Miguel Ángel
f1a37400b4
## Summary Fixes three audio-sync defects in the studio preview plus a small UX improvement. All four land in one commit so the PR stays aligned with one bug fix per commit. ### 1\. Silent / very-late first play on slow-loading audio (`packages/core/src/runtime/media.ts`) `syncRuntimeMedia`'s old flow — when it hit `readyState < HAVE_FUTURE_DATA` — called `el.load()` and attached a `canplay` listener to retry `play()`. Two real problems, neither of which is "lost user activation" (the sync runs from a 50 ms `setInterval`, well outside any gesture window): - `bindMediaMetadataListeners` already sets `preload="auto"` and calls `el.load()` at runtime init. The sync's duplicate `el.load()` aborts that in-flight fetch and restarts from zero — on slow networks this delayed playback by seconds, which users perceived as "silent until a second click." - The `canplay` listener was racy: the event can fire between `load()` and `addEventListener`, leaving the element wedged. `HTMLMediaElement.play()` is already spec'd to queue playback until data arrives, so we can unconditionally call it. Drop the `readyState` gate, the redundant `load()`, and the `canplay` listener. Also dedup in-flight `play()` calls with a `WeakSet` (cleared on `playing`/`pause`/`error`) — without it the 50 ms poll fires 20–40 spurious calls per element during buffer, each silencing real `AbortError`/`NotAllowedError` diagnostics in the `.catch`. ### 2\. Audible stutter on rapid pause/play (`packages/core/src/runtime/media.ts`) The 0.3 s drift-seek threshold fired on nearly every toggle because pause/play ordering between timeline and media produces 0.1–0.4 s of transient drift. Each forced `el.currentTime = relTime` drops `readyState` and surfaces as a `waiting` event the user hears as a stutter. Threshold raised to 0.5 s. ### 3\. Skipped words on cold first play (`packages/core/src/runtime/media.ts`) Even with 0.5 s, drift grew past 0.5 s during initial buffering while the audio element was stuck at `currentTime = 0`. The old logic would then force-seek audio forward and the user missed the opening of the narration. Fix distinguishes drift that grows _gradually_ (buffer catch-up, ~16 ms/tick) from drift that _jumps_ in one tick (a scrub). Only jumps, first-tick clip activation, or catastrophic drift (>3 s) trigger a resync. Inline tradeoff note in code: strictly lip-synced dialogue would want a tighter threshold (~0.15 s) outside a 500 ms toggle window — deferred to a future PR. ### 4\. "Loading assets…" overlay in the studio preview (`packages/studio/src/player/components/Player.tsx`) Spinner while every timed `<audio>`/`<video>` has enough buffered data and every Lottie animation is loaded. Preserves the previous overlay state on cross-origin / transient-DOM catches so a brief access failure doesn't flicker, and logs `console.debug` when the 10 s safety cap trips so a stuck asset is diagnosable. Lottie readiness handles both `lottie-web` (`isLoaded`) and `@dotlottie/player-component` (`totalFrames > 0`), with an inline `@see` pointing to `packages/core/src/runtime/adapters/lottie.ts` so the two sites stay in sync. ## Verification - 456 core tests pass; 34 in `media.test.ts` cover synchronous play, preload nudge, play-request dedup, offset-jump vs gradual drift, first-tick hard-sync, catastrophic-drift safety valve, and inactive-clip baseline reset. - Full monorepo build green (`bun run build`), typecheck clean, lint/format clean. - End-to-end with agent-browser against a composition that uses a 50 s voiceover plus multiple sub-composition video clips. Four scenarios, all pass: | Scenario | Metric | Result | | --- | --- | --- | | Normal first play | Audio plays from click, smooth progression | ✅ | | Cold play (forced unbuffered) | First `play` event fires at `ct: 0` — no word-skip | ✅ | | Rapid pause/play (12 toggles) | `waiting` events: 1 (was 40+ bursts) | ✅ | | Scrub mid-playback | Lands exactly at target frame | ✅ | ## Files changed - `packages/core/src/runtime/media.ts` — unconditional synchronous `play()`; play-request dedup WeakSet; offset-jump-only drift correction; 0.5 s threshold; first-tick hard-sync; catastrophic-drift safety valve. - `packages/core/src/runtime/media.test.ts` — coverage for the above plus the gradual-drift cold-play case, scrub offset-jump, in-flight dedup, and inactive-clip baseline reset. - `packages/core/src/runtime/adapters/lottie.ts` — exported `isLottieAnimationLoaded` helper documenting the two supported player shapes. - `packages/studio/src/player/components/Player.tsx` — loading-assets overlay with cached-return catch, timeout debug log, and the Lottie readiness check. ## Follow-ups (deferred) - Tight-threshold short-window drift correction for lip-synced dialogue. - A perf-regression test that fails on `waiting`\-event resurgence. ## Test plan - [x] `hyperframes preview` a composition with audio, `Cmd+Shift+R`, click play immediately — audio starts from the very beginning, no skipped words. - [x] Rapidly pause/play the preview — audio stays smooth (no stutter, no `waiting` events). - [x] Cold-load a composition — "Loading assets…" overlay appears and disappears once media buffers. - [ ] Scrub the timeline mid-playback — audio follows the scrub, lands on frame.
