canvas-record
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5.0.0 • Public • Published

canvas-record

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Record a video in the browser or directly on the File System from a canvas (2D/WebGL/WebGPU) as MP4, WebM, MKV, GIF, PNG/JPG Sequence using WebCodecs and Wasm when available.

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Installation

npm install canvas-record

Usage

import { Recorder, RecorderStatus, Encoders } from "canvas-record";
import createCanvasContext from "canvas-context";
import { AVC } from "media-codecs";

// Setup
const pixelRatio = devicePixelRatio;
const width = 512;
const height = 512;
const { context, canvas } = createCanvasContext("2d", {
  width: width * pixelRatio,
  height: height * pixelRatio,
  contextAttributes: { willReadFrequently: true },
});
Object.assign(canvas.style, { width: `${width}px`, height: `${height}px` });

const mainElement = document.querySelector("main");
mainElement.appendChild(canvas);

// Animation
let canvasRecorder;

function render() {
  const width = canvas.width;
  const height = canvas.height;

  const t = canvasRecorder.frame / canvasRecorder.frameTotal || Number.EPSILON;

  context.clearRect(0, 0, width, height);
  context.fillStyle = "red";
  context.fillRect(0, 0, t * width, height);
}

const tick = async () => {
  render();

  if (canvasRecorder.status !== RecorderStatus.Recording) return;
  await canvasRecorder.step();

  if (canvasRecorder.status !== RecorderStatus.Stopped) {
    requestAnimationFrame(() => tick());
  }
};

canvasRecorder = new Recorder(context, {
  name: "canvas-record-example",
  encoderOptions: {
    codec: AVC.getCodec({ profile: "Main", level: "5.2" }),
  },
});

// Start and encode frame 0
await canvasRecorder.start();

// Animate to encode the rest
tick(canvasRecorder);

API

Encoder comparison:

Encoder Extension Required Web API WASM Speed
WebCodecs mp4 / webm / mkv WebCodecs Fast
MP4Wasm mp4 WebCodecs ✅ (embed) Fast
H264MP4 mp4 ✅ (embed) Medium
FFmpeg mp4 / webm SharedArrayBuffer ✅ (need binary path) Slow
GIF gif WebWorkers (wip) Fast
Frame png / jpg File System Access Fast
MediaCapture mkv / webm MediaStream Realtime

Note:

  • WebCodecs encoderOptions allow different codecs to be used: VP8/VP9/AV1/HEVC. See media-codecs to get a codec string from human readable options and check which ones are supported in your browser with github.io/media-codecs.
  • WebCodecs 5-10x faster than H264MP4Encoder and 20x faster than FFmpeg (it needs to mux files after writing png to virtual FS)
  • FFmpeg (mp4 and webm) and WebCodecs (mp4) have a AVC maximum frame size of 9437184 pixels. That's fine until a bit more than 4K 16:9 @ 30fps. So if you need 4K Square or 8K exports, be patient with H264MP4Encoder (which probably also has the 4GB memory limit) or use Frame encoder and mux them manually with FFmpeg CLI (ffmpeg -framerate 30 -i "%05d.jpg" -b:v 60M -r 30 -profile:v baseline -pix_fmt yuv420p -movflags +faststart output.mp4)
  • MP4Wasm is embedded from mp4-wasm for ease of use (FFmpeg will require encoderOptions.corePath)

Roadmap:

  • [ ] add debug logging
  • [ ] use WebWorkers for gifenc

Modules

canvas-record

Re-export Recorder, RecorderStatus, all Encoders and utils.

Classes

Recorder
Encoder
FFmpegEncoder
FrameEncoder
GIFEncoder
H264MP4Encoder
MP4WasmEncoder
MediaCaptureEncoder
WebCodecsEncoder

Constants

isWebCodecsSupported : boolean

Check for WebCodecs support on the current platform.

Functions

estimateBitRate(width, height, frameRate, motionRank, bitrateMode)number

Estimate the bit rate of a video rounded to nearest megabit. Based on "H.264 for the rest of us" by Kush Amerasinghe.

Typedefs

onStatusChangeCb : function

A callback to notify on the status change. To compare with RecorderStatus enum values.

RecorderOptions : object

Options for recording. All optional.

RecorderStartOptions : object

Options for recording initialisation. All optional.

