Node-style stream for getUserMedia


If you just want to get some audio data from your microphone, this is what you're looking for!

Converts a MediaStream (from getUserMedia) into a standard Node.js-style stream for easy pipe()ing.

Note: This only works in a limited set of browsers
(typically with webpack or browserify),
and then only for https or localhost in Chrome.
It does not work in Node.js.

$3

``js
const getUserMedia = require('get-user-media-promise');
const MicrophoneStream = require('microphone-stream').default;

document.getElementById('my-start-button').onclick = function() {

// Note: in most browsers, this constructor must be called in response to a click/tap,
// or else the AudioContext will remain suspended and will not provide any audio data.
const micStream = new MicrophoneStream();

getUserMedia({ video: false, audio: true })
.then(function(stream) {
micStream.setStream(stream);
}).catch(function(error) {
console.log(error);
});

// get Buffers (Essentially a Uint8Array DataView of the same Float32 values)
micStream.on('data', function(chunk) {
// Optionally convert the Buffer back into a Float32Array
// (This actually just creates a new DataView - the underlying audio data is not copied or modified.)
const raw = MicrophoneStream.toRaw(chunk)
//...

// note: if you set options.objectMode=true, the data event will output AudioBuffers instead of Buffers
});

// or pipe it to another stream
micStream.pipe(/.../);

// Access the internal audioInput for connecting to another nodes
micStream.audioInput.connect(/.../));

// It also emits a format event with various details (frequency, channels, etc)
micStream.on('format', function(format) {
console.log(format);
});

// Stop when ready
document.getElementById('my-stop-button').onclick = function() {
micStream.stop();
};
}


`

API

$3

Where opts is an option object, with defaults:

`js
{
stream: null,
objectMode: false,
bufferSize: null,
context: null
}
`

- stream: MediaStream instance. For iOS compatibility, it is recommended that you create the MicrophoneStream instance in response to the tap - before you have a MediaStream, and then later call setStream() with the MediaStream.

- bufferSize: Possible values: null, 256, 512, 1024, 2048, 4096, 8192, 16384. From Mozilla's Docs:
> It is recommended for authors to not specify this buffer size and allow the implementation to pick a good buffer size
> to balance between latency and audio quality.
- objectMode: if true, stream enters [objectMode] and emits AudioBuffers instead of Buffers. This has implications for pipe()'ing to other streams.

- context is the AudioContext instance. If omitted, one will be created automatically.

#### .setStream(mediaStream)

Set the mediaStream, necessary for iOS 11 support where the underlying AudioContext must be resumed in response to a user tap, but the mediaStream won't be available until later.
Note: Some versions of Firefox leave the recording icon in place after recording has stopped.

#### .stop()

Stops the recording.
Note: Some versions of Firefox leave the recording icon in place after recording has stopped.

#### .pauseRecording()

Temporarily stop emitting new data. Audio data recieved from the microphone after this will be dropped.

Note: the underlying Stream interface has a .pause() API that causes new data to be buffered rather than dropped.

#### .playRecording()

Resume emitting new audio data after pauseRecording() was called.

#### Event: data

Emits either a [Buffer] with raw 32-bit Floating point audio data, or if [objectMode] is set, an [AudioBuffer] containing the data + some metadata.

#### Event: format

One-time event with details of the audio format. Example:

`js
{
channels: 1,
bitDepth: 32,
sampleRate: 48000,
signed: true,
float: true
}
`

MicrophoneStream.toRaw(Buffer) -> Float32Array

Converts a Buffer (from a data event or from calling .read()`) back to the original Float32Array DataView format. (The underlying audio data is not copied or modified.)

[audiobuffer]: https://developer.mozilla.org/en-US/docs/Web/API/AudioBuffer
[buffer]: https://nodejs.org/api/buffer.html
[objectmode]: https://nodejs.org/api/stream.html#stream_object_mode