Follow-up to PR #298 addressing @jrusso1020's review. Each item below maps to a point in his comment. ## Significant ### 1\. Drift threshold 150 ms → 50 ms _mirrorParentMediaTime_ was too loose for lip-synced talking-head content. ITU-R BT.1359 puts A/V perceptibility at ±45 ms; 150 ms sat well inside the "unacceptable" zone. Dropped to 50 ms, extracted as a static constant for clarity. **Verified live on factory-series-c-video (agent-browser):** steady-state offset under parent ownership sampled five times over 400 ms = `[35.7, 33.5, 31.2, 27.2, 36.9]` ms — below the perceptibility floor. Before this PR the same measurement could drift up to 150 ms before correction. ### 2\. Dynamic sub-composition media proxies Under parent ownership, a sub-composition that attaches a new `<audio data-start>` mid-playback was correctly silenced in the iframe (sticky `outputMuted`) but had no parent-frame counterpart to play → silent hole in the audio track. Added a `MutationObserver` on the iframe body watching for `audio[data-start]` / `video[data-start]` additions. New elements are adopted through the same `_adoptIframeMedia` helper the initial scan uses, and if parent ownership is already active the new proxy gets its `currentTime` mirrored and `play()` called immediately (gated on `!this._paused`). Observer disconnects on iframe reload + component disconnect. ### 3\. `bridgeMuted` sticky in `syncRuntimeMedia` The asymmetry James flagged: `outputMuted` was sticky per-tick, `bridgeMuted` was one-shot via `onSetMuted`. A sub-composition activating after a user mute would briefly play at author volume before the next bridge message. `syncRuntimeMedia` now accepts `userMuted` and the per-clip loop uses a single combined `shouldMute` gate. One invariant, two inputs. ### 4\. Reset `_audioOwner` on iframe reload The latch never cleared. On composition switch the player would stay in `parent` ownership against a fresh runtime that hadn't received `set-media-output-muted` and whose autoplay-blocked latch was clean — a brief double-audio window until the next `NotAllowedError` re-promoted (idempotently). `_onIframeLoad` now resets `_audioOwner = "runtime"`, pauses any parent proxies, and disconnects the old MutationObserver before a fresh one attaches to the new document. If the player had been in `parent` ownership, a corresponding `audioownershipchange` event fires with `reason: "iframe-reload"`. ## Worth addressing ### 5\. Promotion → observable event + reason Promotion was invisible. Added `CustomEvent("audioownershipchange", { detail: { owner, reason } })` fired on every owner transition. `reason` is either `"autoplay-blocked"` (promote → parent) or `"iframe-reload"` (reset → runtime). Gives host apps an SLO-ready signal for "% of sessions in parent ownership" without exposing internal state. **Verified live:** dispatching a synthetic `media-autoplay-blocked` in the live studio produced `{ owner: "parent", reason: "autoplay-blocked" }` on the web component exactly once. ### 6\. Parent proxy play() rejection → `playbackerror` event Previously swallowed silently. Now re-emitted as `CustomEvent("playbackerror", { detail: { source: "parent-proxy", error } })` so embedding apps can recover or fall back. ### 7\. Mobile verification on real hardware Tested with a tunnel in a real iOS device. ## Test gaps (from review) - `userMuted` stickiness (mirror of the existing `outputMuted` test). - **OR invariant** between `outputMuted` and `userMuted` — explicit test that setting one false while the other is true keeps `el.muted === true`. - **Contract pin:** `syncRuntimeMedia` fires `onAutoplayBlocked` on **every** rejection (no internal dedupe) — so a future refactor can't quietly move the latch and break the caller's posting logic. - **Caller-side latch pattern:** a 5-rejection simulation with the init.ts-style wrapper posts exactly once. - **`audioownershipchange`** **dispatch** on promotion + once per transition (no duplicate on idempotent re-promote). - **Mid-playback promotion:** `_paused = false` at flip time fires `_playParentMedia` immediately. - **`playbackerror`** **surface** on parent proxy rejection with the right `source` tag. ## Minor - One-line comment on `_promoteToParentProxy` explaining the `postMessage` async race (the mute