EncoderExtensions : "mp4" | "webm" | "png" | "jpg" | "gif" | "mkv"
EncoderTarget : "in-browser" | "file-system"
FFmpegEncoderOptions : object
FFmpegEncoderEncoderOptions : module:@ffmpeg/ffmpeg/dist/esm/types.js~FFMessageLoadConfig
GIFEncoderOptions : object
GIFEncoderQuantizeOptions : object
GIFEncoderEncoderOptions : object
H264MP4EncoderOptions : object
H264MP4EncoderEncoderOptions : module:h264-mp4-encoder~H264MP4Encoder
MP4WasmEncoderOptions : object
MP4WasmEncoderEncoderOptions : VideoEncoderConfig
MediaCaptureEncoderOptions : object
MediaCaptureEncoderEncoderOptions : MediaRecorderOptions
WebCodecsEncoderOptions : object
WebCodecsEncoderEncoderOptions : VideoEncoderConfig
WebCodecsMuxerOptions : MuxerOptions

canvas-record

Re-export Recorder, RecorderStatus, all Encoders and utils.

Recorder

Kind: global class

new Recorder(context, [options])

Create a Recorder instance

Param Type Default
context RenderingContext
[options] RecorderOptions {}

recorder.defaultOptions : RecorderOptions

Sensible defaults for recording so that the recorder "just works".

Kind: instance property of Recorder

recorder.mimeTypes : object

A mapping of extension to their mime types

Kind: instance property of Recorder

recorder.start([startOptions])

Start the recording by initializing and optionally calling the initial step.

Kind: instance method of Recorder

Param Type Default
[startOptions] RecorderStartOptions {}

recorder.step()

Encode a frame and increment the time and the playhead. Calls await canvasRecorder.stop() when duration is reached.

Kind: instance method of Recorder

recorder.stop() ⇒ ArrayBuffer | Uint8Array | Array.<Blob> | undefined

Stop the recording and return the recorded buffer. If options.download is set, automatically start downloading the resulting file. Is called when duration is reached or manually.

Kind: instance method of Recorder

recorder.dispose()

Clean up the recorder and encoder

Kind: instance method of Recorder

Encoder

Kind: global class Properties

Name Type
target EncoderTarget
extension EncoderExtensions
[encoderOptions] object
[muxerOptions] object

new Encoder(options)

Base Encoder class. All Encoders extend it and its method are called by the Recorder.

Param Type
options object

encoder.supportedExtensions : Array.<Extensions>

The extension the encoder supports

Kind: instance property of Encoder

encoder.supportedTargets : Array.<EncoderTarget>

The target to download the file to.

Kind: instance property of Encoder

encoder.init(options)

Setup the encoder: load binary, instantiate muxers, setup file system target...

Kind: instance method of Encoder

Param Type
options object

encoder.encode(frame, [frameNumber])

Encode a single frame. The frameNumber is usually used for GOP (Group Of Pictures).

Kind: instance method of Encoder

Param Type
frame number
[frameNumber] number

encoder.stop() ⇒ ArrayBuffer | Uint8Array | Array.<Blob> | undefined

Stop the encoding process and cleanup the temporary data.

Kind: instance method of Encoder

encoder.dispose()

Clean up the encoder

Kind: instance method of Encoder

FFmpegEncoder

Kind: global class

new FFmpegEncoder([options])

Param Type
[options] FFmpegEncoderOptions

FrameEncoder

Kind: global class

GIFEncoder

Kind: global class

new GIFEncoder([options])

Param Type
[options] GIFEncoderOptions

H264MP4Encoder

Kind: global class

new H264MP4Encoder([options])

Param Type
[options] H264MP4EncoderOptions

MP4WasmEncoder

Kind: global class

new MP4WasmEncoder([options])

Param Type
[options] MP4WasmEncoderOptions

MediaCaptureEncoder

Kind: global class

new MediaCaptureEncoder([options])

Param Type
[options] MediaCaptureEncoderOptions

WebCodecsEncoder

Kind: global class

new WebCodecsEncoder([options])

Param Type
[options] WebCodecsEncoderOptions

RecorderStatus : enum

Enum for recorder status

Kind: global enum Read only: true Example

// Check recorder status before continuing
if (canvasRecorder.status !== RecorderStatus.Stopped) {
  rAFId = requestAnimationFrame(() => tick());
}

isWebCodecsSupported : boolean

Check for WebCodecs support on the current platform.

Kind: global constant

estimateBitRate(width, height, frameRate, motionRank, bitrateMode) ⇒ number

Estimate the bit rate of a video rounded to nearest megabit. Based on "H.264 for the rest of us" by Kush Amerasinghe.

