opus-media-recorder

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• JS Fiddle example

opus-media-recorder is a MediaRecorder API polyfill written in ES6 and WebAssembly. It aims for cross-browser Opus codec support with various audio formats such as Ogg and WebM. opus-media-recorder can be used as a polyfill, or it can replace the built-in MediaRecorder since opus-media-recorder supports more MIME types.

opus-media-recorder uses WebAssembly compiled from popular libraries (e.g libopus, libogg, libwebm, and speexdsp) to ensure good performance and standards-compliance.

• Why opus-media-recorder?
• How to use
  • Thing to know
  • JavaScript
    • Examples
    • Installation
    • Working with a bundler
    • Simple JavaScript example (webpack)
  • HTML <script> tag
  • Use opus-media-recorder only when a browser doesn't support it
• Browser support
• MIME Type support
• Limitations
• How to build
• Changelog

Why opus-media-recorder?

	opus-media-recorder	Chrome	Firefox	iOS	Edge
audio/ogg	O	X	O	X	X
audio/webm	O	O	X	X	X
audio/wav	O	X	X	X	X

* Both audio/ogg and audio/webm refer containers for Opus audio codec.

Currently the MediaRecorder API suffers from the two problems:

1. Not all browsers support MediaRecorder.
2. Even the browsers that provides MediaRecorder don't support the same format.

opus-media-recorder tackles these problems by supporting all major modern browsers (Chrome, Firefox, iOS, and Edge) and by providing various formats.

By taking advantages of WebAssembly and Web Workers, opus-media-recorder tries to have minimum performace penalties of running encoders in a browser.

How to use

opus-media-recorder is compatible with the Mediastream Recording API standard.

Thing to know

• The page must be served over HTTPS in order to record.
• Being able to record does not always mean you can play it in a browser:
  • macOS/iOS Safari cannot play Opus natively yet.
  • Old Edge requires an extension to play Opus natively.
  • You can get an Opus decorder to play it. There are Opus decoders available, such as Chris Rudmin's Opus decoder.
  • Otherwise, users can download as a recording file and play it using apps like VLC.
• When mimeType is not specified a default encoder is loaded depending on OS:
  • Chrome: audio/webm
  • Firefox: audio/ogg
  • Edge: audio/webm
  • iOS/macOS Safari: audio/wave - because they cannot play Opus at all.

JavaScript

For standard usages of MediaRecorder, see the MDN reference and other online resources. Our testing website and example section may be useful as well.

Examples

• Webpack
• create-react-app
• Rollup
• Browserify

Installation

1npm install --save-dev opus-media-recorder

Working with a bundler

Because opus-media-recorder needs to load a dedicated web worker and .wasm binaries, special configurations are necessary. In general:

1import OpusMediaRecorder from 'opus-media-recorder';
2// Choose desired format like audio/webm. Default is audio/ogg
3const options = { mimeType: 'audio/ogg' }
4// Web worker and .wasm configuration. Note: This is NOT a part of W3C standard.
5const workerOptions = {
6  encoderWorkerFactory: function () {
7    // UMD should be used if you don't use a web worker bundler for this.
8    return new Worker('.../path/to/opus-media-recorder/encoderWorker.umd.js')
9  },
10  OggOpusEncoderWasmPath: '.../path/to/opus-media-recorder/OggOpusEncoder.wasm',
11  WebMOpusEncoderWasmPath: '.../path/to/opus-media-recorder/WebMOpusEncoder.wasm'
12};
13
14window.MediaRecorder = OpusMediaRecorder;
15recorder = new MediaRecorder(stream, options, workerOptions);

Simple JavaScript example (webpack)