lands after ~one message-loop tick; the autoplay gate that triggered promotion keeps the iframe rejecting `play()` during that window, so the double-play bug doesn't reappear). ## What's good (from the review) Kept as-is — noted for posterity: - `muted` vs `volume` framing (orthogonal channels). - Probing reality via `NotAllowedError` instead of `matchMedia('(pointer: coarse)')` / UA sniffing. - Two orthogonal mute channels. - Backwards compat (new actions / messages safely ignored by either side). ## Test results - `packages/core/src/runtime/media.test.ts` — **42 tests pass** (+4 new: `userMuted` sticky, OR invariant, fires-every-rejection, caller-latch dedupe) - `packages/core/src/runtime/bridge.test.ts` — **15 tests pass** - `packages/player/src/hyperframes-player.test.ts` — **26 tests pass** (+3 new: `audioownershipchange` dispatch, mid-playback promotion, `playbackerror` surface) - Typecheck green on `core` + `player` - `tsup` build green on `core` / `player` / `cli` - Live factory-series-c-video repro via agent-browser: runtime ownership still zero `volumechange` thrash, zero `PARENT.play()` calls; parent ownership measures 27–37 ms steady-state drift, well inside the 50 ms threshold. ## Test plan - [x] Unit tests (83 total across touched files) - [x] Typecheck clean - [x] Build clean - [x] Live studio repro on factory-series-c-video: runtime path unchanged, parent path drift tightened - [x] `audioownershipchange` event fires with correct detail on synthetic autoplay block - [x] Physical iOS / Android device verification (unchanged since #298)
@hyperframes/player
Embeddable web component for playing HyperFrames compositions. Zero dependencies, works with any framework.
Install
npm install @hyperframes/player
Or load directly via CDN:
<script src="https://cdn.jsdelivr.net/npm/@hyperframes/player"></script>
Usage
<hyperframes-player src="./my-composition/index.html" controls></hyperframes-player>
The player loads the composition in a sandboxed iframe, auto-detects its dimensions and duration, and scales it responsively to fit the container.
With a framework
import "@hyperframes/player";
// The custom element is now registered — use it in your markup
// React: <hyperframes-player src="..." controls />
// Vue: <hyperframes-player :src="url" controls />
Poster image
Show a static image before playback starts:
<hyperframes-player
src="./composition/index.html"
poster="./thumbnail.jpg"
controls
></hyperframes-player>
Attributes
| Attribute | Type | Default | Description |
|---|---|---|---|
src |
string | — | URL to the composition HTML file |
audio-src |
string | — | Audio URL for parent-frame playback (mobile) |
width |
number | 1920 | Composition width in pixels (aspect ratio) |
height |
number | 1080 | Composition height in pixels (aspect ratio) |
controls |
boolean | false | Show play/pause, scrubber, and time display |
muted |
boolean | false | Mute audio playback |
poster |
string | — | Image URL shown before playback starts |
playback-rate |
number | 1 | Speed multiplier (0.5 = half, 2 = double) |
autoplay |
boolean | false | Start playing when ready |
loop |
boolean | false | Restart when the composition ends |
Mobile audio
Mobile browsers block audio.play() inside iframes when the user gesture happened in the parent frame (the User Activation spec does not propagate activation across frame boundaries via postMessage).
The player handles this automatically for same-origin iframes (the default — sandbox includes allow-same-origin):
- When the composition is ready, the player extracts all timed media (
audio[data-start],video[data-start]) from the iframe DOM and creates parent-frame copies. - The iframe originals are disabled (
srcanddata-startremoved) so the runtime doesn't try to play them. - When
play()is called (from a user gesture), parent media.play()runs synchronously in the gesture call stack, satisfying mobile autoplay policy. - Both parent media and the GSAP timeline start simultaneously and free-run — no active sync needed since both are real-time systems.
No changes are required by consumers — this works out of the box.
The optional audio-src attribute can be used to start preloading a primary audio track before the iframe loads (useful on slow connections), but is not required for mobile playback.
