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Extends RenderConfig.format with "png-sequence" and patches two correctness
gaps so the existing "webm" / "mov" values actually preserve the alpha
channel end-to-end.
Engine fixes:
- screenshotService.pageScreenshotCapture: drop optimizeForSpeed for PNG
captures. The fast path uses an alpha-unaware codec that crushes real
alpha values; kept for opaque jpeg captures where it is harmless.
- frameCapture: replace the inline setDefaultBackgroundColorOverride
block (which fired pre-navigation and was reset by page.goto) with a
proper initTransparentBackground() call inside initializeSession,
after the window.__hf readiness poll. This also injects the
html/body/[data-composition-id]{background:transparent !important}
stylesheet so compositions with custom body / #root backgrounds do not
defeat the override. Wired into both screenshot-mode and beginframe-mode
branches.
Producer:
- RenderConfig.format extended to "mp4" | "webm" | "mov" | "png-sequence"
with full JSDoc.
- Streaming encode is bypassed for png-sequence (frames go straight to
disk). FORMAT_EXT extended.
- New Stage-5 png-sequence branch: mkdir outputPath, copy captured PNGs as
frame_NNNNNN.png, copy audio.aac sidecar when audio is present.
- Stage-6 mux/faststart and the debug copy are wrapped in !isPngSequence.
- README.md: new "Transparent Video Output" section.
Tests:
- New fixture tests/transparency-regression/ tagged "transparency".
- New tsx script src/transparency-test.ts asserts pixel-level alpha for
webm + png-sequence outputs. Wired as "test:transparency".
- Default "test" / "test:update" scripts pass --exclude-tags transparency
so the golden-MP4 harness ignores the new fixture.
Verified locally on macOS arm64: typecheck clean across engine + producer,
producer renderOrchestrator vitest 10/10, transparency-test passes for
both webm and png-sequence with end-to-end pixel assertions.
@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,
releaseBrowser,
createCaptureSession,
initializeSession,
captureFrame,
closeCaptureSession,
} from "@hyperframes/engine";
// 1. Launch browser
const browser = await acquireBrowser({ captureMode: "beginFrame" });
// 2. Open a capture session
const session = createCaptureSession({
browser: browser.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 releaseBrowser(browser);
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