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James RussoandClaude Opus 4.7
ffc06827c4
* fix(engine): auto-normalize VFR video inputs to CFR before frame extraction
Screen recordings (macOS ScreenCaptureKit, QuickTime, phone videos) are
commonly variable-frame-rate. When such inputs hit the extractor's
`-ss <start> -i <video> -t <dur> -vf fps=N` pipeline, the fps filter
can emit fewer frames than requested — for a 4-second 30fps segment
starting mid-file, the output was ~90 frames instead of 120.
`FrameLookupTable.getFrameAtTime` returns null for out-of-range indices,
so the compositor held the last valid frame and the user perceived the
video as freezing. This matches the bug report from an X community post
where a user said "all of them freezes" on their screen recording scenes.
The engine already detects VFR via `metadata.isVFR` in ffprobe.ts but
never acted on it — the compiler only logged a warning. This change
mirrors the existing SDR→HDR normalization pattern: when a source is
detected as VFR, re-encode only the used segment with
`-fps_mode cfr -r <fps> -preset fast -crf 18` before extraction.
Scoping the re-encode to `[mediaStart, mediaStart+duration]` means a
30-second clip cut from a 60-minute screen recording pays ~1s of
transcode cost, not 18s. Benchmarked locally:
Baseline (current): 32-39% duplicate frames, 25% frame-count
shortfall on mid-file segments.
Tier 1 (flag changes only): ~same — fps filter issue is not flag-fixable.
Tier 2 (CFR preflight): 1.7-6% duplicate frames, correct frame
count in every scenario tested.
The compiler warning that previously told users to manually re-encode
is downgraded to `console.info` since the engine now handles it.
— Rames Jusso
* refactor(engine): clean up VFR normalization loop after review
- Drop the `vfrNormDirCreated` flag; `mkdirSync({recursive:true})` is
idempotent and cheap.
- Don't re-wrap the `VFR→CFR conversion failed` prefix — `convertVfrToCfr`
already throws a message with that label; adding it again in the catch
produced "VFR→CFR conversion failed: VFR→CFR conversion failed (exit 1)".
- Shorten the Phase 2b header comment; the function docstring above
`convertVfrToCfr` already explains the failure modes and rationale.
- Note which frame windows the VFR fixture's select filter drops so the
magic numbers are scannable.
No behavior change; 311/311 engine tests still pass.
— Rames Jusso
* test(engine): add VFR regression unit tests
Adds a describe block that synthesizes a VFR fixture via ffmpeg and asserts
the extractor produces the expected frame count (no shortfall) and no long
runs of duplicate frames — the user-visible "frozen screen recording"
symptom. Covers both a mid-file segment and the full-file case.
Guarded with describe.skipIf(!HAS_FFMPEG) because the CI Test job on
ubuntu-24.04 and the Windows test-windows job don't install ffmpeg. The
producer-level regression test in packages/producer/tests/vfr-screen-recording/
runs inside Dockerfile.test (which has ffmpeg) and is the primary CI signal
for this bug; these unit tests are supplementary coverage for local and
any ffmpeg-equipped CI environment.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
* test(producer): add vfr-screen-recording regression test
End-to-end CI regression coverage for PR #360 via the existing
regression-harness: renders a 3s composition containing a real macOS
ScreenCaptureKit clip (r_frame_rate=120, avg≈36fps) seeked to
mediaStart=1, then PSNR-compares against a committed output.mp4.
Fixture src/clip.mp4 (108 KB) is a 5-second excerpt downscaled to 480×332
with -fps_mode passthrough to preserve the VFR timestamps. Content is the
public hyperframes OSS repo root page — see NOTICE.md for provenance.
With the fix applied, all 100 PSNR checkpoints pass. With the fix reverted,
66 of 100 fail (PSNR drops from ~43 dB to ~20 dB in the duplicate-frame
windows). Tagged "regression,video,vfr" so it runs in the fast shard
of .github/workflows/regression.yml automatically.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
* test(producer): regenerate vfr-screen-recording baseline in Docker
The committed golden output.mp4 was initially rendered on the host machine;
CI runs the renderer inside Dockerfile.test with a different Chrome +
ffmpeg build, producing pixel-level drift that failed PSNR at 54/100
checkpoints (~20 dB vs 41 dB in the VFR sparse-content windows). Both
renders are valid — the VFR source has inherent sampling ambiguity in
static segments, and different Chrome/ffmpeg builds make different valid
choices.
Regenerated the baseline via `bun run docker:test:update vfr-screen-recording`
so it matches the Docker environment CI actually uses. Matches the flow
the existing sub-composition-video, hdr-pq, etc. baselines were captured
with.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
* docs: document that producer test baselines must be captured in Docker
Hit this 2026-04-21 with the vfr-screen-recording regression test:
host-generated output.mp4 baseline tripped 54/100 PSNR checkpoints in CI
because Chrome + ffmpeg drift between the host and Dockerfile.test.
Document the `bun run --cwd packages/producer docker:test:update <name>`
flow so future contributors don't repeat the mistake.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
---------
Co-authored-by: Claude Opus 4.7 (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,
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