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https://github.com/heygen-com/hyperframes.git
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Miguel Ángel
3a72aa528d
## Summary Fixes #1317 — systematic duplicate+skip video frames when clip `data-start` is aligned to the output frame grid. ### Root cause `Math.floor(localTime * fps)` in `getFrameAtTime` produces off-by-one errors when the product lands exactly on an integer boundary due to IEEE 754 float noise. For example, `0.28 * 25 === 6.999999999999999` instead of `7`, causing `Math.floor` to return 6 (duplicate of previous frame) instead of 7. ### Fix 1. Add `1e-9` epsilon before flooring: `Math.floor(localTime * fps + 1e-9)` — nudges boundary values like `6.999999` to `7.000000` without affecting mid-frame values. 2. Include `mediaStart` in the frame index computation so trimmed clips (`data-media-start`) map to the correct extracted frames. Both call sites fixed: `getFrameAtTime()` (public API) and the `FrameLookupTable.getFramesAtTime()` bulk lookup. ### Reporter's measurements (before fix) | Case | Duplicates (of 351 frames) | |---|---| | Source file | 1 | | data-start="0" | 14 | | data-start="230.44" (production) | 127 | | data-start="0.02" (half-frame offset workaround) | 1 | ## Test plan - [x] 4 new regression tests for IEEE 754 boundary precision - [x] No duplicate frames when data-start is grid-aligned (25fps) - [x] Monotonically increasing frame indices across 100 frames - [x] Correct frame at the `0.28 * 25` boundary (frame 7, not 6) - [x] `mediaStart` correctly offsets frame index - [x] Typecheck clean
@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