Function syncMediaForCurrentState

packages/core/src/runtime/init.ts:1657–1771

()

  };

  const syncMediaForCurrentState = () => {
    const resolveMediaCompositionContext = (element: HTMLVideoElement | HTMLAudioElement) => {
      const compositionRoot = element.closest("[data-composition-id]");
      const inheritedStart = compositionRoot ? resolveStartForElement(compositionRoot, 0) : null;
      // Media sync follows the authored host window, matching visibility for
      // authored composition hosts. Live child timeline duration only fills in
      // when no authored timing exists, so seeks clamp against host clip timing.
      const inheritedDuration = compositionRoot
        ? resolveDurationForElement(compositionRoot, { includeAuthoredTimingAttrs: true })
        : null;
      return { compositionRoot, inheritedStart, inheritedDuration };
    };
    const cache = refreshRuntimeMediaCache({
      shouldIncludeElement: (element) =>
        element.hasAttribute("data-start") ||
        Boolean(resolveMediaCompositionContext(element).compositionRoot),
      resolveStartSeconds: (element) => {
        const context = resolveMediaCompositionContext(
          element as HTMLVideoElement | HTMLAudioElement,
        );
        return resolveMediaStartSeconds(element, context.inheritedStart ?? 0);
      },
      resolveDurationSeconds: (element) => {
        const context = resolveMediaCompositionContext(element);
        const start = resolveMediaStartSeconds(element, context.inheritedStart ?? 0);
        const mediaStart =
          Number.parseFloat(element.dataset.playbackStart ?? element.dataset.mediaStart ?? "0") ||
          0;
        const hostRemaining =
          context.inheritedStart != null &&
          context.inheritedDuration != null &&
          context.inheritedDuration > 0
            ? Math.max(0, context.inheritedStart + context.inheritedDuration - start)
            : null;
        const sourceDuration =
          Number.isFinite(element.duration) && element.duration > mediaStart
            ? Math.max(0, element.duration - mediaStart)
            : null;
        // The element's own data-duration is an explicit clip-length trim
        // (the studio writes it when you drag the clip edge). It must bound
        // playback so a trimmed track stops at its edge instead of running on
        // to the source-file or host-composition end. Absent → no cap (an
        // untrimmed clip plays its natural source length).
        const ownDuration = Number.parseFloat(element.dataset.duration ?? "");
        const explicitDuration =
          Number.isFinite(ownDuration) && ownDuration > 0 ? ownDuration : null;
        const candidates = [sourceDuration, hostRemaining, explicitDuration].filter(
          (value): value is number => value != null,
        );
        return candidates.length > 0 ? Math.min(...candidates) : null;
      },
    });
    // Attach probed volume keyframes to clips so syncRuntimeMedia can use the
    // same envelope the renderer uses instead of tracking GSAP-change diffs.
    for (const clip of cache.mediaClips) {
      const kf = volumeKeyframeCache.get(clip.el as HTMLMediaElement);
      if (kf) clip.volumeKeyframes = kf;
    }