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* fix(engine): pin capture surface scale to 1 device pixel per CSS pixel
Capture reads the browser's compositor surface (`Page.captureScreenshot`
with `fromSurface: true`, and `HeadlessExperimental.beginFrame` likewise),
and that surface is rasterized at the host display's backing scale.
`page.setViewport({ deviceScaleFactor })` goes through
`Emulation.setDeviceMetricsOverride`, which only moves
`window.devicePixelRatio` on the page side — it does not resize the
surface.
On a HiDPI host every render therefore came out at twice the composition:
a 1920x1080 composition encoded to a 3840x2160 file, and no flag could
bring it down, because the pipeline's own deviceScaleFactor was already 1.
Supersampling stacked on top of it, so `--resolution landscape-4k`
produced 7680x4320 rather than 3840x2160.
Pinning the surface with `--force-device-scale-factor=1` leaves the
deliberate supersampling path (the capture clip's `scale`, from
`resolveDeviceScaleFactor`) as the only thing that multiplies output
pixels. The flag is a no-op on Linux, where the surface is already 1x, so
CI and cloud output are unchanged.
* fix(engine): drop the capture-scale comments the ratchet rejects
---------
Co-authored-by: Leo Xu <xuliyou@bytedance.com>
Co-authored-by: Miguel Ángel <miguel.sierra@heygen.com>
@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