node-webcodecs

Native WebCodecs API implementation for Node.js, using FFmpeg for encoding and decoding.

Features

• W3C WebCodecs API compatible - Same API as the browser WebCodecs
• Non-blocking async encoding/decoding - Worker thread pool keeps the event loop responsive
• Hardware acceleration - VideoToolbox (macOS), NVENC (NVIDIA), QSV (Intel), VAAPI (Linux)
• Video codecs: H.264/AVC, H.265/HEVC, VP8, VP9, AV1
• Audio codecs: AAC, Opus, FLAC, MP3
• ImageDecoder - Decode JPEG, PNG, GIF, WebP, BMP images with ReadableStream support
• Native codec probing - isConfigSupported actually tests codec availability
• HDR support - BT.2020, PQ (HDR10), HLG color spaces
• Alpha channel - VP8/VP9 with transparency (alpha: 'keep')
• Scalability modes - Temporal layer SVC (L1T1, L1T2, L1T3)
• Latency modes - 'quality' vs 'realtime' encoding
• Bitrate modes - 'constant', 'variable', 'quantizer'
• High performance - Native C++ bindings with FFmpeg
• Backpressure support - encodeQueueSize, decodeQueueSize, and dequeue events
• TypeScript support - Full type definitions included

Requirements

• Node.js 18+
• No system dependencies on linux-x64, linux-arm64, and macOS arm64 — see below

The loader resolves a native binding in this order:

1. Dynamic prebuild — links your system FFmpeg (all codecs your FFmpeg has, including GPL ones like x264/x265). Requires FFmpeg runtime libraries whose major version matches the prebuild: FFmpeg 6.x on Linux (e.g. Ubuntu 24.04), current Homebrew FFmpeg on macOS.
2. Static prebuild — a statically-linked, LGPL-only FFmpeg shipped as a platform-specific @node-webcodecs/static-* optional dependency (~15 MB, only your platform is downloaded). Zero system dependencies: works in any Docker base image, Lambda, Fly, etc. H.264 encode uses openh264, AV1 encode uses SVT-AV1, AV1 decode uses dav1d. No GPL components, so software HEVC encode is unavailable (hardware HEVC encode still works where present).
3. Source build — cmake-js compiles against your FFmpeg dev headers. Requires cmake, pkg-config, a C++ compiler, and FFmpeg dev packages.

Set NODE_WEBCODECS_FORCE=dynamic|static|source to pin a specific variant (both at install time and at runtime), and call getNativeVariant() to see which one loaded.

Installing Dependencies

Only needed for the dynamic prebuild (preferred when present) or source builds — installs with none of this work via the static prebuild.

macOS (Homebrew):

brew install ffmpeg

# Ensure Homebrew is in your PATH (add to ~/.zshrc or ~/.bashrc)
export PATH="/opt/homebrew/bin:$PATH"

Ubuntu/Debian:

sudo apt-get install libavcodec-dev libavutil-dev libswscale-dev libswresample-dev

Windows (builds from source): Install FFmpeg and add to PATH, or use vcpkg. Ensure pkg-config and a C++ compiler are available.

Installation

npm install node-webcodecs

Quick Start

Video Encoding

const { VideoEncoder, VideoFrame } = require('node-webcodecs');

const encoder = new VideoEncoder({
  output: (chunk, metadata) => {
    console.log(`Encoded: ${chunk.byteLength} bytes`);
  },
  error: (err) => console.error(err),
});

encoder.configure({
  codec: 'avc1.42E01E',  // H.264 Baseline
  width: 640,
  height: 480,
  bitrate: 1_000_000,
});

// Create frame from RGBA buffer
const frame = new VideoFrame(rgbaBuffer, {
  format: 'RGBA',
  codedWidth: 640,
  codedHeight: 480,
  timestamp: 0,
});

encoder.encode(frame, { keyFrame: true });
frame.close();

await encoder.flush();
encoder.close();

Video Decoding

const { VideoDecoder, EncodedVideoChunk } = require('node-webcodecs');

const decoder = new VideoDecoder({
  output: (frame) => {
    console.log(`Decoded: ${frame.codedWidth}x${frame.codedHeight}`);
    frame.close();
  },
  error: (err) => console.error(err),
});

decoder.configure({
  codec: 'avc1.42E01E',
  codedWidth: 640,
  codedHeight: 480,
});

// Decode an encoded chunk
decoder.decode(encodedChunk);
await decoder.flush();
decoder.close();

