npm package: @ng-web-apis/audio
Description: This is a library for declarative use of Web Audio API with Angular
Author: Alex Inkin
Latest version: 5.2.0

# ![ng-web-apis logo](https://raw.githubusercontent.com/taiga-family/ng-web-apis/main/libs/audio/logo.svg) Web Audio API for Angular

[![npm version](https://img.shields.io/npm/v/@ng-web-apis/audio.svg)](https://npmjs.com/package/@ng-web-apis/audio)
[![npm bundle size](https://img.shields.io/bundlephobia/minzip/@ng-web-apis/audio)](https://bundlephobia.com/result?p=@ng-web-apis/audio)
[![codecov](https://codecov.io/github/taiga-family/ng-web-apis/graph/badge.svg?flag=audio)](https://codecov.io/github/taiga-family/ng-web-apis/tree/main/libs/audio)

This is a library for declarative use of [Web Audio API](https://developer.mozilla.org/en-US/docs/Web/API/Web_Audio_API)
with Angular 7+. It is a complete conversion to declarative Angular directives, if you find any inconsistencies or
errors, please [file an issue](https://github.com/taiga-family/ng-web-apis/issues). Watch out for 💡 emoji in this
README for additional features and special use cases.

## How to use

> After you installed the package, you **can** add `@ng-web-apis/audio/polyfills` to your `polyfills.ts`. It helps to
> normalize things like `webkitAudioContext`, otherwise your code might fail.

You can build audio graph with directives. For example, here's a typical echo feedback loop:

```html
<audio
  src="/demo.wav"
  waMediaElementAudioSourceNode
>
  <ng-container
    #node="AudioNode"
    waDelayNode
    [delayTime]="delayTime"
  >
    <ng-container
      waGainNode
      [gain]="gain"
    >
      <ng-container [waOutput]="node"></ng-container>
      <ng-container waAudioDestinationNode></ng-container>
    </ng-container>
  </ng-container>
  <ng-container waAudioDestinationNode></ng-container>
</audio>
```

## 💡 WaAudioBufferService

This library has `WaAudioBufferService` with `fetch` method, returning
[Promise](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise) which allows you to
easily turn your hosted audio file into [AudioBuffer](https://developer.mozilla.org/en-US/docs/Web/API/AudioBuffer)
through GET requests. Result is stored in service's cache so same file is not requested again while application is
running.

This service is also used within directives that have
[AudioBuffer](https://developer.mozilla.org/en-US/docs/Web/API/AudioBuffer) inputs (such as
[AudioBufferSourceNode](https://developer.mozilla.org/en-US/docs/Web/API/AudioBufferSourceNode) or
[ConvolverNode](https://developer.mozilla.org/en-US/docs/Web/API/ConvolverNode)) so you can just pass string URL, as
well as an actual [AudioBuffer](https://developer.mozilla.org/en-US/docs/Web/API/AudioBuffer). For example:

```html
<button
  #source="AudioNode"
  buffer="/demo.wav"
  waAudioBufferSourceNode
  (click)="source.start()"
>
  Play
  <ng-container waAudioDestinationNode></ng-container>
</button>
```

## Supported nodes

You can use following audio nodes through directives of the same name (**prefixed with `wa`** standing for Web API):

### Terminal nodes

- [AudioContext](https://developer.mozilla.org/en-US/docs/Web/API/AudioContext)

  💡 Not required if you only need one, global context will be created when needed

  💡 Also gives you access to [AudioListener](https://developer.mozilla.org/en-US/docs/Web/API/AudioListener) parameters
  such as [positionX](https://developer.mozilla.org/en-US/docs/Web/API/AudioListener/positionX)

- [OfflineAudioContext](https://developer.mozilla.org/en-US/docs/Web/API/OfflineAudioContext)

  💡 Additionally supports empty `autoplay` attribute similar to `audio` tag so it would start rendering immediately

