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Vance IngallsandClaude Opus 5
0103c2459c
Findings 8-11 and 16 — the render/preview parity set. All group audio, all invisible to preview or to export alone, which is why each had a passing test beside it. 9 — The preview bus wired only the automation lane, and readElementAutomation reads data-automation, so a group's own `data-volume` never reached the graph at all: the bus stayed at unity while the render applied it. The export was ~8 dB quieter than what had been auditioned. The test named for this asserted only `resolves.not.toBeNull()`. 10 — The volume lane was scheduled on the FX chain's SOURCE, ahead of the effects, breaking the contract scheduleVolumeLane's own docstring states: "the volume lane rides the fader, after the effects — where a DAW puts it, and the order the render bakes it in". The element path honoured it; the group path did not, so any nonlinear group effect previewed differently than it rendered. Both now land on a dedicated post-FX fader node: input → chain → fader → mute → output. 11 — The bus deliberately outlives stopAll(), and groupInput early -returned on an existing entry, so after a replay or a seek no new ramps were booked and the gain held the previous pass's last value — 0 after a fade-out, i.e. silent for the rest of the session. It re-anchors once per play generation now (ElementFxHandle gains `reanchor`), and the record keeps its `fx` handle so setRate can re-aim a group's automation, which its docblock already claimed it did. 8 — The sub-mix summed members at unity (normalize=0) into a pcm_s16le intermediate, so an over-unity sum hard-clipped at ±1 BEFORE the group's FX and fader ran: pulling the fader down, or the Giant preset's compressor, then operated on distortion. The intermediate is float now. Both downstream readers already took float; applyVolumeEnvelopeToWav did not, and does now, so a group's envelope is still baked sample-accurately rather than silently degrading to the expression path. The new level test is the one that matters here: EVERY tone in that file is built on ffmpeg's `sine` source, which peaks at ~0.125 full scale, so nothing in the suite could reach a clip whatever gain it asked for. `writePeakTone` states the amplitude outright, and the test fails against the 16-bit intermediate. 16 — mixGroupMembers forked mixAudioTracks' filter build and dropped its automation-degradation retry, so a member envelope past this ffmpeg build's expression limits failed the whole composition's audio where an ungrouped one degrades to base volume with a warning. The retry is back, reported on a successful result the same way. The group track is also pushed with its volumeKeyframes when the envelope could not be baked, instead of losing the group's automation silently. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.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