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Vance IngallsandClaude Sonnet 5 99f42be04c feat(engine): render grouped audio through a summed, FX-processed bus (#3289)
* feat(core): route grouped audio through a group bus in preview

An audio element carrying `data-audio-group` no longer lands its gain on
the master bus directly — it feeds a per-group `GainNode` (built lazily on
first use, one per group id) which itself feeds master, so members of the
same group sum before the ear, ready for a group-level FX chain and
volume/mute in later steps. An id with no matching `<hf-audio-group>`
element still gets a plain, unprocessed bus rather than losing the track.

The group's own chain and volume lane are wired through the same
`attachElementFxChain`/`scheduleVolumeLane` every element already uses,
against the group's clock — composition time (design doc §1.3), since a
group has no `data-start` and a missing one parses as 0. The bus persists
across `stopAll()` (mirroring `_masterGain`'s own lifecycle) so replaying a
group does not rebuild its chain; only `destroy()` disposes it.

Render is untouched — stays flat until B4; `audio-groups` is still a 0%
canary so nothing ships this to a real composition without hand-authoring
`data-audio-group`.

Also: `audioGroupOf` (B1) crashed on any element lacking a real `tagName`/
`getAttribute` — exactly the shape of most `HTMLMediaElement` test doubles
in this suite, including this file's own `mockEl`. Made it tolerant, same
style as `readChain`'s existing guard in `runtime/audioFx.ts`.

`schedulePlayback` was already 110 lines pre-existing before this diff;
extracted `resolveDestination` and `handleSourceEnded` to shrink it to 92,
then suppressed the remainder (inherently sequential graph wiring, not a
decision tree) per the same precedent B2 used on `TimelineLogicalRow`.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

* feat(studio,lint): carve targets voiceover groups — always, when plural

Plural voiceover carve now targets a group instead of naming each clip:
`resolveCarveSourceIds` (core `audioGroups.ts`) expands a group id to its
current members at analysis time, so a clip added to the group later is
covered without touching `sources`. The picker (`useFxCarve.ts`) offers a
grouped voice as one option instead of one row per member, tests overlap
as a union of member spans (a group overlaps the bed if ANY member does),
and prefers a qualifying group over its individual members in
`autoSourceIds`.

Picking two or more ungrouped voice clips in the carve flow now mints a
group behind them (`mintGroupId`, de-duped against every id in the
document) and writes `data-audio-group` on each picked clip atomically,
one undo entry — `createAudioGroupAndAssignMembers` in
`timelineTrackVisibility.ts` copies `setElementsHidden`'s multi-target
write shape. The DSP is untouched: `mixCarveSources` already sums
multiple sources correctly (verified in the design doc's own
investigation) — this only fixes the picker.

New lint rule `audio_carve_ungrouped_sources` (`packages/lint/src/rules/
media.ts`, alongside `audio_volume_double_automation`) warns when a
`data-fx-carve`'s `sources` names two or more plain clip ids instead of a
group — the shape that silently rots when a clip is added. `/hyperframes-
audio` states the same rule as an invariant, not a tip, with the grouped-
narration HTML example from the design doc.

The group-matching and auto-group logic (`withAutoGroupedSources`,
`collectCarveCandidates`) is split into `useFxCarveGrouping.ts` —
`useFxCarve.ts` was pushing past the 600-line cap. `resolveNextCarveSettings`
is deliberately NOT an `async function`: wrapping it in one would force a
microtask on every call, including the synchronous branch — the exact bug
`withAutoGroupedSources`'s own sync-when-possible contract exists to avoid,
and one caught via `propertyPanelAudioFxGroup.test.tsx` (10 failures)
before fixing it back to a plain function the caller conditionally awaits.

Also extracted `useEffectiveTimelineDuration` out of `App.tsx` and
`useRemoveBackground` out of `StudioRightPanel.tsx` (both pushed past 600
lines from an added prop wire), and decomposed `useFxCarve.ts`'s picker
IIFE to clear fallow's complexity gate.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

* feat(engine): render grouped audio through a summed, FX-processed bus

Renders what B3 already routes in preview: a group's members sub-mix into
one PCM WAV at full composition length (adelay already places each member
at its composition position, so the group WAV's t=0 IS composition time),
run through the group's own FX chain and automation via the same
applyAudioFxChain/envelope-bake path a member uses, then fold into the flat
track list as one processed AudioTrack — the final mixAudioTracks call
never has to know groups exist.

Gain law verified against plans/spikes/amix-nesting-spike.sh (brought over
from the plans branch, along with audioMixer.grouping.test.ts, since both
were committed there and never merged to origin/main — every step branch in
this stack descends from origin/main): the sub-mix's own amix prefers
normalize=0 (nulls exactly against a flat mix), falling back to per-node
compensation by the group's OWN member count only when this ffmpeg build's
amix rejects the option. Carrying any other count into a nested amix node
is the exact +2.499 dB silent failure the spike measured — confirmed by a
manual mutation check (wrong-count compensation landed 3.5 dB hot, exactly
20*log10(3/2) for a 2-member group compensated as 3; reverted after
confirming the level test catches it).

A group element carrying data-hidden drops every member before the sub-mix
ever runs (RULES: mute-by-drop, never mute-by-volume-0) — parseAudioElements
now resolves groups once per parse and skips hidden-group members the same
way it already skips data-hidden ancestors.

HfAudioGroup (packages/core/src/audioGroups.ts, from B1) gains fxChain,
automation, volume and hidden, read off the group element the same way
resolveAudioGroups already reads data-label — audioGroups.test.ts updated
for the wider shape plus new coverage for the added reads.

it.todo("mixes a grouped composition at the same level as the ungrouped
one") is now a real, passing test; two more added per the step doc (FX
routing isolation, member-level envelope survives grouping).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>
2026-08-21 09:42:34 -07:00
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