  💡 Also gives you access to [AudioListener](https://developer.mozilla.org/en-US/docs/Web/API/AudioListener) parameters
  such as [positionX](https://developer.mozilla.org/en-US/docs/Web/API/AudioListener/positionX)

- [AudioDestinationNode](https://developer.mozilla.org/en-US/docs/Web/API/AudioDestinationNode)

  💡 Use it to terminate branch of your graph

  💡 can be used multiple times inside single
  [BaseAudioContext](https://developer.mozilla.org/en-US/docs/Web/API/BaseAudioContext) referencing the same
  [BaseAudioContext.destination](https://developer.mozilla.org/en-US/docs/Web/API/BaseAudioContext/destination)

  💡 Has `(quiet)` output to watch for particular graph branch going _almost_ silent for 5 seconds straight so you can
  remove branch after all effects played out to silence to free up resources

- [MediaStreamAudioDestinationNode](https://developer.mozilla.org/en-US/docs/Web/API/MediaStreamAudioDestinationNode)

### Sources

- [AudioBufferSourceNode](https://developer.mozilla.org/en-US/docs/Web/API/AudioBufferSourceNode)

  💡 Additionally supports setting URL to media file as
  [buffer](https://developer.mozilla.org/en-US/docs/Web/API/AudioBufferSourceNode/buffer) so it will be fetched and
  turned into [AudioBuffer](https://developer.mozilla.org/en-US/docs/Web/API/AudioBuffer)

  💡 Additionally supports empty `autoplay` attribute similar to `audio` tag so it would start playing immediately

- [ConstantSourceNode](https://developer.mozilla.org/en-US/docs/Web/API/ConstantSourceNode)

  💡 Additionally supports empty `autoplay` attribute similar to `audio` tag so it would start playing immediately

- [MediaElementAudioSourceNode](https://developer.mozilla.org/en-US/docs/Web/API/MediaElementAudioSourceNode)
- [MediaStreamAudioSourceNode](https://developer.mozilla.org/en-US/docs/Web/API/MediaStreamAudioSourceNode)
- [OscillatorNode](https://developer.mozilla.org/en-US/docs/Web/API/OscillatorNode)

  💡 Additionally supports empty `autoplay` attribute similar to `audio` tag so it would start playing immediately

### Processors

- [BiquadFilterNode](https://developer.mozilla.org/en-US/docs/Web/API/BiquadFilterNode)
- [ChannelMergerNode](https://developer.mozilla.org/en-US/docs/Web/API/ChannelMergerNode)

  💡 Use `Channel` directive to merge channels, see example in **Special cases** section

- [ChannelSplitterNode](https://developer.mozilla.org/en-US/docs/Web/API/ChannelSplitterNode)
- [ConvolverNode](https://developer.mozilla.org/en-US/docs/Web/API/ConvolverNode)

  💡 Additionally supports setting URL to media file as
  [buffer](https://developer.mozilla.org/en-US/docs/Web/API/ConvolverNode/buffer) so it will be fetched and turned into
  [AudioBuffer](https://developer.mozilla.org/en-US/docs/Web/API/AudioBuffer)

- [DelayNode](https://developer.mozilla.org/en-US/docs/Web/API/DelayNode)
- [GainNode](https://developer.mozilla.org/en-US/docs/Web/API/GainNode)
- [IIRFilterNode](https://developer.mozilla.org/en-US/docs/Web/API/IIRFilterNode)
- [PannerNode](https://developer.mozilla.org/en-US/docs/Web/API/PannerNode)
- [ScriptProcessorNode](https://developer.mozilla.org/en-US/docs/Web/API/ScriptProcessorNode)
- [StereoPannerNode](https://developer.mozilla.org/en-US/docs/Web/API/StereoPannerNode)
- [WaveShaperNode](https://developer.mozilla.org/en-US/docs/Web/API/WaveShaperNode)