Audio Encoding

const { AudioEncoder, AudioData } = require('node-webcodecs');

const encoder = new AudioEncoder({
  output: (chunk, metadata) => {
    console.log(`Encoded: ${chunk.byteLength} bytes`);
  },
  error: (err) => console.error(err),
});

encoder.configure({
  codec: 'mp4a.40.2',  // AAC-LC
  sampleRate: 48000,
  numberOfChannels: 2,
  bitrate: 128000,
});

const audio = new AudioData({
  format: 'f32',
  sampleRate: 48000,
  numberOfFrames: 1024,
  numberOfChannels: 2,
  timestamp: 0,
  data: floatSamples,
});

encoder.encode(audio);
audio.close();

await encoder.flush();
encoder.close();

Image Decoding

const { ImageDecoder } = require('node-webcodecs');
const fs = require('fs');

const imageData = fs.readFileSync('photo.jpg');

const decoder = new ImageDecoder({
  data: imageData,
  type: 'image/jpeg',
});

await decoder.completed;

console.log(`Image: ${decoder.tracks.selectedTrack.frameCount} frame(s)`);

const result = await decoder.decode({ frameIndex: 0 });
const frame = result.image;

console.log(`Decoded: ${frame.codedWidth}x${frame.codedHeight}`);
frame.close();
decoder.close();

Advanced Encoding Options

// HDR encoding with BT.2020 + PQ
encoder.configure({
  codec: 'hvc1',
  width: 3840,
  height: 2160,
  bitrate: 20_000_000,
  colorSpace: {
    primaries: 'bt2020',
    transfer: 'pq',        // HDR10
    matrix: 'bt2020-ncl',
    fullRange: false,
  },
});

// Low-latency realtime encoding
encoder.configure({
  codec: 'avc1.42E01E',
  width: 1280,
  height: 720,
  bitrate: 2_000_000,
  latencyMode: 'realtime',
  bitrateMode: 'constant',
});

// VP9 with alpha channel
encoder.configure({
  codec: 'vp09.00.10.08',
  width: 640,
  height: 480,
  bitrate: 1_000_000,
  alpha: 'keep',  // Preserve alpha channel
});

// Temporal layer SVC
encoder.configure({
  codec: 'vp09.00.10.08',
  width: 1280,
  height: 720,
  bitrate: 2_000_000,
  scalabilityMode: 'L1T2',  // 1 spatial, 2 temporal layers
});

Supported Codecs

Video Codecs

Codec String	Description	SW Encoder	HW Encoder
avc1.PPCCLL	H.264/AVC	libx264	VideoToolbox, NVENC, QSV
hvc1, hev1	H.265/HEVC	libx265	VideoToolbox, NVENC, QSV
vp8	VP8	libvpx	-
vp9, vp09.PP.LL.DD	VP9	libvpx-vp9	VAAPI, QSV
av01	AV1	libsvtav1	NVENC (RTX 40+), QSV

Hardware Acceleration

Hardware encoders are automatically selected when available. You can control this with the hardwareAcceleration option:

encoder.configure({
  codec: 'avc1.42E01E',
  width: 1920,
  height: 1080,
  bitrate: 5_000_000,
  hardwareAcceleration: 'prefer-hardware',  // 'no-preference' | 'prefer-hardware' | 'prefer-software'
});

Supported Hardware Accelerators

Platform	Accelerator	H.264	HEVC	VP9	AV1
macOS	VideoToolbox	Encode/Decode	Encode/Decode	-	-
Windows/Linux	NVIDIA NVENC	Encode	Encode	-	Encode (RTX 40+)
Windows/Linux	Intel QuickSync	Encode/Decode	Encode/Decode	Encode	Encode
Linux	VA-API	Encode/Decode	Encode/Decode	Encode	Encode

Async Worker Threads

By default, encoding and decoding operations run on a dedicated worker thread to avoid blocking the Node.js event loop. This keeps your application responsive during heavy video processing.

// Async mode (default) - event loop stays responsive
encoder.configure({
  codec: 'avc1.42E01E',
  width: 1920,
  height: 1080,
  bitrate: 5_000_000,
  useWorkerThread: true,  // default
});

// Sync mode - blocks event loop (legacy behavior)
encoder.configure({
  codec: 'avc1.42E01E',
  width: 1920,
  height: 1080,
  bitrate: 5_000_000,
  useWorkerThread: false,
});

Benchmark results show async mode allows 3100% more event loop iterations compared to sync mode, meaning your HTTP servers, timers, and I/O operations continue running smoothly during encoding.

