Files
hyperframes/packages/engine
Varo b390b71bde fix(engine): keep BeginFrame time monotonic across frame rates (#3011)
Fixes #3012

## What

Fixes `HeadlessExperimental.beginFrame` hanging at 60fps and other high frame rates.

## Why

Warmup always advances Chrome in 33ms steps, but the first capture timestamp was calculated from the output fps.

At 60fps, the last warmup tick is 1947ms, while the next commit tick used to jump back to about 1067ms. Chrome sees time moving backwards and `beginFrame` can stall.

## How

Keep the old timestamps when they are already safe. If the commit tick would go backwards, move the capture baseline past warmup first.

The init commit and both producer probes now use the same timestamp helpers, so they cannot calculate different values.

## Test plan

- [x] Added tests for 24, 30, 31, 32, 33, 60, 120, 240, and 59.94fps
- [x] Added coverage for the actual session baseline, commit parameters, and both producer probe paths
- [x] Engine tests: 1383 passed, 3 skipped
- [x] Producer unit tests passed
- [x] Engine and producer typechecks and builds passed
- [ ] Manual render test
2026-08-04 19:22:33 -07:00
..
2026-08-04 01:49:05 -07:00
2026-03-21 22:43:56 -07:00

@hyperframes/engine

Seekable web-page-to-video rendering engine built on Puppeteer and FFmpeg.

Framework-agnostic: works with GSAP, Lottie, Three.js, CSS animations, or any web content that implements the window.__hf seek protocol.

Install

npm install @hyperframes/engine

Requirements: Node.js >= 22, Chrome/Chromium (auto-downloaded by Puppeteer), FFmpeg

What it does

The engine opens your HTML composition in a headless Chrome instance, seeks frame-by-frame using Chrome's HeadlessExperimental.beginFrame API, captures screenshots, and encodes them into video with FFmpeg.

Key services

Service Description
browserManager Launches and pools headless Chrome instances (chrome-headless-shell)
frameCapture Manages capture sessions — seek, screenshot, buffer lifecycle
screenshotService BeginFrame-based capture with CDP (Chrome DevTools Protocol)
chunkEncoder FFmpeg encoding with chunked concat, GPU detection, faststart
streamingEncoder Pipe frames to FFmpeg in real time (no intermediate PNGs on disk)
audioMixer Parse <audio> elements and mix audio tracks via FFmpeg
videoFrameExtractor Extract frames from <video> elements for compositing
parallelCoordinator Split frame ranges across worker processes
fileServer Serve local HTML files to the browser via Hono

Usage

import {
  acquireBrowser,
  createCaptureSession,
  initializeSession,
  captureFrame,
  closeCaptureSession,
} from "@hyperframes/engine";

// 1. Launch browser
const browserLease = await acquireBrowser({ captureMode: "beginFrame" });

// 2. Open a capture session
const session = createCaptureSession({
  browser: browserLease.browser,
  url: "http://localhost:3000/my-composition.html",
  width: 1920,
  height: 1080,
  fps: 30,
});
await initializeSession(session);

// 3. Capture frames
for (let i = 0; i < totalFrames; i++) {
  await captureFrame(session, i, `/tmp/frames/frame-${i}.png`);
}

// 4. Clean up
await closeCaptureSession(session);
await browserLease.release();

Most users should use @hyperframes/producer or the hyperframes CLI instead of calling the engine directly.

Documentation

Full documentation: hyperframes.heygen.com/packages/engine