1import MediaRecorder from 'opus-media-recorder';
2// Use worker-loader
3import EncoderWorker from 'worker-loader!opus-media-recorder/encoderWorker.js';
4// You should use file-loader in webpack.config.js.
5// See webpack example link in the above section for more detail.
6import OggOpusWasm from 'opus-media-recorder/OggOpusEncoder.wasm';
7import WebMOpusWasm from 'opus-media-recorder/WebMOpusEncoder.wasm';
8
9// Non-standard options
10const workerOptions = {
11  encoderWorkerFactory: _ => new EncoderWorker(),
12  OggOpusEncoderWasmPath: OggOpusWasm,
13  WebMOpusEncoderWasmPath: WebMOpusWasm
14};
15
16let recorder;
17
18function startRecording () {
19  navigator.mediaDevices.getUserMedia({ audio: true }).then(stream => {
20    let options = { mimeType: 'audio/ogg' };
21    // Start recording
22    recorder = new MediaRecorder(stream, options, workerOptions);
23    recorder.start();
24    // Set record to <audio> when recording will be finished
25    recorder.addEventListener('dataavailable', (e) => {
26      audioElement.src = URL.createObjectURL(e.data);
27    });
28  });
29}
30
31// Recording should be started in user-initiated event like buttons
32recordButton.addEventListener('click', startRecording);
33
34// Stop recording
35stopButton.addEventListener('click', () => {
36  recorder.stop();
37  // Remove “recording” icon from browser tab
38  recorder.stream.getTracks().forEach(i => i.stop());
39})

HTML <script> tag

The OpusMediaRecorder object is available in the global namespace using UMD.

1<!-- load OpusMediaRecorder.umd.js. OpusMediaRecorder will be loaded. -->
2<script src="https://cdn.jsdelivr.net/npm/opus-media-recorder@latest/OpusMediaRecorder.umd.js"></script>
3<!-- load encoderWorker.umd.js. This should be after OpusMediaRecorder. -->
4<!-- This script tag will create OpusMediaRecorder.encoderWorker. -->
5<script src="https://cdn.jsdelivr.net/npm/opus-media-recorder@latest/encoderWorker.umd.js"></script>
6
7<script>
8...
9// If you already load encoderWorker.js using <script> tag,
10// you don't need to define encoderWorkerFactory.
11const workerOptions = {
12  OggOpusEncoderWasmPath: 'https://cdn.jsdelivr.net/npm/opus-media-recorder@latest/OggOpusEncoder.wasm',
13  WebMOpusEncoderWasmPath: 'https://cdn.jsdelivr.net/npm/opus-media-recorder@latest/WebMOpusEncoder.wasm'
14};
15
16// Replace MediaRecorder
17window.MediaRecorder = OpusMediaRecorder;
18let recorder = new MediaRecorder(stream, {}, workerOptions);
19...
20</script>

Use opus-media-recorder only when a browser doesn't support it

1// Check if MediaRecorder available.
2if (!window.MediaRecorder) {
3  window.MediaRecorder = OpusMediaRecorder;
4}
5// Check if a target format (e.g. audio/ogg) is supported.
6else if (!window.MediaRecorder.isTypeSupported('audio/ogg;codecs=opus')) {
7  window.MediaRecorder = OpusMediaRecorder;
8}

Browser support

Supported:

• Chrome >= 58
• Firefox >= 53
• Microsoft Edge >= 41
• Safari (macOS and iOS) >= 11

Browsers with issues:

• iOS 11.2 only: Not working due to a regression in WebAssembly: https://bugs.webkit.org/show_bug.cgi?id=181781

MIME Type support

• audio/webm
• audio/webm; codecs=opus
• audio/ogg
• audio/ogg; codecs=opus
• audio/wav or audio/wave

Limitations

• Does not support Video recording.
• opus-media-recorder throws generic Error objects instead of native DOMException.
• Because audio/wav is not designed for streaming, when mimeType is audio/wav, each dataavailabe events produces a complete and separated .wav file that cannot be concatenated together unlike Ogg and WebM. Therefore, it is recommended not to use timeslice option when calling start(), unless you know what the implication is.
• There is no SecurityError case implemented. (WIP)

How to build

1. To build from the source, you need Emscripten, yarn, Python 2.7 or higher, and basic C program build systems such as GNU Make.

2. yarn install to install JavaScript dependencies.

3. yarn run build to build. yarn run build:production to build files for distribution.

4. yarn run serve to run a test web server locally. Default URL is https://localhost:9000 (It has to be HTTPS). You might have to change DEV_SERVER_URL and DEV_SERVER_PORT to change the address of the local test server.

5. yarn run clean to clean up build files.

Changelog

See CHANGELOG.md.