wasm-media-encoders
The LAME MP3 and Ogg Vorbis audio encoders, compiled to minimal WebAssembly and ready for use in the browser or Node.
Why?
While some browsers have native encoding using the MediaRecorder
API, it only supports a small number of codecs.
This package aims to fill the gap by compiling the reference LAME and Ogg Vorbis encoders to WebAssembly. The resulting package is tiny and fast:
Encoder | JS* | WASM | Combined + Gzipped |
---|---|---|---|
MP3 | 3.3 KiB | 130 KiB | 66 KiB |
Ogg Vorbis | 3.3 KiB | 440 KiB | 158 KiB |
*When using ESNext syntax and no polyfills
Installation
yarn add wasm-media-encoders
or
npm install wasm-media-encoders
Getting started
With webpack or .mjs
file in Node 12+:
import { createMp3Enoder, createOggEncoder } from "wasm-media-encoders";
createOggEncoder().then((encoder) => {
/* Configure and use the encoder */
});
createMp3Encoder().then((encoder) => {
/* Configure and use the encoder */
});
With a <script>
tag:
<script src="https://unpkg.com/wasm-media-encoders/dist/umd/WasmMediaEncoder.min.js"></script>
<script>
// The UMD package will fetch() the WASM binaries from
// unpkg.com by default to reduce size
WasmMediaEncoder.createMp3Encoder().then((encoder) => {
/* Configure and use the encoder */
});
</script>
Using CommonJS in Node:
const { createMp3Encoder } = require("wasm-media-encoders");
createMp3Encoder().then((encoder) => {
/* Configure and use the encoder */
});
If you'd like to use ESNext syntax and transpile yourself, use the wasm-media-encoders/esnext
path.
Example usage
createMp3Encoder().then((encoder) => {
encoder.configure({
sampleRate: 48000,
channels: 2,
vbrQuality: 2,
});
let outBuffer = new Uint8Array(1024 * 1024);
let offset = 0;
let moreData = true;
while (true) {
const mp3Data = moreData
? encoder.encode([
pcm_l /* Float32Array of left channel PCM data */,
pcm_r /* Float32Array of right channel PCM data */,
])
: /* finalize() returns the last few frames */
encoder.finalize();
/* mp3Data is a Uint8Array that is still owned by the encoder and MUST be copied */
if (mp3Data.length + offset > outBuffer.length) {
const newBuffer = new Uint8Array(mp3Data.length + offset);
newBuffer.set(outBuffer);
outBuffer = newBuffer;
}
outBuffer.set(mp3Data, offset);
offset += mp3Data.length;
if (!moreData) {
break;
}
moreData = false;
}
return new Uint8Array(outBuffer.buffer, 0, offset);
/* Or encoder can be reused without calling createEncoder() again:
encoder.configure({...new params})
encoder.encode()
encoder.finalize() */
});
Reducing bundle size
By default, this package inlines the WASM binary as a base64-encoded data URL. This make importing the encoder easy, but also increases the bundle size by about 30%. With webpack, you can load the WASM directly (found in wasm-media-encoders/wasm/(mp3|ogg).wasm
), passing the URL as the second parameter to createEncoder()
.
Webpack v4
Besides using file-loader
, you also need to disable WASM parsing in the webpack config:
import { createEncoder } from "wasm-media-encoders";
import wasm from "file-loader!wasm-media-encoders/wasm/mp3.wasm";
createEncoder("audio/mpeg", wasm).then((encoder) => {
/* Now mp3.wasm will be copied to output dir by webpack and fetch()ed at runtime */
});
// webpack.config.js
module.exports = {
// ...
module: {
rules: [
{
test: /\.wasm$/,
type: "javascript/auto",
},
],
},
};
Webpack v5
Using asset modules and URL assets is easy in webpack v5:
import { createEncoder } from "wasm-media-encoders";
createEncoder(
"audio/mpeg",
new URL("wasm-media-encoder/wasm/mp3", import.meta.url)
).then((encoder) => {
/* Now mp3.wasm will be copied to output dir by webpack and fetch()ed at runtime */
});
API
Named exports:
createMp3Encoder(): Promise<WasmMediaEncoder>
createOggEncoder(): Promise<WasmMediaEncoder>
createEncoder(mimeType, wasm, moduleCallback?): Promise<WasmMediaEncoder>
The first two named exports use inline base-64 encoded WASM binaries (or fetch()
from unpkg.com in the case of UMD). Tree-shaking on webpack should prevent unused encoders from being included in the final bundle.
Parameter | Type | Description |
---|---|---|
mimeType |
String |
The MIME type of the encoder to create. Supported values are 'audio/mpeg' (MP3) or 'audio/ogg' (Ogg Vorbis) |
wasm |
String | ArrayBuffer | Uint8Array | WebAssembly.Module |
A URL, base64 data URL, buffer, or compiled WebAssembly.Module representing the WASM binary for the specific mimeType . The WASM binaries are included in the package under wasm-media-encoders/wasm/(mp3|ogg).wasm . Non-data URLs are not supported in Node; use node-fetch if this is something you need. |
moduleCallback |
((module: WebAssembly.Module) => void) | undefined |
Optionally, a callback that will be called with the compiled WebAssembly module. You can cache this module client-side and pass it as the wasm parameter to avoid fetching and compiling it every time. |
WasmMediaEncoder
configure(options): void
Configures the encoder. This method can be called at any time to reset the state of the encoder, including after finalize()
.
The options object is a union of common properties and encoder-specific ones. All common options are required.
Common options:
Property | Type | Description |
---|---|---|
channels |
Number |
The number of channels to be encoded. Currently only 1 or 2 channels are supported. |
sampleRate |
Number |
Sample rate of data to be encoded, in hertz. |
Options for MIME type audio/mpeg
(MP3):
vbrQuality
and bitrate
are mutually exclusive.
Property | Type | Default | Description |
---|---|---|---|
vbrQuality |
Number | undefined |
4.0 |
Variable Bitrate (VBR) quality for the LAME encoder, from 0.0 (best quality) to 9.999 (worst quality). See here for details. |
bitrate |
Number | undefined |
Constant bitrate in kbit/s. Valid bitrates are 8, 16, 24, 32, 40, 48, 64, 80, 96, 112, 128, 160, 192, 224, 256, or 320. |
Options for MIME type audio/ogg
(Ogg Vorbis):
Property | Type | Default | Description |
---|---|---|---|
vbrQuality |
Number | undefined |
3.0 |
Variable Bitrate (VBR) quality for the Vorbis encoder, from -1.0 (worst quality) to 10.0 (best quality). See here for approximate bitrates. |
encode(samples): Uint8Array
Encodes PCM samples and returns a Uint8Array
. You may call this method repeatedly to add more samples (e.g. if streaming in PCM data). May return a Uint8Array
of length zero. The returned Uint8Array
is owned by the encoder and MUST be copied before any other encoder methods are called.
Parameter | Type | Description |
---|---|---|
samples |
Float32Array[] |
A channels -length array of Float32Array representing the PCM data to encode. Each sample must be in the range of -1.0 to 1.0
|
finalize(): Uint8Array
Flushes the encoder and returns the last few encoded samples. May return a Uint8Array
of length zero. The returned Uint8Array
is owned by the encoder and MUST be copied before any other encoder methods are called.
License
This project is licensed under the terms of the MIT license.