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Use when implementing or modifying timeline playback, animation loops, or audio synchronization in the Scene Editor
기본적으로 소스를 먼저 확인하는 Prompt가 선택됩니다. 직접 명령으로 전환하거나 로컬 사본을 다운로드할 수도 있습니다.
설치 여부를 결정하기 전에 SKILL.md와 SkillsMP에 표시된 보조 파일을 읽어 보세요.
Codex 또는 Claude로 설치 이 Prompt를 복사해 Codex, Claude 또는 다른 어시스턴트에 붙여 넣으면 Skill 페이지를 검토하고 설치를 진행할 수 있습니다.
직접 명령은 검토 Prompt를 거치지 않습니다. 실행하기 전에 소스를 확인하세요.
npx skills add https://github.com/NTQ78/Todo-app --skill frontend-scene-timeline-playback명령은 한 줄로 유지됩니다. 복사하기 전에 가로로 스크롤해 전체 내용을 확인하세요.
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SKILL.md 표시 중
| name | frontend-scene-timeline-playback |
| description | Use when implementing or modifying timeline playback, animation loops, or audio synchronization in the Scene Editor |
Guidelines for implementing smooth, performant playback in the Scene Editor timeline. Covers RAF architecture, audio sync, and common pitfalls.
NEVER create multiple independent requestAnimationFrame loops for the same feature.
The Scene Editor uses a single RAF loop in PageScene_Timeline.tsx that:
performance.now() deltatimelineTimeRef.current (the source of truth)// ❌ BAD: Multiple independent RAF loops
// Each AudioLane running its own loop
useEffect(() => {
const tick = () => {
syncAudio(timelineTimeRef.current);
rafRef.current = requestAnimationFrame(tick);
};
rafRef.current = requestAnimationFrame(tick);
}, []);
// Problems:
// 1. Loops fire at different times within the same frame
// ✅ GOOD: Single RAF loop with callbacks/events
// Main loop notifies subsystems
const tick = (timestamp: number) => {
const newTime = calculateNewTime(timestamp);
timelineTimeRef.current = newTime;
// Option A: Direct call to audio manager
audioManager.syncToTime(newTime);
// Option B: Event-based notification
eventBus.emit("timelineTime", newTime);
updatePlayheadDOM(newTime);
rafRef.current = requestAnimationFrame(tick);
};
The main playback loop is in:
PageScene_Timeline.tsx:22-138 - usePageScene_Timeline_Playback hookKey refs used:
timelineTimeRef - Current playback time (source of truth during playback)playheadRef - DOM element for direct manipulationpxPerSecRef, scrollOffsetPxRef - Cached zoom/scroll values<audio> element uses browser's audio clock (independent from performance.now())audio.currentTime is a blocking seek operation that causes frame drops// ❌ BAD: Checking drift every frame and seeking
const tick = () => {
const drift = Math.abs(audio.currentTime - expectedOffset);
if (drift > 0.05) {
// 50ms threshold
audio.currentTime = expectedOffset; // CAUSES JITTER!
}
rafRef.current = requestAnimationFrame(tick);
};
// ❌ BAD: Multiple RAF loops for audio sync
// Each track has its own loop
useEffect(() => {
const tick = () => {
clips.forEach((clip) => checkAndSync(clip));
rafRef.current = requestAnimationFrame(tick);
};
// ...
}, []);
Option A: Fire-and-Forget (Simple)
// Start audio at correct offset, let it play naturally
// Accept minor drift as acceptable tradeoff
if (!clip.isPlaying && isInClip) {
clip.audio.currentTime = audioOffset;
clip.audio.play();
clip.isPlaying = true;
}
// NO drift correction during playback
Option B: Infrequent Drift Correction
// Check drift less frequently (every 30 frames ≈ 0.5s)
// Use larger threshold (200-300ms)
frameCountRef.current++;
if (frameCountRef.current % 30 === 0) {
const drift = Math.abs(audio.currentTime - expectedOffset);
if (drift > 0.2) {
// 200ms threshold
audio.currentTime = expectedOffset;
}
}
Option C: Web Audio API (Professional-grade) - IMPLEMENTED
The Scene Editor uses Web Audio API for audio playback:
// WebAudioManager singleton (webAudioManager.ts)
// - AudioContext for precise timing
// - AudioBuffer cache per file
// - GainNode per clip for instant volume changes
// - AudioBufferSourceNode per playback (fire-and-forget)
// Main RAF loop calls syncPlayback with current clip data
webAudioManager.syncPlayback(audioClipsDataRef.current, newTime, true);
// Key files:
// - webAudioManager.ts - Singleton service
// - useAudioPlayback_PageScene_Timeline.ts - Centralized hook
// - PageScene_Timeline.tsx - Integration point (line 117)
When adding new features that need time sync:
timelineTimeRef.current - Don't create your own time trackingPlayhead jitter during audio playback - RESOLVED (2025-12-18)
Root cause was multiple RAF loops (per-track) + HTML5 audio drift correction. Fixed by migrating to Web Audio API with single RAF loop architecture.
See docs/spark/frontend/my-vite-app/audio-drag-drop-spec.md Section 15 for historical context.