Kagami/ffmpeg.js

• {type: "run", ...opts} - Start new job with provided options.

const worker = new Worker("ffmpeg-worker-webm.js");
worker.onmessage = function(e) {
  const msg = e.data;
  switch (msg.type) {
  case "ready":
    worker.postMessage({type: "run", arguments: ["-version"]});
    break;
  case "stdout":
    console.log(msg.data);
    break;
  case "stderr":
    console.log(msg.data);
    break;
  case "done":
    console.log(msg.data);
    break;
  }
};

You can use worker_threads module in case of Node.

Files

Empscripten supports several types of file systems. ffmpeg.js uses MEMFS to store the input/output files in FFmpeg's working directory. You need to pass Array of Object to MEMFS option with the following keys:

• name (String) - File name, can't contain slashes.
• data (ArrayBuffer/ArrayBufferView/Array) - File data.

const ffmpeg = require("ffmpeg.js");
const fs = require("fs");
const testData = new Uint8Array(fs.readFileSync("test.webm"));
// Encode test video to VP8.
const result = ffmpeg({
  MEMFS: [{name: "test.webm", data: testData}],
  arguments: ["-i", "test.webm", "-c:v", "libvpx", "-an", "out.webm"],
});
// Write out.webm to disk.
const out = result.MEMFS[0];
fs.writeFileSync(out.name, Buffer(out.data));

You can also mount other FS by passing Array of Object to mounts option with the following keys:

• type (String) - Name of the file system.
• opts (Object) - Underlying file system options.
• mountpoint (String) - Mount path, must start with a slash, must not contain other slashes and also the following paths are blacklisted: /tmp, /home, /dev, /work. Mount directory will be created automatically before mount.

const ffmpeg = require("ffmpeg.js");
ffmpeg({
  // Mount /data inside application to the current directory.
  mounts: [{type: "NODEFS", opts: {root: "."}, mountpoint: "/data"}],
  arguments: ["-i", "/data/test.webm", "-c:v", "libvpx", "-an", "-y", "/data/out.webm"],
});
// out.webm was written to the current directory.

Build instructions

It's recommended to use Docker to build ffmpeg.js.

1. Clone ffmpeg.js repository with submodules:

    git clone https://github.com/Kagami/ffmpeg.js.git --recurse-submodules
    

2. Modify Makefile and/or patches if you wish to make a custom build.

3. Build everything:

    docker run --rm -it -v /path/to/ffmpeg.js:/mnt -w /opt kagamihi/ffmpeg.js
    # cp -a /mnt/{.git,build,Makefile} . && source /root/emsdk/emsdk_env.sh && make && cp ffmpeg*.js /mnt
    

That's it. ffmpeg.js modules should appear in your repository clone.

Build without Docker

Ubuntu example:

sudo apt-get update
sudo apt-get install -y git python build-essential automake libtool pkg-config
cd ~
git clone https://github.com/emscripten-core/emsdk.git && cd emsdk
./emsdk install latest
./emsdk activate latest
source emsdk_env.sh
cd ~
git clone https://github.com/Kagami/ffmpeg.js.git --recurse-submodules && cd ffmpeg.js
make

Credits

Thanks to videoconverter.js for inspiration. And of course to all great projects which made this library possible: FFmpeg, Emscripten, asm.js, node.js and many others.

License

Own library code licensed under LGPL 2.1 or later.

WebM build

This build uses LGPL version of FFmpeg and thus available under LGPL 2.1 or later. See here for more details and FFmpeg's license information.

Included libraries:

• libopus licensed under BSD.
• libvpx licensed under BSD.

MP4 build

This build uses GPL version of FFmpeg and thus available under GPL 2.0. It also includes patent encumbered H.264, AAC and MP3 encoders. Make sure to contact lawyer before using it in your country.

Included libraries:

• x264 licensed under GPL.
• LAME licensed under LGPL.