ffmpeg.wasm

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ffmpeg.wasm is a pure Webassembly / Javascript port of FFmpeg. It enables video & audio record, convert and stream right inside browsers.

AVI to MP4 Demo

Try it: https://ffmpegwasm.netlify.app

Check next steps of ffmpeg.wasm HERE

Installation

Node

``
$ npm install @ffmpeg/ffmpeg @ffmpeg/core
`

> As we are using experimental features, you need to add flags to run in Node.js

`
$ node --experimental-wasm-threads transcode.js
`

Browser

Or, using a script tag in the browser (only works in some browsers, see list below):

> SharedArrayBuffer is only available to pages that are cross-origin isolated. So you need to host your own server with Cross-Origin-Embedder-Policy: require-corp and Cross-Origin-Opener-Policy: same-origin headers to use ffmpeg.wasm.

`html


`

> Only browsers with SharedArrayBuffer support can use ffmpeg.wasm, you can check HERE for the complete list.

Usage

ffmpeg.wasm provides simple to use APIs, to transcode a video you only need few lines of code:

`javascript
import { writeFile } from 'fs/promises';
import { createFFmpeg, fetchFile } from '@ffmpeg/ffmpeg';

const ffmpeg = createFFmpeg({ log: true });

(async () => {
await ffmpeg.load();
ffmpeg.FS('writeFile', 'test.avi', await fetchFile('./test.avi'));
await ffmpeg.run('-i', 'test.avi', 'test.mp4');
await fs.promises.writeFile('./test.mp4', ffmpeg.FS('readFile', 'test.mp4'));
process.exit(0);
})();
`

$3

For each version of ffmpeg.wasm, there is a default version of @ffmpeg/core (you can find it in devDependencies section of package.json), but sometimes you may need to use newer version of @ffmpeg/core to use the latest/experimental features.

Node

Just install the specific version you need:

`bash
$ npm install @ffmpeg/core@latest
`

Or use your own version with customized path

`javascript
const ffmpeg = createFFmpeg({
corePath: '../../../src/ffmpeg-core.js',
});
`

Browser

`javascript
const ffmpeg = createFFmpeg({
corePath: 'static/js/ffmpeg-core.js',
});
`

Keep in mind that for compatibility with webworkers and nodejs this will default to a local path, so it will attempt to look for 'static/js/ffmpeg.core.js' locally, often resulting in a local resource error. If you wish to use a core version hosted on your own domain, you might reference it relatively like this:

`javascript
const ffmpeg = createFFmpeg({
corePath: new URL('static/js/ffmpeg-core.js', document.location).href,
});
`

For the list available versions and their changelog, please check: https://github.com/ffmpegwasm/ffmpeg.wasm-core/releases

$3

`javascript
const ffmpeg = createFFmpeg({
mainName: 'main',
corePath: 'https://unpkg.com/@ffmpeg/core-st@0.11.1/dist/ffmpeg-core.js',
});
`

Multi-threading

Multi-threading need to be configured per external libraries, only following libraries supports it now:

$3

Run it multi-threading mode by default, no need to pass any arguments.

$3

Need to pass -row-mt 1, but can only use one thread to help, can speed up around 30%

Documentation

- API
- Supported External Libraries

FAQ

$3

There are two components inside ffmpeg.wasm:

- @ffmpeg/ffmpeg (https://github.com/ffmpegwasm/ffmpeg.wasm)
- @ffmpeg/core (https://github.com/ffmpegwasm/ffmpeg.wasm-core)

@ffmpeg/core contains WebAssembly code which is transpiled from original FFmpeg C code with minor modifications, but overall it still following the same licenses as FFmpeg and its external libraries (as each external libraries might have its own license).

@ffmpeg/ffmpeg contains kind of a wrapper to handle the complexity of loading core and calling low-level APIs. It is a small code base and under MIT license.

$3

Yes, but only for Firefox 79+ with proper header in both client and server, visit https://ffmpegwasm.netlify.app to try whether your Firefox works.

![](https://user-images.githubusercontent.com/5723124/98955802-4cb20c80-253a-11eb-8f16-ce0298720a2a.png)

For more details: https://github.com/ffmpegwasm/ffmpeg.wasm/issues/106

$3

2 GB, which is a hard limit in WebAssembly. Might become 4 GB in the future.

$3

In fact, it is ffmpeg.wasm-core most people would like to build.

To build on your own, you can check build.sh inside https://github.com/ffmpegwasm/ffmpeg.wasm-core repository.

Also you can check this series of posts to learn more fundamental concepts:

- https://jeromewu.github.io/build-ffmpeg-webassembly-version-part-1-preparation/
- https://jeromewu.github.io/build-ffmpeg-webassembly-version-part-2-compile-with-emscripten/
- https://jeromewu.github.io/build-ffmpeg-webassembly-version-part-3-v0.1/
- https://jeromewu.github.io/build-ffmpeg-webassembly-version-part-4-v0.2/

$3

When calling ffmpeg.load(), by default it looks for http://localhost:3000/node_modules/@ffmpeg/core/dist/ to download essential files (ffmpeg-core.js, ffmpeg-core.wasm, ffmpeg-core.worker.js). It is necessary to make sure you have those files served there.

If you have those files serving in other location, you can rewrite the default behavior when calling createFFmpeg():

`javascript
const { createFFmpeg } = FFmpeg;
const ffmpeg = createFFmpeg({
corePath: "http://localhost:3000/public/ffmpeg-core.js",
// Use public address if you don't want to host your own.
// corePath: 'https://unpkg.com/@ffmpeg/core@0.10.0/dist/ffmpeg-core.js'
log: true,
});
``