acdream/docs/plans/2026-08-08-audio-parity-campaign.md

# Campaign A — Audio retail-feel parity

**Status: PROPOSED 2026-08-08 — awaiting user go.** Research phase complete;
six-lane named-retail decode done, all load-bearing claims byte-verified
against the PDB-paired 2013 binary (BN pseudo-C alone was NOT sufficient —
see "BN traps" below).

**Goal:** the client sounds like retail. Every divergence between our audio
runtime and the 2013 EoR client is either fixed to the retail mechanism or
recorded in the divergence register with a reason.

**Research base (read the lane note before implementing its slice):**

| Lane | Note | Owns |
|---|---|---|
| 1 | `docs/research/2026-08-08-audio-retail-soundmanager-core.md` | SoundManager, falloff, pan, voice pool, prefs |
| 2 | `docs/research/2026-08-08-audio-retail-ambient-runtime.md` | AmbientSound/ConstantSound/IntermitSound runtime |
| 3 | `docs/research/2026-08-08-audio-retail-ambient-authoring.md` | Region-file authoring chain, dat coverage |
| 4 | `docs/research/2026-08-08-audio-retail-dat-layer.md` | SoundTable/Wave formats, selection model, dat census |
| 5 | `docs/research/2026-08-08-audio-retail-server-sounds.md` | 0xF750 wire path, play_sound, trigger catalog |
| 6 | `docs/research/2026-08-08-audio-retail-music-absence.md` | Music (there is none), MediaMachine, AdminEnvirons |

The older `docs/research/deepdives/r05-audio-sound.md` is SUPERSEDED where it
conflicts with the lane notes (its §5.1 falloff, §6 music, and §7 ambient
sections are wrong — Ghidra-era `FUN_xxx` reads that the named decomp + byte
decode overturned). Slice A6 adds the banner.

---

## What retail's audio engine actually is (one page)

Retail is a **2D pan+gain engine**, not 3D audio. Every gameplay buffer is
created with `m_3D = 0`; the DirectSound 3D listener the client sets up is
dead code. Spatialization is CPU-side per voice at play time:

- **Gain** (`SoundManager::GetAttenuation @ 0x00550020`; byte-decoded):
  `g = dist < 5m ? vol : 25·vol/dist²`, clamped to 1.0, then multiplied by ONE
  master knob (`effect_sound_volume` or `ambient_sound_volume`) — clamp
  first, multiply second — then `db = ceil(20·log10 g)` with a hard floor at
  −50 dB, below which the voice is **not allocated at all**. Audible radius
  ≈ 94.2 m at vol 1.0.
- **Pan**: `pan_dB = (int)(−15·sin(Δbearing))`, truncating toward zero,
  saturated at ±15 dB, forced to 0 when `(int)distance < 5`. No front/back,
  no elevation.
- **Listener** = `SmartBox::viewer` — the **collided third-person camera**
  Position, refreshed once per rendered frame (`SmartBox::set_viewer` @
  `0x00452D36`, `SmartBox::update_viewer` @ `0x00453CE0`), falling back to the
  player's own position when the camera sweep fails. Only its origin and
  `Frame::get_heading` are read. (An earlier draft of this plan said the
  listener is the player and called acdream's camera listener a defect —
  wrong, and corrected at A2. Do not re-"fix" it.)
- **Voice pool**: allocator is `SoundManager::PlaySoundInternal @ 0x0054FEC0`.
  Eviction compares the DAT-authored **float priority** (0..1); equal
  priority never evicts. (`FUN_00550AD0` cited in our code is a hash-table
  constructor — wrong symbol.)
- **No loops, no pitch**: retail never sets the DSound loop flag and never
  calls `SetFrequency`. "Looping" ambients are re-fired one-shots.
- **Variant selection** (`SoundTableData::Lookup` + play sites): pick
  `idx = (int)(roll01 · (n−1))` — uniform over all but the LAST entry
  (a genuine Turbine off-by-one; the last variant is unreachable and a
  faithful port keeps that) — then a SEPARATE Bernoulli gate
  `rand()/32767 < probability`, else **silence**. Probability is a gate,
  not a weight.
- **Volume field** is unbounded gain (dats go up to 10.0); retail clamps
  only AFTER the distance divide, so >1 volumes extend audible range.
- **Prefs** (`InitPrefs @ 0x005503F0`, 8 keys): three float volumes
  (effect / ambient / interface — interface is registered but **never
  read**), three enable bools, `Sound Features` (==1 disables pan),
  `Play Sound Only When Active`. There is NO music knob.
- **Quirk (faithful-port decision)**: effect and ambient volumes are each
  applied twice (once at the play site, again inside GetAttenuation) — the
  sliders are effectively **squared**.