Write HTML. Render video. Built for agents.
Hyperframes is an open-source video rendering framework that lets you create, preview, and render HTML-based video compositions — with first-class support for AI agents.
Quick Start
Option 1: With an AI coding agent (recommended)
Install the HyperFrames skills, then describe the video you want:
npx skills add heygen-com/hyperframes
This teaches your agent (Claude Code, Cursor, Gemini CLI, Codex) how to write correct compositions and GSAP animations. In Claude Code, the skills register as slash commands — invoke /hyperframes to author compositions, /hyperframes-cli for CLI commands, and /gsap for animation help.
Try it: example prompts
Copy any of these into your agent to get started. The /hyperframes prefix loads the skill context explicitly so you get correct output the first time.
Cold start — describe what you want:
Using
/hyperframes, create a 10-second product intro with a fade-in title, a background video, and background music.
Warm start — turn existing context into a video:
Take a look at this GitHub repo https://github.com/heygen-com/hyperframes and explain its uses and architecture to me using
/hyperframes.
Summarize the attached PDF into a 45-second pitch video using
/hyperframes.
Turn this CSV into an animated bar chart race using
/hyperframes.
Format-specific:
Make a 9:16 TikTok-style hook video about [topic] using
/hyperframes, with bouncy captions synced to a TTS narration.
Iterate — talk to the agent like a video editor:
Make the title 2x bigger, swap to dark mode, and add a fade-out at the end.
Add a lower third at 0:03 with my name and title.
The agent handles scaffolding, animation, and rendering. See the prompting guide for more patterns.
Option 2: Start a project manually
npx hyperframes init my-video
cd my-video
npx hyperframes preview # preview in browser (live reload)
npx hyperframes render # render to MP4
hyperframes init installs skills automatically, so you can hand off to your AI agent at any point.
Requirements: Node.js >= 22, FFmpeg
Why Hyperframes?
- HTML-native — compositions are HTML files with data attributes. No React, no proprietary DSL.
- AI-first — agents already speak HTML. The CLI is non-interactive by default, designed for agent-driven workflows.
- Deterministic rendering — same input = identical output. Built for automated pipelines.
- Frame Adapter pattern — bring your own animation runtime (GSAP, Lottie, CSS, Three.js).
How It Works
Define your video as HTML with data attributes:
<div id="stage" data-composition-id="my-video" data-start="0" data-width="1920" data-height="1080">
<video
id="clip-1"
data-start="0"
data-duration="5"
data-track-index="0"
src="intro.mp4"
muted
playsinline
></video>
<img
id="overlay"
class="clip"
data-start="2"
data-duration="3"
data-track-index="1"
src="logo.png"
/>
<audio
id="bg-music"
data-start="0"
data-duration="9"
data-track-index="2"
data-volume="0.5"
src="music.wav"
></audio>
</div>
Preview instantly in the browser. Render to MP4 locally or in Docker.
Catalog
50+ ready-to-use blocks and components — social overlays, shader transitions, data visualizations, and cinematic effects:
npx hyperframes add flash-through-white # shader transition
npx hyperframes add instagram-follow # social overlay
npx hyperframes add data-chart # animated chart
Browse the full catalog at hyperframes.heygen.com/catalog.
Documentation
Full documentation at hyperframes.heygen.com/introduction — Quickstart | Guides | API Reference | Catalog
Packages
| Package | Description |
|---|---|
hyperframes |
CLI — create, preview, lint, and render compositions |
@hyperframes/core |
Types, parsers, generators, linter, runtime, frame adapters |
@hyperframes/engine |
Seekable page-to-video capture engine (Puppeteer + FFmpeg) |
@hyperframes/producer |
Full rendering pipeline (capture + encode + audio mix) |
@hyperframes/studio |
Browser-based composition editor UI |
@hyperframes/player |
Embeddable <hyperframes-player> web component |
@hyperframes/shader-transitions |
WebGL shader transitions for compositions |
Skills
HyperFrames ships skills that teach AI agents framework-specific patterns that generic docs don't cover.
npx skills add heygen-com/hyperframes
| Skill | What it teaches |
|---|---|
hyperframes |
HTML composition authoring, captions, TTS, audio-reactive animation, transitions |
hyperframes-cli |
CLI commands: init, lint, preview, render, transcribe, tts, doctor |
hyperframes-registry |
Block and component installation via hyperframes add |
gsap |
GSAP animation API, timelines, easing, ScrollTrigger, plugins, React/Vue/Svelte, performance |
Contributing
See CONTRIBUTING.md for guidelines.