## [AudioWorkletNode](https://developer.mozilla.org/en-US/docs/Web/API/AudioWorkletNode)

You can use [AudioWorkletNode](https://developer.mozilla.org/en-US/docs/Web/API/AudioWorkletNode) in supporting
browsers. To register your
[AudioWorkletProcessors](https://developer.mozilla.org/en-US/docs/Web/API/AudioWorkletProcessor) in a global default
[AudioContext](https://developer.mozilla.org/en-US/docs/Web/API/AudioContext) you can use tokens:

```ts
@NgModule({
  bootstrap: [AppComponent],
  declarations: [AppComponent],
  providers: [
    {
      provide: WA_AUDIO_WORKLET_PROCESSORS,
      useValue: 'assets/my-processor.js',
      multi: true,
    },
  ],
})
export class AppModule {}
```

```ts
@Component({
  selector: 'app',
  templateUrl: './app.component.html',
})
export class App {
  constructor(@Inject(WA_AUDIO_WORKLET_PROCESSORS_READY) readonly processorsReady: Promise<boolean>) {}

  // ...
}
```

You can then instantiate your [AudioWorkletNode](https://developer.mozilla.org/en-US/docs/Web/API/AudioWorkletNode):

```html
<ng-container
  *ngIf="processorsReady | async"
  waAudioWorkletNode
  name="my-processor"
>
  <ng-container waAudioDestinationNode></ng-container>
</ng-container>
```

If you need to create your own node with custom
[AudioParam](https://developer.mozilla.org/en-US/docs/Web/API/AudioParam) and control it declaratively you can extend
`WaWorklet` class and add `audioParam` decorator to new component's inputs:

```ts
@Directive({
  selector: '[my-worklet-node]',
  inputs: ['paramSetter: param'],
  exportAs: 'AudioNode',
  providers: [asAudioNode(MyWorklet)],
})
export class MyWorklet extends WaWorklet {
  set paramSetter(value: AudioParamInput) {
    audioParam(this.param, value, this.context.currentTime);
  }
}
```

## 💡 [AudioParam](https://developer.mozilla.org/en-US/docs/Web/API/AudioParam)

Since work with [AudioParam](https://developer.mozilla.org/en-US/docs/Web/API/AudioParam) is imperative in its nature,
there are difference to native API when working with declarative inputs and directives.

> **NOTE**: You can always access directives through
> [template reference variables](https://angular.io/guide/template-syntax#ref-var) /
> [@ViewChild](https://angular.io/api/core/ViewChild) and since they extend native nodes work with
> [AudioParam](https://developer.mozilla.org/en-US/docs/Web/API/AudioParam) in traditional Web Audio fashion

[AudioParam](https://developer.mozilla.org/en-US/docs/Web/API/AudioParam) inputs for directives accept following
arguments:

- `number` to set in instantly, equivalent to setting
  [AudioParam.value](https://developer.mozilla.org/en-US/docs/Web/API/AudioParam/value)
- `AudioParamCurve` to set array of values over given duration, equivalent to
  [AudioParam.setValueCurveAtTime](https://developer.mozilla.org/en-US/docs/Web/API/AudioParam/setValueCurveAtTime)
  called with [AudioContext.currentTime](https://developer.mozilla.org/en-US/docs/Web/API/BaseAudioContext/currentTime)

      export type AudioParamCurve = {
          readonly value: number[];
          readonly duration: number;
      }

- `AudioParamAutomation` to linearly or exponentially ramp to given value starting from
  [AudioContext.currentTime](https://developer.mozilla.org/en-US/docs/Web/API/BaseAudioContext/currentTime)

      export type AudioParamAutomation = {
          readonly value: number;
          readonly duration: number;
          readonly mode: 'instant' | 'linear' | 'exponential';
      };

- `AudioParamAutomation[]` to schedule multiple changes in value, stacking one after another

You can use `waAudioParam` pipe to turn your number values into `AudioParamAutomation` (default mode is `exponential`,
so last argument can be omitted) or number arrays to `AudioParamCurve` (second argument `duration` is in **seconds**):

```html
<ng-container
  waGainNode
  gain="0"
  [gain]="gain | waAudioParam : 0.1 : 'linear'"
></ng-container>
```

This way values would change smoothly rather than abruptly, causing audio artifacts.