**Sound triggers, exhaustively** (lane 5): (1) animation hooks
(SoundHook/SoundTableHook/SoundTweakedHook) — footsteps, combat swooshes,
all authored in MotionTables; (2) the server `Sound` event **0xF750**
(`guid, SoundType, vol`) — hits, wounds, wield, pickup, locks, lifestone,
spell resists; retail queues an event for a not-yet-known guid and replays
it on CreateObject, and plays at the WIRE volume, ignoring the table
entry's volume (the hook path does the opposite); (3) PhysicsScripts
(0xF754/5 — already live in acdream); (4) UI sounds via the ClientUISystem
sound table loaded by `DBObj::GetByEnum(0x22, slot 7)`; (5) region-authored
ambients (below). `CPhysicsObj::play_sound` has exactly ONE caller — the
0xF750 handler. There are NO client-local collision/jump/water sound call
sites; inventing one is a divergence.

**Ambients** (lanes 2+3): authored entirely in `region.dat`
(`Region.SoundInfo` → `AmbientSTBDesc[]` referenced by scene types ← terrain
types). On every **objcell change** (24 m), `CellManager::ChangePosition`
rebuilds weights by walking the **3×3 landblock ring × 64 land cells each**,
decoding each cell's terrain word to (terrainType, sceneIdx) and
accumulating per-sound inverse-square weight (1.0 inside 20 m, `(20/d)²` to
120 m, 0 beyond) plus an 8-way bearing histogram. Playback is a min-heap of
absolute deadlines ticked from the frame loop; each pop plays a one-shot
and re-arms. `base_chance == 0` ⇒ **ConstantSound**: non-positional,
volume = its weight share of total (a real terrain crossfade), re-fires
every `min_rate` s. Non-zero ⇒ **IntermitSound**: authored fixed volume,
positioned at a random accumulated bearing ±11.25° at distance
`min + (max−min)·t²`, gated by `roll ≤ base_chance`, interval
`RollDice(min_rate, max_rate)`. **Indoors is silent by design** —
`CEnvCell::add_ambient_sounds` is an empty folded `ret`; EnvCell has no
sound data. No day/night/weather selection exists.

**Music does not exist** (lane 6): the linked winmm MIDI player has zero
callers (`midiPlay` = 4 textual occurrences: definition + its own queue
drainer; verified independently), "music" appears 0 times in the 65 MB
decomp, no SoundType music member, no music pref, no music files shipped.
`MediaMachine` is a UI-state media bytecode VM whose `Update_Sound` routes
LayoutDesc-authored waves/table rows to the interface bus.

### BN traps (binding on every slice — reread before porting)

Binary Ninja renders x87 memory-operand compares as unimplemented `bool p`
and elides the constants; **five** sites would have ported with inverted
polarity or zeroed math: `is_continuous`, both `CanHear`s, `PlayNow`,
`PlayProbability`, plus `GetAttenuation` printing `* 0f`. Byte-decode the
PDB-paired binary (`reference_pe_byte_decode.md` workflow) for ANY float
compare or constant in this subsystem. The lane notes contain the verified
values; if a needed constant is not in a note, decode it — do not trust
the pseudo-C rendering and do not guess.

---

## Where acdream is today

Working and retail-correct-in-shape: the animation-hook trigger path
(`AudioHookSink`, correctly the only client-local trigger), SoundTable/Wave
dat parsing (byte-exact vs retail), `SoundId` enum (golden-conformance
tested), entity→SoundTable resolution (Setup-then-wire precedence),
world-audio quiescence across portal transitions, AL buffer budget/lifetime.

