Reactive Videos are videos created using HTML and React components. This allows you to leverage the almost limitless possibilities of the web browser to render dynamic content into a video file.

How does it work?

Reactive Video fires up one or more Puppeteer/Chromium tabs to render the React component hierarchy and rapidly capture screenshots for each frame when they are done rendering. It starts a HTTP server on localhost serving files (videos, images etc) needed to the Puppeteer client (protected by a token.)

Features

• Edit videos with code! 🤓
• Full power of the web
• Parallel rendering with multiple Chromium browser instances 🔥 Super fast (compared to editly)
• Supports all video formats/codecs that FFmpeg supports
• Headless mode (runs in the cloud)
• Output to any dimensions and aspect ratio, e.g. Instagram post (1:1), Instagram story (9:16), YouTube (16:9), or any other dimensions you like.
• Live preview for easy development
• Open source

Installation

First install and setup ffmpeg/ffprobe.

Then we can install the Reactive Video builder globally as a command line tool:

npm i -g @reactive-video/builder

Usage

Now create a file MyVideo.js with the content:

import React from 'react';
import { Image, Segment, Video, useVideo } from 'reactive-video';

export default () => {
  const { currentFrame, currentTime, durationFrames, durationTime } = useVideo();

  return (
    <>
      {/* This segment lasts for 30 frames. Print out the current frame number */}
      <Segment duration={30}>
        <div
          style={{ width: '100%', height: '100%', backgroundColor: `hsl(${(currentFrame * 10) % 360}deg 78% 37%)`, color: 'white', display: 'flex', alignItems: 'center', justifyContent: 'center', flexDirection: 'column', fontSize: 100 }}
        >
          Current frame {currentFrame}
        </div>
      </Segment>

      {/* This segment starts from 60 frames. Shows an image with a Ken Burns zoom effect */}
      <Segment
        start={30}
        duration={30}
        render={(segment) => (
          <Image src="https://static.mifi.no/losslesscut/47320816_571610306620180_5860442193520120371_n.jpg" style={{ width: '100%', transform: `scale(${1 + (segment.currentFrame / segment.durationFrames) * 0.1})` }} />
        )}
      />

      {/* This segment starts from 60 frames. Starts 100 frames into the source video (seek to) */}
      <Segment start={60}>
        <Segment start={-100}>
          <Video src="https://static.mifi.no/Zv5RvLhCz4M-small.mp4" style={{ width: '100%' }} />
        </Segment>
      </Segment>
    </>
  );
};

Download Chrome

You need to have installed Chrome/Chromium. Each version of Puppeteer is paired with a specific version of Chrome for Testing. Currently Chrome buildId 131.0.6778.85 is supported/tested. You can download the correct Chrome build to the directory browser (in the current directory):

npx @puppeteer/browsers install [email protected] --path /absolute/path/to/browser/dir

Linux ARM64

Chrome for Testing doesn't provide builds for Linux ARM64. However Playwright has Chromium builds for Linux ARM64, which can be used with puppeteer-core.

Steps to download Chromium:

1. Find the version of puppeteer-core used by reactive-video.
2. Find the Chrome for Testing version that our puppeteer-core version uses here (see also: https://github.com/puppeteer/puppeteer/blob/ddbb43cd09ccf8c4b3087960f8d2b20a385a8ec8/packages/puppeteer-core/src/revisions.ts).

• Find the Playwright revision field of chromium based on browserVersion (Chrome) by going back in git history in browsers.json.
• Then put the revision into the URL to download: wget https://playwright.azureedge.net/builds/chromium/$REVISION/chromium-linux-arm64.zip

Shell

Then run the CLI:

reactive-video --browser-exe-path /path/to/chrome --duration-frames 90 MyVideo.js

Duration can also be specified in seconds. See reactive-video --help

Live preview

Or to start a live preview:

reactive-video --browser-exe-path /path/to/chrome --duration-frames 90 MyVideo.js --preview
# or for HTML5 video:
reactive-video --browser-exe-path /path/to/chrome --duration-frames 90 MyVideo.js --preview-html

Programmatic API

Or you can use the programmatic Node API. Create a new Node.js project, then add @reactive-video/builder (not that reactive-video does not currently strictly follow semver):

mkdir awesome-reactive-video
cd awesome-reactive-video
npm init
npm i --save @reactive-video/builder

Create index.js:

import Editor from '@reactive-video/builder';
import { computeExecutablePath } from '@puppeteer/browsers';

// remember to download it first
const browserExePath = computeExecutablePath({ cacheDir: './browser', browser: 'chrome', buildId: '131.0.6778.85' });

const editor = Editor({
  ffmpegPath: 'ffmpeg',
  ffprobePath: 'ffprobe',
  browserExePath,
  devMode: true,
});

const width = 1280;
const height = 720;
const fps = 25;
const durationFrames = 90;
const reactVideo = 'MyVideo.js';
const userData = { some: 'value' };

// Build the video
await editor.edit({
  reactVideo,
  width,
  height,
  durationFrames,
  userData,

  output: 'my-video.mov',
  concurrency: 3,
  // headless: false,
  // extraPuppeteerArgs: ['--no-sandbox', '--disable-setuid-sandbox']

  // Optionally set rawOutput to false if you want to encode output to h264 (if not it will create MJPEG)
  // rawOutput: false,
});

// Or start a live preview:
await editor.preview({
  reactVideo,
  width,
  height,
  fps,
  durationFrames,
  userData,
});

Node API

Reactive Video has two parts:

• @reactive-video/builder: CLI and Node.js video builder API
• reactive-video: Code that runs in the React world. This package can also be installed in a separate frontend where you want to reuse Reactive Video code to render a video.