JavaScript API
const player = document.querySelector("hyperframes-player");
// Playback
player.play();
player.pause();
player.seek(2.5); // jump to 2.5 seconds
// Properties
player.currentTime; // number (read/write)
player.duration; // number (read-only)
player.paused; // boolean (read-only)
player.ready; // boolean (read-only)
player.playbackRate; // number (read/write)
player.muted; // boolean (read/write)
player.loop; // boolean (read/write)
// Inner iframe access (for advanced consumers — see "Advanced: iframe access" below)
player.iframeElement; // HTMLIFrameElement (read-only)
Advanced: iframe access
The composition runs inside a sandboxed <iframe> in the player's Shadow DOM. For most use cases you don't need direct access — the JavaScript API above is enough. But if you're building an editor, recorder, or custom timeline that needs to inspect the composition's DOM or read its __player / __timelines runtime objects, use the iframeElement getter:
const player = document.querySelector("hyperframes-player");
const iframe = player.iframeElement;
// Now you can reach into the composition's DOM and runtime
iframe.contentDocument.querySelectorAll("[data-composition-id]");
iframe.contentWindow.__timelines;
This is the canonical way to bridge the player into tools like @hyperframes/studio. The studio exports a resolveIframe helper that works with both iframe refs and web-component refs:
import { useTimelinePlayer, resolveIframe } from "@hyperframes/studio";
const { iframeRef } = useTimelinePlayer();
const player = document.createElement("hyperframes-player");
player.setAttribute("src", src);
container.appendChild(player);
// Forward the inner iframe so useTimelinePlayer can drive play/pause/seek.
iframeRef.current = resolveIframe(player);
React: declarative ref pattern
If you prefer JSX over imperative element creation, attach a ref directly to the web component and resolve the iframe inside an effect:
import "@hyperframes/player";
import type { HyperframesPlayer } from "@hyperframes/player";
import { useTimelinePlayer, resolveIframe } from "@hyperframes/studio";
function StudioPreview({ src }: { src: string }) {
const { iframeRef, onIframeLoad } = useTimelinePlayer();
const playerRef = useRef<HyperframesPlayer>(null);
useEffect(() => {
iframeRef.current = resolveIframe(playerRef.current);
});
return <hyperframes-player ref={playerRef} src={src} onLoad={onIframeLoad} />;
}
Heads up — common gotcha
If you pass the
<hyperframes-player>element itself (notiframeElement) into a hook that expects an<iframe>, every.contentWindow/.contentDocumentaccess returnsnullbecause the iframe lives inside the player's Shadow DOM. Always extractiframeElementfirst, or useresolveIframefrom@hyperframes/studiowhich handles both iframe and web-component hosts transparently.
Events
| Event | Detail | Fired when |
|---|---|---|
ready |
{ duration } |
Composition loaded and duration determined |
play |
— | Playback started |
pause |
— | Playback paused |
timeupdate |
{ currentTime } |
Playback position changed (~10 fps) |
ended |
— | Reached the end (when not looping) |
error |
{ message } |
Composition failed to load |
player.addEventListener("ready", (e) => {
console.log(`Duration: ${e.detail.duration}s`);
});
player.addEventListener("ended", () => {
console.log("Done!");
});
Sizing
The player fills its container and scales the composition to fit while preserving aspect ratio. Set a size on the element or its parent:
hyperframes-player {
width: 100%;
max-width: 800px;
aspect-ratio: 16 / 9;
}
The width and height attributes define the composition's native resolution for aspect ratio calculation — they don't set the player's display size.
How it works
The player renders compositions in a sandboxed <iframe> inside a Shadow DOM. It communicates with the HyperFrames runtime via postMessage. If the composition has GSAP timelines (window.__timelines) but no runtime, the player auto-injects it from CDN.
Distribution
| Format | File | Use case |
|---|---|---|
| ESM | hyperframes-player.js |
Bundlers (Vite, webpack, etc.) |
| CJS | hyperframes-player.cjs |
Node.js / require() |
| IIFE | hyperframes-player.global.js |
<script> tag, CDN |
All formats are minified with source maps. TypeScript definitions included.
License
MIT