Divergent or missing, ranked by audible impact:

| # | Defect | Where | Symptom |
|---|---|---|---|
| 1 | Probability gate absent: `SoundCookbook.Roll` short-circuits single-entry lists (4,183/4,184 entries!) before any roll; CDF walk instead of `(n−1)` pick + gate | `SoundCookbook.cs` | Idle chatter ~20× too often; nothing ever randomly silent — the "incorrect ambient-ish noise" complaint |
| 2 | 0xF750 unhandled — zero hits in `src/` | `Core.Net` routing | Every server cue silent (hits, wounds, pickup, locks, lifestone…) |
| 3 | Falloff: AL `InverseDistanceClamped` ref 2 m ⇒ `2/d` first-power, no −50 dB cutoff; AL's 3D panner instead of retail's ±15 dB angular pan | engine + `WorldRenderFrameBuilder` | Wrong loudness curve in both directions — quieter than retail up close, audible where retail is silent; stereo image wider and 3-D where retail's is a narrow angular pan (AP-28) |
| 4 | Priority float [0,1] cast to int 0..7 → 4,100 entries collapse to 0; eviction compares gain not priority | `AudioModel`/engine | Eviction ordering gutted under voice pressure |
| 5 | Volume clamped at field instead of after distance divide | `AudioHookSink` | >1-gain sounds lose up to 3× audible range |
| 6 | Region ambient system absent (`StartAmbient` stub) | engine | Silent outdoors atmosphere (TS-29 half) |
| 7 | UI sound bank absent; AdminEnvirons stingers logged not played; portal enter/exit cues missing | — | TS-54, AP-115 |
| 8 | `PlayMusic`/`StopMusic`/`MusicVolume` model retail code that never runs | `IAudioEngine`, settings | Dead API + misleading settings knob |
| 9 | Dead code: `AudioFalloff` (wrong constants, unused), wrong `FUN_00550ad0` citation, invented `PitchMin/PitchMax`+`Loop`+`Is3D` fields on `SoundEntry` | `AudioModel.cs`, engine header | Traps for future readers |

Register rows in scope: **AP-28** (retire at A2), **AP-115** sound half
(retire at A4), **TS-29** (retire at A5/A6), **TS-54** (retire at A4),
**TS-9** (re-scope at A6 — dat census says exactly 1 of 786 waves is MP3).
Issue **#321** (sound-cache decode-dedup race) folds into A6.

---

## Slices

Ordering is audible-value per effort; A1–A2 are the "it sounds wrong"
fixes, A3–A4 the "it's silent where retail speaks" fixes, A5 the big new
system, A6 the cleanup. Each slice: grep-named → (byte-decode if any new
constant) → pseudocode check against lane note → port → conformance tests →
build/test green → commit; user listening gates where marked.

### A1 — Selection-model correctness (small; biggest audible fix)

Replace `SoundCookbook.Roll` with retail's exact model: uniform
`idx = (int)(roll01 · (n−1))` (preserving the last-entry-unreachable
off-by-one), then the separate Bernoulli probability gate returning
"silence" — including for single-entry lists. Priority stays float [0,1]
end-to-end (`SoundEntry.Priority`, engine slots). Volume passes through
unclamped; clamp moves to post-attenuation (staged here, consumed by A2).
Delete the invented `PitchMin/PitchMax/Loop/Is3D` fields. Rewrite
`SoundCookbookTests` against golden values from the lane-4 note's decoded
tables; add a distribution test for the gate.

Acceptance: conformance tests green; connected sanity — creature idle
chatter audibly rare (Speak1 ≈ 5% per trigger, was 100%).

### A2 — Falloff/pan/listener/voice parity (retires AP-28)

Port `GetAttenuation` + pan CPU-side exactly (5 m knee, `25·vol/d²`,
clamp-after, ceil-dB, −50 dB no-allocate floor, `−15·sin(Δheading)` pan
±15 dB with 5 m dead zone, `Sound Features==1` pan disable). OpenAL
becomes a dumb 2D voice bank: source-relative sources, per-voice gain +
pan (AL_POSITION azimuth from pan only); remove AL's distance model and the
listener orientation math.