Data can be passed from Node.js to React via userData, which will become available in the useVideo hook.

Editor.edit / Editor.preview

import Editor from '@reactive-video/builder';

const { edit, preview } = Editor({ ffmpegPath, ffprobePath });

See editor.js edit and preview for options.

Editor.readVideoMetadata

Useful to read an input video's parameters and use it for your video, for instance if you want to render something on top of an existing video. Returns durationTime. If countFrames is true, returns also durationFrames, which is more accurate, but slower. Example:

import { pathToFileURL } from 'url';

const inputVideoPath = '/path/to/input-video.mp4';

const { edit, readVideoMetadata } = Editor();
const { width, height, fps, durationTime, durationFrames } = await readVideoMetadata({ path: inputVideoPath, countFrames: true });

await edit({
  reactVideo: 'MyVideo.js',
  width,
  height,
  fps,
  durationFrames,
  userData: { videoUri: pathToFileURL(inputVideoPath) },
  // videoUri becomes file:///path/to/input-video.mp4
});

Then in MyVideo.js:

export default () => {
  const { userData: { videoUri } } = useVideo();

  return <Video src={videoUri} />;
}

React API

impprt {
  Video,
  IFrame,
  Image,
  Segment,
  useVideo,
  useAsyncRenderer,
} from 'reactive-video'

<Video> component

Renders video frames synced to time

• src - See src below.
• htmlSrc - Override Video component src by specifying a different URL to be used when rendering the video code in e.g. a separate React frontend.
• scaleToWidth / scaleToHeight - Will cause ffmpeg to scale down the video before sending it to the page. Can give a great speed increase if scaling down a large source video.

For final rendering and preview, Reactive Video uses ffmpeg to stream individual frams to an <img> tag. Efficiently reuses the ffmpeg instance for sequential rendering. Supports virtually all formats that ffmpeg can seek in, even over HTTP (e.g. AWS S3)

Can also use HTML5 <video> for preview. Much faster seeking, but only supports certain codecs. Enabled with the --preview-html CLI flag.

<Image>

Works the same as HTML <image>. Waits for data to load.

• src - See src below.

<IFrame>

Works the same as HTML <iframe>. Waits for data to load.

• src - See src below.

src attribute

src must be a full, absolute file:// or http(s):// URI (e.g. file:///Users/me/video.webm or https://example.com/image.jpeg). Note the three slashes for local files! Tip: In Node.js you can use url.pathToFileURL to convert local (also relative) paths to file:// URIs. See example above.

useVideo

A hook that can be used to get the current video state.

const {
  // Global video properties
  fps,
  width,
  height,

  // Video (or Segment-relative) current frame:
  currentFrame,
  // Video (or Segment-relative) time:
  currentTime,
  // Video (or Segment) duration in frames:
  durationFrames,
  // Video (or Segment) duration in seconds:
  durationTime,

  // Value between 0 to 1 for the currentFrame's progress within the video (or Segment)
  // Useful for animating things inside segments.
  progress,

  // Global, never altered:
  video: {
    currentFrame,
    currentTime,
    durationFrames,
    durationTime,
  },

  // User JSON object passed from CLI (`--user-data`) or Node.js `userData` option
  userData,
} = useVideo();

useAsyncRenderer

A useEffect-like hook returning an async function that can be used to delay the frame capture operation due to an asynchronous task that needs to finish before drawing. Can also return an Array [async () => {}, cleanup: () => {}] if cleanup is needed. (will returned from useEffect). The first element of the array is the async function and the second element is the cleanup function.

const MyVideoOrComponent = () => {
  // ...

  useAsyncRenderer(async () => {
    setState(await api.loadSomeData(someParam));
  }, [someParam]);

  // or if you need to cleanup
  useAsyncRenderer(() => {
    let aborted = false;
    return [
      async () => {
        setState(await api.loadSomeData(someParam));
      },
      () => {
        aborted = true;
      }
    ];
  }, [someParam]);

  // ...
};

<Segment>

A Segment will, for a specific timespan specified by start and duration (specified in frames), render one of either:

1. Its provided children:

<Segment><MyComponent /></Segment>

2. or a render prop:

<Segment render={(props) => <MyComponent />} />

Segment props

• start - First frame that contents should be shown from (default: 0)
• duration - Number of frames that contents should be visible for (default: video durationFrames - start).
• override - Whether to override variables in the useVideo hook, see below (default: true)
• cut = Whether to cut off this component's children from rendering before start and after duration (default: true)

Segments will override the following variables in the useVideo hook for its children (unless override = false):

• currentFrame
• currentTime
• durationFrames
• durationTime

Theses variables will instead be relative to the start/duration of the Segment. If the render prop is used, the render function's provided props argument will also contain the same relative variables.

