Files
hyperframes/packages/engine
Vance Ingalls e37ebe7999 fix(producer,engine): gate drawelement on ancestor background-image + tail verify sample (#2247)
## What

Two fixes from adversarial testing of the DE parallel router (10 hostile comps, routed vs screenshot-baseline PSNR). The router itself held — both bugs are in general drawElement fast capture, and one slipped past self-verify.

### 1. Compile gate: ancestor background-image (`producer`)

`drawElementService`'s per-frame ancestor fill replicates what lies behind the captured subtree by walking up the DOM for the nearest non-transparent **`backgroundColor`**. A background-**image** (`linear-gradient`, `url()`) on `body`/`html`/a wrapper reads as transparent in that scan, so a deeper ancestor's solid color paints instead wherever the subtree leaves pixels uncovered.

Measured repro: body `linear-gradient` + html solid color + an element shrinking late in the comp → DE paints the html purple instead of the body gradient. 30.9 dB min frame vs baseline, visually unmistakable. Identical damage single-worker and parallel — general DE bug, in every wild DE render matching this (very common) authoring pattern.

Fix: `detectAncestorBackgroundImage()` in the compiler (DOM-aware — inline styles on the root's ancestor chain + `<style>` rules resolved via `querySelectorAll`, so class-selected wrappers are covered; backgrounds *inside* the root are deliberately not matched). New compile gate `ancestor_background_image`, same shape as the 3D/mix-blend gates, bypass `HF_FAST_CAPTURE_ANCESTOR_BG=true`.

### 2. Self-verify tail sample (`engine`)

The verify grid sampled at `(i+1)/(k+1)` → [20/40/60/80]% of the timeline. The damage above starts at ~79% and peaks after the last sample — verification **passed** on output that bottomed at 30.9 dB (threshold 32 dB would have caught it, it just never looked there).

Fix: `computeDeVerifySampleFractions()` — first k−1 samples evenly spaced, last pinned at 95%. Default k=4 grid becomes [25/50/75/95]%. Kills the whole late-onset damage class, not just this repro.

## Validation

- Repro comp (body gradient + shrink reveal): now gates → baseline route, 54.7 dB avg vs ground truth (was 41.6 avg / 30.9 min with the purple surround)
- Control comp (nested stacked fades, routed): still routes, verify grid `[90, 180, 270, 342] of 360`, passes, 60.6 dB avg — unchanged
- Full adversarial matrix context: 6/10 comps routed clean (49–68 dB min), blend/3D gated correctly, animated-canvas damage caught by verify at 16.5 dB with clean revert, video comps route legitimately (frames pre-extracted)
- Tests: 7 new detection cases (`htmlCompiler.test.ts`), 5 new grid cases (`frameCapture-verifySampleFractions.test.ts`); `compileStage.test.ts` + `frameCapture.test.ts` suites green

🤖 Generated with [Claude Code](https://claude.com/claude-code)
2026-07-11 14:13:09 -07:00
..
2026-07-11 15:59:07 -04:00
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,
  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