audio_worklet

A plugin to stream blocks of audio to the sound card.

This plugin was created to mimic the way the ScriptProcessingNode of the Web Audio API works. After the sound card is started, the sound system make a periodic callback to request the next block of audio samples. The callback is implemented as a Native->Dart callback, and must be provided by implementing AWEvents.

The use of a callback allows the Flutter application to generate the audio on the fly from a signal generator, midi player, audio codec, pitch changer, jitter buffer, etc, etc.

Usage

A typical first use is to query the default sample rate of the sound system.

import 'package:audio_worklet/audio_worklet.dart';

var nativeRate = await AudioWorklet.nativeRate;

To start the sound card use start(rate) and to stop it use stop(). For example:

              RaisedButton(
                child: Text('Start'),
                onPressed: () => AudioWorklet.start(_nativeRate),
              ),
              RaisedButton(
                child: Text('Stop'),
                onPressed: () => AudioWorklet.stop(),
              ),

In the same way that the Web Audio API works, a callback function must be provided to deliver the next block of audio samples periodically. The Flutter application must implement AWEvents, and pass in that implementation when inititalizing the library. One way is to implement this at the application stateful widget level.

class _MyAppState extends State<MyApp> implements AWEvents {

  @override
  void initState() {
    super.initState();
    AudioWorklet.setEventHandler(this); // register the callback
    initPlatformState();
  }

  @override
  Float64List getAudio() {
    // todo - return a list of double samples between -1.0 and +1.0
  }