Importing resources

Resources are fetched from the local filesystem automatically during edit and preview with file:// or remotely using http(s)://. You can also import resources from your React components using ES6 import. This can be used to import css, images, and even videos, but it is recommended to not import large videos like this, as they will be copied to the dist directory during the compile.

// MyVideo.js
import React from 'react';
import { Image } from 'reactive-video';

import image from './image.jpeg';

export default () => (
  <Image src={image} style={{ width: 100 }} />
);

Reusing code in a different React app

npx create-react-app my-app
cd my-app
npm i --save reactive-video

Then you can import your Reactive Video code (e.g. MyVideo.js and dependencies) from a shared directory using your method of choice:

• npm/yarn workspaces (you may have to transpile the React code)
• git submodules
• ...

See example App.js:

import { VideoContextProvider } from 'reactive-video';

import MyVideo from 'path/to/MyVideo.js';

const App = () => {
  // You need to provide these parameters:
  const durationFrames = 1234;
  const width = 800;
  const height = 600;
  const fps = 30;

  const [currentFrame, setCurrentFrame] = useState();

  const canvasStyle = {
    width,
    height,
    overflow: 'hidden',
    position: 'relative',
    border: '3px solid black',
  };

  const userData = useMemo(() => {
    some: 'data',
  }, []);

  return (
    <div style={canvasStyle}>
      <VideoContextProvider
        currentFrame={currentFrame}
        durationFrames={durationFrames}
        width={width}
        height={height}
        fps={fps}
        userData={userData}
      >
        <MyVideo />
      </VideoContextProvider>
    </div>
  );
};

See also previewEntry.js

Options

rawOutput - true means saving the raw MJPEG/MPNG stream, while false will encode to h264

Lossless processing

If you want lossless processing, use these options. Note: very slow and yields large files:

ffmpegStreamFormat: 'raw'
// or ffmpegStreamFormat 'png'
puppeteerCaptureFormat: 'png',
rawOutput: true,

Examples

See examples

Your video here?

Submit a PR if you want to share your Reactive Video here.

TODO

• Improve docs
• Audio
• multiple FFmpegVideos from the same source file (videoServer.js) not supported
• FFmpegVideo fallback to previous frame if missing frame? (like HTML5Video) or make HTML5Video also work like FFmpegVideo
• puppeteer intercept request instead of starting local express server (if possible and fast to send big binary data). Will not work for preview.
• make it easier to animate (mount/unmount?) provide a react component that clamps animations? something like <Segment start={} duration={} easing="easeIn" />
• staggering animations (function helper or Stagger component)
• easing example code
• allow speed up/down <segment speed={1.3} />
• custom video component example
• preview currentFrame flooding browser history https://stackoverflow.com/questions/26793130/history-replacestate-still-adds-entries-to-the-browsing-history
• videoServer need to kill ffmpeg when finished with file? or use -t
• live video mode
• maybe not currently properly supporting different framerates. FFmpegVideo -vf fps in videoServer.js?
• use esbuild instead of webpack? https://esbuild.github.io/api/ so we can support typescript
  • or maybe remove bundler and allow people to bundle their own code for the reactive video

Ideas

• subtitle rendering (programmatically create Segments)
• easy merge videos recipe/helper
• webgl
• react three js
• create demo video, YouTube video
• editly features
• Recreate editly's video in reactive-video

Troubleshooting

• React webpage failed to initialize
  • Try to run with headless false and check puppeteer developer tools

Normalize rendering across operating systems

Because MacOS use sub-pixel rendering, fonts will look different. To work around this, use this in your CSS:

* {
  -webkit-font-smoothing: antialiased;
}

Puppeteer on Windows sometimes seems to use a different line-height, so it's recommended to fix it:

body {
  line-height: 1.2;
}

See also https://meyerweb.com/eric/tools/css/reset/

Useful commands for debugging videos

Compare hash of video content of two videos

ffmpeg -loglevel error -i vid1.mp4 -map 0:v -f md5 - && ffmpeg -loglevel error -i vid2.mp4 -map 0:v -f md5 -

Generate a visual diff

ffmpeg -i vid1.mp4 -i vid2.mp4 -filter_complex blend=all_mode=difference -c:v libx264 -crf 18 -c:a copy -y diff.mp4

Donate 🙈

This project is maintained by me alone. The project will always remain free and open source, but if it's useful for you, consider supporting me. :) It will give me extra motivation to improve it. Or even better donate to ffmpeg because they are doing the world a big favor 🙏

Release

Developer notes

See also

• editly - Declarative video API I also created earlier
• remotion - Great inspiration

Made with ❤️ in 🇳🇴

More apps by mifi.no

Follow me on GitHub, YouTube, IG, Twitter for more awesome content!