# 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.github.io](https://ffmpegwasm.github.io#demo)
## Installation
```
$ npm install @ffmpeg/ffmpeg @ffmpeg/core
```
> As we are using the latest experimental features, you need to add few flags to run in Node.js
```
$ node --experimental-wasm-threads --experimental-wasm-bulk-memory transcode.js
```
Or, using a script tag in the browser (only works in Chrome):
```html
```
> Only browsers with SharedArrayBuffer support can use ffmpeg.wasm, you can check [HERE](https://caniuse.com/sharedarraybuffer) for the complete list.
## Usage
ffmpeg.wasm provides simple to use APIs, to transcode a video you only need few lines of code:
```javascript
const fs = require('fs');
const { createFFmpeg, fetchFile } = require('@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);
})();
```
## Multi-threading
Multi-threading need to be configured per external libraries, only following libraries supports it now:
### x264
Run it multi-threading mode by default, no need to pass any arguments.
### libvpx / webm
Need to pass `-row-mt 1`, but can only use one thread to help, can speed up around 30%
## Documentation
- [API](https://github.com/ffmpegwasm/ffmpeg.wasm/blob/master/docs/api.md)
- [Supported External Libraries](https://github.com/ffmpegwasm/ffmpeg.wasm-core#configuration)