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Miguel Ángel
d3c333b383
Preview audio with GSAP volume fades (e.g. data-volume="0" with a
gsap.to("#bgm", {volume:0.25, ...})) played ~1s then silenced. Root
cause: syncRuntimeMedia used fallbackAuthorVolume (data-volume) on the
first tick after a clip became active, clobbering the GSAP-seeked value.
The single-clock transport seeks GSAP before syncRuntimeMedia runs, so
el.volume already holds the animated value — we just need to trust it.
Fix — three layers, matching the renderer's approach (PR #1117):
1. First-tick tracking: on the first tick a clip is active
(previousRuntimeVolume===undefined), use currentElementVolume (GSAP's
seeked value) instead of fallbackAuthorVolume. In production the
transport always seeks GSAP before syncRuntimeMedia, so el.volume is
already at the correct animated position.
2. Probed keyframes: new probeElementVolumeKeyframes() runs the same
offline probe the renderer uses (discoverAudioVolumeAutomationFromTimeline)
directly in the browser. init.ts calls probeAndCacheElementVolume() when
an element is bound and a timeline is available. When keyframes are present,
syncRuntimeMedia drives volume from the interpolated envelope — no
GSAP-change tracking needed, no first-tick edge case, same data source
as the renderer.
3. Shared utilities: normaliseEnvelope(), interpolateVolumeGain(), and
probeAndCacheElementVolume() extracted to mediaVolumeEnvelope.ts and
exported from @hyperframes/core/media-volume-envelope. The engine's
audioVolumeEnvelope.ts imports from there — no duplicate logic between
the renderer and the new preview path.
Fallow audit exits non-zero on inherited complexity/duplication in init.ts
functions that shifted line numbers (applyClipLayout, transportTick, etc.),
unchanged by this PR — same known false-positive pattern noted in #1117.
Lint, format, typecheck, and unit tests all pass.
53 core/media tests pass (3 updated to pre-set el.volume to match the
runtime's bindMediaMetadataListeners — corrects a missing setup step).
audioVolumeEnvelope tests (6) still pass.