Kind: global function Returns: number - A bitrate value in bits per second

Param Type Default Description
width number
height number
frameRate number 30
motionRank number 4 A factor of 1, 2 or 4
bitrateMode "variable" | "constant" variable

Example

// Full HD (1080p)
const bitRate = estimateBitRate(1920, 1080, 30, "variable");
const bitRateMbps = bitRate * 1_000_000; // => 13 Mbps

onStatusChangeCb : function

A callback to notify on the status change. To compare with RecorderStatus enum values.

Kind: global typedef

Param Type Description
RecorderStatus number the status

RecorderOptions : object

Options for recording. All optional.

Kind: global typedef Properties

Name Type Default Description
[name] string "&quot;&quot;" A name for the recorder, used as prefix for the default file name.
[duration] number 10 The recording duration in seconds. If set to Infinity, await canvasRecorder.stop() needs to be called manually.
[frameRate] number 30 The frame rate in frame per seconds. Use await canvasRecorder.step(); to go to the next frame.
[download] boolean true Automatically download the recording when duration is reached or when await canvasRecorder.stop() is manually called.
[extension] string "&quot;mp4&quot;" Default file extension: infers which Encoder is selected.
[target] string "&quot;in-browser&quot;" Default writing target: in-browser or file-system when available.
[encoder] object A specific encoder. Default encoder based on options.extension: GIF > WebCodecs > H264MP4.
[encoderOptions] object See src/encoders or individual packages for a list of options.
[muxerOptions] object See "mp4-muxer" and "webm-muxer" for a list of options.
[onStatusChange] onStatusChangeCb

RecorderStartOptions : object

Options for recording initialisation. All optional.

Kind: global typedef Properties

Name Type Description
[filename] string Overwrite the file name completely.
[initOnly] boolean Only initialised the recorder and don't call the first await recorder.step().

EncoderExtensions : "mp4" | "webm" | "png" | "jpg" | "gif" | "mkv"

Kind: global typedef

EncoderTarget : "in-browser" | "file-system"

Kind: global typedef

FFmpegEncoderOptions : object

Kind: global typedef Properties

Name Type Default
[encoderOptions] FFmpegEncoderEncoderOptions {}

FFmpegEncoderEncoderOptions : module:@ffmpeg/ffmpeg/dist/esm/types.js~FFMessageLoadConfig

Kind: global typedef See: FFmpeg#load

GIFEncoderOptions : object

Kind: global typedef Properties

Name Type Default
[maxColors] number 256
[quantizeOptions] GIFEncoderQuantizeOptions
[encoderOptions] GIFEncoderEncoderOptions {}

GIFEncoderQuantizeOptions : object

Kind: global typedef See: QuantizeOptions Properties

Name Type Default
[format] "rgb565" | "rgb444" | "rgba4444" "rgb565"
[oneBitAlpha] boolean | number false
[clearAlpha] boolean true
[clearAlphaThreshold] number 0
[clearAlphaColor] number 0x00

GIFEncoderEncoderOptions : object

Kind: global typedef See: WriteFrameOpts Properties

Name Type Default
[palette] Array.<Array.<number>>
[first] boolean false
[transparent] boolean 0
[transparentIndex] number 0
[delay] number 0
[repeat] number 0
[dispose] number -1

H264MP4EncoderOptions : object

Kind: global typedef Properties

Name Type Default
[debug] boolean
[encoderOptions] H264MP4EncoderEncoderOptions {}

H264MP4EncoderEncoderOptions : module:h264-mp4-encoder~H264MP4Encoder

Kind: global typedef See: h264-mp4-encoder#api

MP4WasmEncoderOptions : object

Kind: global typedef Properties

Name Type Default
[groupOfPictures] number 20
[flushFrequency] number 10
[encoderOptions] MP4WasmEncoderEncoderOptions {}

MP4WasmEncoderEncoderOptions : VideoEncoderConfig

Kind: global typedef See: VideoEncoder.configure

MediaCaptureEncoderOptions : object

Kind: global typedef Properties

Name Type Default
[flushFrequency] number 10
[encoderOptions] MediaCaptureEncoderEncoderOptions {}

MediaCaptureEncoderEncoderOptions : MediaRecorderOptions

Kind: global typedef See: MediaRecorder#options

WebCodecsEncoderOptions : object

Kind: global typedef Properties

Name Type Default
[groupOfPictures] number 20
[flushFrequency] number 10
[encoderOptions] WebCodecsEncoderEncoderOptions {}

WebCodecsEncoderEncoderOptions : VideoEncoderConfig

Kind: global typedef See: VideoEncoder.configure

WebCodecsMuxerOptions : MuxerOptions

Kind: global typedef See

License

All MIT:

MIT. See license file.

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