**Listener correction (2026-08-08, from the lane-1 decode):** an earlier draft
of this plan said the listener must move "from camera pose to player
position/heading" and listed "listener = CAMERA" as a defect. That was wrong,
and it was written before lane 1 landed. Retail's listener IS the camera:
`SmartBox::set_viewer` @ `0x00452D36` hands the same COLLIDED third-person
camera Position to `SoundManager::SetPlayerPosition`, the sky, and the camera
setup, refreshed once per rendered frame from `SmartBox::update_viewer` @
`0x00453CE0` (falling back to the player's own position when the sphere sweep
fails). acdream's chase camera collides too, so the position source was already
faithful; only the HEADING extraction changes, since retail reads
`Frame::get_heading` — one compass bearing — and never a forward/up basis.
Do not "fix" this back.

Eviction compares float priority (equal never
evicts); fix the pool citation to `PlaySoundInternal @ 0x0054FEC0`.
Keep the squared-volume quirk faithful (register row if we later soften
it). Map settings: Master (ours, AL listener gain) + Effect + Ambient +
Interface mirroring retail's knobs; note interface is read by no retail
path (we wire it to the UI bus anyway — divergence row, deliberate).

Acceptance: unit tests on gain/pan tables (golden distances from lane 1
note); **user listening gate** — side-by-side with retail: walk away from
a blacksmith's hammering, confirm matching fade-out distance (~94 m) and
pan behavior.

### A3 — Server sound path (0xF750)

Parse `Sound` (guid, SoundType u32, volume f32) in the message router;
route to a new `ServerSoundController`: resolve guid → entity; unknown
guid ⇒ queue the event and replay on CreateObject (retail
`CObjectMaint` behavior); known guid without SoundTable ⇒ silent drop;
play via the SoundTable at the **wire volume** (ignore table volume —
asymmetric with the hook path, byte-verified). Position at the entity's
current origin.

Acceptance: wire-format conformance test (three-oracle layout);
connected gate — melee hits, item pickup/drop, lifestone bind audibly
fire against ACE.

### A4 — UI + interface sounds (retires TS-54, AP-115's sound half)

Load the ClientUISystem sound table (`GetByEnum` cache 0x22, enum slot 7 —
resolve the actual DID at port time from `ClientUISystem::GetUISoundTable`).
Route `PlayUi(SoundId)` through it (delete the no-op). Wire:
AdminEnvirons 0x65..0x7C → `PlaySoundFromCenter` stingers
(`WorldEnvironmentController.ApplyAdminEnvirons` already parses them);
portal enter/exit `UI_EnterPortal`/`UI_ExitPortal`; button/panel cues where
the retained UI already has command seams; `MediaDescSound` support in
`LayoutImporter` (DatReaderWriter parses it; interface bus, per lane 6).

Acceptance: connected gate — `@environs` thunder/drums audible; portal
enter/exit cues audible on recall; **user listening gate** vs retail.

### A5 — Region ambient system (retires TS-29's ambient half)

New `AmbientSoundSystem` (App layer, owned like other world controllers):
rebuild on objcell change (reuse streaming's cell-transit signal), walk
the 3×3 ring × 64 cells via the SAME terrain-word decode the scenery
pipeline uses (`SceneryGenerator`-shared helper), accumulate weight
(1.0 ≤ 20 m, `(20/d)²` ≤ 120 m) + 8-way bearing, build
Constant/Intermit instances from `AmbientSTBDesc` (`base_chance == 0` ⇒
constant — the byte-verified polarity), min-heap of absolute deadlines
ticked per frame, one-shots through the ambient volume path (squared,
faithful). ConstantSound non-positional; IntermitSound positioned at
random accumulated bearing, `min + (max−min)·t²` distance. Teardown on
world transition via the existing quiescence edge. Indoors: NO ambients
(retail-faithful); `seen_outside` cells get the outdoor set. Delete
`StartAmbient`/`StopAmbient` from `IAudioEngine` (wrong shape — looping
handle API models a mechanism retail doesn't have).