Use with Mediabunny

Mediabunny reads and writes MP4/WebM files using the environment's WebCodecs. One import gives it this package's codecs in Node:

import 'node-webcodecs/mediabunny';  // WebCodecs globals + resize support
// or, without the Mediabunny-specific extras:
import 'node-webcodecs/register';    // just the WebCodecs globals

import { Input, ALL_FORMATS, FilePathSource, VideoSampleSink } from 'mediabunny';

const input = new Input({ formats: ALL_FORMATS, source: new FilePathSource('video.mp4') });
const track = await input.getPrimaryVideoTrack();
const sink = new VideoSampleSink(track);

for await (const sample of sink.samples()) {
  // full-speed, frame-accurate decoding — no browser required
  sample.close();
}

Measured against @mediabunny/server (NodeAV backend) on the same 1080p file: ~7x faster full-file decode, identical pixels, and 1.5x faster resize transcodes. node-webcodecs/mediabunny registers a VideoSample transformer covering plain resizing (fit: 'fill', or contain/cover with matching aspect ratio); rotation and cropping are not yet handled.

Performance

Decoding is multithreaded (FFmpeg auto-detects core count) and decoded frames are delivered zero-copy. Measured at 1080p over 150 frames on an Apple M4 Pro (v1.1.4, software codecs):

Operation	Throughput
H.264 decode	~1,800 fps
VP9 decode	~1,570 fps
VP9 encode	~49 fps
H.264 encode (VideoToolbox)	~220 fps

Relative to v1.0.0 this is 3–6× faster decoding and ~3× faster VP9 encoding.

Audio Codecs

Codec String	Description	Encoder	Decoder
mp4a.40.2	AAC-LC	aac	aac
opus	Opus	libopus	opus
flac	FLAC (lossless)	flac	flac
mp3	MP3	libmp3lame	mp3

API Reference

VideoEncoder

const encoder = new VideoEncoder(init: VideoEncoderInit);
encoder.configure(config: VideoEncoderConfig);
encoder.encode(frame: VideoFrame, options?: VideoEncoderEncodeOptions);
await encoder.flush();
encoder.close();
encoder.reset();

// Static method to check codec support
const support = await VideoEncoder.isConfigSupported(config);

VideoDecoder

const decoder = new VideoDecoder(init: VideoDecoderInit);
decoder.configure(config: VideoDecoderConfig);
decoder.decode(chunk: EncodedVideoChunk);
await decoder.flush();
decoder.close();
decoder.reset();

// Static method to check codec support
const support = await VideoDecoder.isConfigSupported(config);

AudioEncoder

const encoder = new AudioEncoder(init: AudioEncoderInit);
encoder.configure(config: AudioEncoderConfig);
encoder.encode(data: AudioData);
await encoder.flush();
encoder.close();
encoder.reset();

AudioDecoder

const decoder = new AudioDecoder(init: AudioDecoderInit);
decoder.configure(config: AudioDecoderConfig);
decoder.decode(chunk: EncodedAudioChunk);
await decoder.flush();
decoder.close();
decoder.reset();

ImageDecoder

const decoder = new ImageDecoder(init: ImageDecoderInit);
await decoder.completed;              // Promise that resolves when ready
decoder.type;                         // MIME type
decoder.tracks;                       // ImageTrackList with frame info
const result = await decoder.decode({ frameIndex: 0 });
decoder.close();

// Supported types: image/jpeg, image/png, image/gif, image/webp, image/bmp

VideoFrame

const frame = new VideoFrame(data: BufferSource, init: VideoFrameBufferInit);
frame.codedWidth;
frame.codedHeight;
frame.timestamp;
frame.duration;
frame.format;
frame.allocationSize(options?);
frame.copyTo(destination, options?);
frame.clone();
frame.close();

AudioData

const audio = new AudioData(init: AudioDataInit);
audio.sampleRate;
audio.numberOfFrames;
audio.numberOfChannels;
audio.format;
audio.timestamp;
audio.duration;
audio.allocationSize(options?);
audio.copyTo(destination, options?);
audio.clone();
audio.close();

Examples

See the examples/ directory for more usage examples:

• basic-video-encode.js - Simple video encoding
• basic-audio-encode.js - Simple audio encoding
• encode-decode-roundtrip.js - Full encode/decode cycle

Runtime Support

Runtime	Version	Status
Node.js	18+	Supported
Bun	1.0+	Supported

Bun Installation

bun add node-webcodecs

If the native binary doesn't compile automatically, you may need to trust the package:

bun pm trust node-webcodecs

Building from Source

git clone https://github.com/caseymanos/node-webcodecs.git
cd node-webcodecs
npm install
npm run build
npm test

License

MIT