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Vance Ingalls
bfa27381e1
The internal AbortController exists so a fatal FX error can cancel in-flight
ffmpeg before the finally-block deletes workDir. It reached the entry guard and
applyAudioFxChain, and nothing else: the trim, the video extract and the
download were all still handed the CALLER's signal. So `internalController
.abort()` cancelled nothing, and the `rmSync(workDir, { recursive: true })`
immediately after it ran while those children were still writing into the
directory.
Concretely: track A's FX render fails while track B is mid-trim, with no
external cancellation. B's ffmpeg keeps writing `${id}-trimmed.wav` into an
unlinked directory until it finishes. The comment above the controller
describes a mechanism that was never wired to the processes it names.
The download also had no signal at all, though downloadToTemp accepts one.
No test: the three changes are which variable is passed to a child process
helper, and observing the difference means driving real ffmpeg to the point of
cancellation. The old wiring's inertness is provable by reading — the caller's
signal is never aborted by this function — and the new wiring is the same three
calls with the controller the function already built.
@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
Related packages
@hyperframes/core— types, parsers, frame adapters@hyperframes/producer— high-level render pipeline built on this enginehyperframes— CLI