Acceptance: unit tests on weight accumulation + scheduler with a synthetic
region; **user listening gate** — Holtburg outdoors vs retail side-by-side
(birdsong/wind character and rough cadence), dungeon silence, ambient
crossfade walking shore → grass.

### A6 — Deletions, bookkeeping, and the long tail

- Delete `PlayMusic`/`StopMusic`/`MusicVolume` and the `AudioSettings.Music`
  knob (settings migration: drop the field, tolerate old json). Retail has
  no music system; register row NOT needed once the API is gone (nothing
  diverges — absence matches retail).
- Delete dead `AudioFalloff` (superseded by A2's ported math).
- r05 doc: SUPERSEDED banner pointing at the six lane notes; corrections
  list from lane notes §12/§13.
- TS-9 re-scope: 1 MP3 wave in the shipped dats (`0x0A000393`, ~2 s) —
  either a ~50-line managed MP3 decode for one asset or an accepted-loss
  row with the census cited. ADPCM count to be measured the same way
  before deciding.
- #321: make `DatSoundCache` decode-dedup safe under concurrent access
  (single-flight per wave id) — the full-suite flake.
- Register sweep: retire AP-28/TS-29/TS-54 rows in their landing slices'
  commits (rule 1); add rows for: interface-volume wired (A2), any
  softened quirk, and anything discovered mid-campaign.

Acceptance: build/test green, register diff reviewed, no orphaned
API/settings references.

---

## Out of scope (explicitly)

- Client-local physics sounds (collision/jump/water) — retail has none;
  the server sends them. Do not invent.
- Indoor ambient beds — retail is silent indoors.
- A music system — retail has none. (If we ever WANT music, that's a
  new-feature decision for the user, not parity work.)
- HRTF/doppler/reverb — no retail counterpart.

## Rollback

Each slice is one commit (A6 possibly two); rollback is `git revert
<slice-sha>`, recorded in this doc's ledger as slices land. A2 and A5 are
the only slices touching frame-loop code paths; both are behind the
existing audio-availability guard, so `ACDREAM_NO_AUDIO=1` remains the
global kill switch.

## Ledger

| Slice | Status | Commit | Gates |
|---|---|---|---|
| A1 | **COMPLETE** 2026-08-08 | `c69b3bde` | 42 Core audio tests; full Release suite 11,563 passed / 4 skipped / 0 failed. Closes #355. |
| A2 | **COMPLETE** 2026-08-08 | `6d0156cb` | 118 Core audio tests (mixer + voice pool + cookbook); full Release suite 11,639 passed / 4 skipped / 0 failed. Opus review run and applied — 2 HIGH (pan-law saturation, stale `FUN_00550ad0` header), 5 MEDIUM (untested clamp order / pan truncation / voice pool, dead `PlayingGain`, duplicated heading helper), 5 LOW. Retires AP-28; files AP-173, AP-174, TS-64, TS-65. **Owed: user listening gate.** |
| A3 | **COMPLETE** 2026-08-08 | `3fae0c7d` | 14 wire-conformance tests + 5 controller tests; full Release suite 11,658 passed / 4 skipped / 0 failed. **Owed: connected gate** (melee hit / pickup / lifestone audible against ACE). |
| A4 | **COMPLETE** 2026-08-08 | `489ea6ad` | UI bank DID resolved from the dats (`0x2000004B`, content-verified: exactly the 32 `UI_*` slots) + 21-case environ table, 30 new Core tests; full Release suite 11,691 passed / 4 skipped. Retires TS-54; narrows AP-115 to notice-only. **Owed: connected gate** (`@environs` thunder + recall cues audible). **Suite note:** two load-dependent measurement flakes were observed on separate full-suite runs (`RuntimeCollisionReportingStateTests.WarmedSteadyContactRefreshDoesNotAllocate`, and one unnamed Core.Net test); both pass in isolation and neither touches audio. |
| A5 | — | — | — |
| A6 | — | — | — |