is running normally.

closed

The audio context has been closed (with close method).

Audio graph​

Rendering audio graph​

Properties​

Methods​

createAnalyser​

Returns AnalyserNode.​

createBiquadFilter​

Returns BiquadFilterNode.​

createBuffer​

Errors​

Returns AudioBuffer.​

createBufferSource​

Returns AudioBufferSourceNode.​

createBufferQueueSource Mobile only​

Returns AudioBufferQueueSourceNode.​

createConstantSource​

Returns ConstantSourceNode.​

createConvolver​

Errors​

Returns ConvolverNode.​

createDelay​

Returns DelayNode​

createGain​

Returns GainNode.​

createIIRFilter​

Errors​

Returns IIRFilterNode.​

createOscillator​

Returns OscillatorNode.​

createPeriodicWave​

Errors​

Returns PeriodicWave.​

createRecorderAdapter​

Returns RecorderAdapterNode​

createStereoPanner​

Returns StereoPannerNode.​

createStreamer Mobile only​

Returns StreamerNode.​

createWaveShaper​

Returns WaveShaperNode.​

createWorkletNode Mobile only​

Errors​

Returns WorkletNode.​

createWorkletSourceNode Mobile only​

Errors​

Returns WorkletSourceNode.​

createWorkletProcessingNode Mobile only​

Errors​

Returns WorkletProcessingNode.​

decodeAudioData​

Returns Promise<AudioBuffer>.​

decodePCMInBase64​

Returns Promise<AudioBuffer>​

Remarks​

currentTime​

ContextState​

Audio graph

Rendering audio graph

Properties

Methods

`createAnalyser`

Returns `AnalyserNode`.

`createBiquadFilter`

Returns `BiquadFilterNode`.

`createBuffer`

Errors

Returns `AudioBuffer`.

`createBufferSource`

Returns `AudioBufferSourceNode`.

`createBufferQueueSource`
Mobile only

Returns `AudioBufferQueueSourceNode`.

`createConstantSource`

Returns `ConstantSourceNode`.

`createConvolver`

Errors

Returns `ConvolverNode`.

`createDelay`

Returns `DelayNode`

`createGain`

Returns `GainNode`.

`createIIRFilter`

Errors

Returns `IIRFilterNode`.

`createOscillator`

Returns `OscillatorNode`.

`createPeriodicWave`

Errors

Returns `PeriodicWave`.

`createRecorderAdapter`

Returns `RecorderAdapterNode`

`createStereoPanner`

Returns `StereoPannerNode`.

`createStreamer`
Mobile only

Returns `StreamerNode`.

`createWaveShaper`

Returns `WaveShaperNode`.

`createWorkletNode`
Mobile only

Errors

Returns `WorkletNode`.

`createWorkletSourceNode`
Mobile only

Errors

Returns `WorkletSourceNode`.

`createWorkletProcessingNode`
Mobile only

Errors

Returns `WorkletProcessingNode`.

`decodeAudioData`

Returns `Promise<AudioBuffer>`.

`decodePCMInBase64`

Returns `Promise<AudioBuffer>`

Remarks

`currentTime`

`ContextState`