**NOTE:** You can set initial value for [AudioParam](https://developer.mozilla.org/en-US/docs/Web/API/AudioParam)
through argument binding combined with dynamic property binding as seen above.

To schedule an audio envelope looking something like this:

![Envelope](https://raw.githubusercontent.com/taiga-family/ng-web-apis/main/libs/audio/envelope.png)

You would need to pass the following array of `AudioParamAutomation` items:

```ts
const envelope = [
  {
    value: 0,
    duration: 0,
    mode: 'instant',
  },
  {
    value: 1,
    duration: ATTACK_TIME,
    mode: 'linear',
  },
  {
    value: SUS,
    duration: DECAY_TIME,
    mode: 'linear',
  },
  {
    value: SUS,
    duration: SUSTAIN_TIME,
    mode: 'instant',
  },
  {
    value: 0,
    duration: RELEASE_TIME,
    mode: 'exponential',
  },
];
```

## 💡 Special cases

- Use `waOutput` directive when you need non-linear graph (see feedback loop example above) or to manually connect
  [AudioNode](https://developer.mozilla.org/en-US/docs/Web/API/AudioNode) to
  [AudioNode](https://developer.mozilla.org/en-US/docs/Web/API/AudioNode) or
  [AudioParam](https://developer.mozilla.org/en-US/docs/Web/API/AudioParam)
- Use `waPeriodicWave` pipe to create [PeriodicWave](https://developer.mozilla.org/en-US/docs/Web/API/PeriodicWave) for
  [OscillatorNode](https://developer.mozilla.org/en-US/docs/Web/API/OscillatorNode)
- All node directives are exported as `AudioNode` so you can use them with
  [template reference variables](https://angular.io/guide/template-syntax#ref-var) (see feedback loop example above)
- Use `waChannel` directive within
  [ChannelMergerNode](https://developer.mozilla.org/en-US/docs/Web/API/ChannelMergerNode) and direct `waOutput`
  directive to it in order to perform channel merging:

```html
<!-- Inverting left and right channel -->
<audio
  src="/demo.wav"
  waMediaElementAudioSourceNode
>
  <ng-container waChannelSplitterNode>
    <ng-container [waOutput]="right"></ng-container>
    <ng-container [waOutput]="left"></ng-container>
  </ng-container>
  <ng-container waChannelMergerNode>
    <ng-container
      #left="AudioNode"
      waChannel
    ></ng-container>
    <ng-container
      #right="AudioNode"
      waChannel
    ></ng-container>
    <ng-container waAudioDestinationNode></ng-container>
  </ng-container>
</audio>
```

## 💡 Tokens

- You can check [Web Audio API](https://developer.mozilla.org/en-US/docs/Web/API/Web_Audio_API) support in current
  browser by injecting `WA_WEB_AUDIO_SUPPORT` token
- You can inject [BaseAudioContext](https://developer.mozilla.org/en-US/docs/Web/API/BaseAudioContext) through
  `WA_AUDIO_CONTEXT` token
- [AudioContext](https://developer.mozilla.org/en-US/docs/Web/API/AudioContext) is created by default with default
  options when token is requested
- You can also provide custom [BaseAudioContext](https://developer.mozilla.org/en-US/docs/Web/API/BaseAudioContext)
  through that token
- Provide `WA_FEEDBACK_COEFFICIENTS` and `WA_FEEDFORWARD_COEFFICIENTS` tokens to be able to create
  [IIRFilterNode](https://developer.mozilla.org/en-US/docs/Web/API/IIRFilterNode)
- Provide `WA_MEDIA_STREAM` token to be able to create
  [MediaStreamAudioSourceNode](https://developer.mozilla.org/en-US/docs/Web/API/MediaStreamAudioSourceNode)
- All node directives provide underlying [AudioNode](https://developer.mozilla.org/en-US/docs/Web/API/AudioNode) as
  `WA_AUDIO_NODE` token
- Use `WA_AUDIO_WORKLET_PROCESSORS` token to declare array of
  [AudioWorkletProcessors](https://developer.mozilla.org/en-US/docs/Web/API/AudioWorkletProcessor) to be added to
  default [AudioContext](https://developer.mozilla.org/en-US/docs/Web/API/AudioContext)
- Inject `WA_AUDIO_WORKLET_PROCESSORS_READY` token to initialize provided
  [AudioWorkletProcessors](https://developer.mozilla.org/en-US/docs/Web/API/AudioWorkletProcessor) loading and watch for
  [Promise](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise) resolution before
  instantiating dependent [AudioWorkletNodes](https://developer.mozilla.org/en-US/docs/Web/API/AudioWorkletNode)

## Browser support

| [<img src="https://raw.githubusercontent.com/alrra/browser-logos/master/src/edge/edge_48x48.png" alt="IE / Edge" width="24px" height="24px" />](http://godban.github.io/browsers-support-badges/) | [<img src="https://raw.githubusercontent.com/alrra/browser-logos/master/src/firefox/firefox_48x48.png" alt="Firefox" width="24px" height="24px" />](http://godban.github.io/browsers-support-badges/) | [<img src="https://raw.githubusercontent.com/alrra/browser-logos/master/src/chrome/chrome_48x48.png" alt="Chrome" width="24px" height="24px" />](http://godban.github.io/browsers-support-badges/) | [<img src="https://raw.githubusercontent.com/alrra/browser-logos/master/src/safari/safari_48x48.png" alt="Safari" width="24px" height="24px" />](http://godban.github.io/browsers-support-badges/) |
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> Note that some features ([AudioWorklet](https://developer.mozilla.org/en-US/docs/Web/API/AudioWorklet) etc.) were
> added later and are supported only by more recent versions

_**IMPORTANT**: You must add `@ng-web-apis/audio/polyfill` to your `polyfills.ts`, otherwise you will get
`ReferenceError: X is not defined` in browsers for entities they do not support_

💡 [StereoPannerNode](https://developer.mozilla.org/en-US/docs/Web/API/StereoPannerNode) is emulated with
[PannerNode](https://developer.mozilla.org/en-US/docs/Web/API/PannerNode) in browsers that do not support it yet

💡 [positionX](https://developer.mozilla.org/en-US/docs/Web/API/AudioListener/positionX)
([orientationX](https://developer.mozilla.org/en-US/docs/Web/API/AudioListener/orientationX)) and other similar
properties of [AudioListener](https://developer.mozilla.org/en-US/docs/Web/API/AudioListener) and
[PannerNode](https://developer.mozilla.org/en-US/docs/Web/API/PannerNode) fall back to
[setPosition](https://developer.mozilla.org/en-US/docs/Web/API/AudioListener/setPosition)
([setOrientation](https://developer.mozilla.org/en-US/docs/Web/API/AudioListener/setOrientation)) method if browser does
not support it

## Angular Universal

If you want to use this package with SSR, you need to mock native Web Audio API classes on the server:

```ts
import '@ng-web-apis/audio/polyfill';
```

> It is recommended to keep the import statement at the top of your `server.ts` or `main.server.ts` file.

## Demo

You can [try online demo here](https://taiga-family.github.io/ng-web-apis/audio)

## See also

Other [Web APIs for Angular](https://taiga-family.github.io/ng-web-apis/) by
[@ng-web-apis](https://github.com/taiga-family/ng-web-apis)