133 lines
10 KiB
Markdown
133 lines
10 KiB
Markdown
# Soundbanks and in-memory sounds
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Most short sound effects (footsteps, foley, combat, weapons, objects, UI, grunts) are **not in the WADs**: they
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are WEMs stored inside Wwise soundbanks, either loose in `SFX\*.bnk` or embedded in the UE3 packages (`.upk`).
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ackit lists them as the catalog archive `BANK` and writes them (see the end of this page).
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Survey of the installed game (buildid 3718300), 2026-10-09.
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## Inventory
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| where | banks | unique in-memory WEMs |
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| loose `SFX\*.bnk` (Batman/Catwoman footsteps, 32 surfaces each, + `TST_Prep_Media`) | 65 | 1,117 |
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| banks embedded in `.upk` packages (in 1,431 of the 2,648 packages) | 3,340 | 14,802 |
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All of them are in the catalog (archive `BANK`).
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The two sets share 119 media IDs: 15,800 unique media IDs in 95,887 places (bank copies). 396 of them are
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**prefetch heads** of streamed WAD sounds and 49 are **whole copies** of WAD recordings (below), so there are
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**15,355 in-memory sounds**. All copies of a
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media ID are byte-identical except `1C898731` (two variants). The WADs, by comparison, are fully covered: the
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BKPK tables in the packages reference 2,543 WAD entries, all of them in the catalog.
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Embedded WEMs by bank name prefix (a media held by banks of two prefixes counts for both): `Speech` 7,827, `CHR`
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(character foley, combat, bosses) 3,624, `PSO` 737, `WPN` 577, `NPC` 471, `OBJ` 411, `SEQ` 253, `PSA` 203,
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`PX` 195, `MTN` 191, `GUI` 155, `DVC` 100, `GEN` 80, `PHY` 73, `AMB` 61, `SBJ` 50, others < 30. The `Speech_` banks (e.g. `Speech_EMOTE_Batman`, `..._GRUNT`) hold
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speech: efforts, grunts and a few other lines stored once for every language (119 sounds) and **localized
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lines** (about 1,450 per language, see *Localized banks*).
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All WEMs seen are Vorbis (format tag 0xFFFF), the same codec as the WADs: the loose footsteps are mono (4
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stereo); of all 15,355 in-memory sounds 13,982 are mono, 1,196 stereo, 177 have 3-6 channels.
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## Names
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- Media IDs have no names of their own: a sound is named after the Wwise event that plays it (event names
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are in the packages' name and export tables, event ID = FNV-1 of the name), else after its bank.
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- `CookedPCConsole\CookedBanks.txt` lists all 3,345 cooked bank names. Bank ID = FNV-1 32 of the lowercased
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name (the same hash Wwise uses for every name). 3,338 of them are embedded in packages (`Music`, `Music_PDLC`
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also as loose `.bnk` files), 2 are only loose `.bnk` files (`Global`, `Init`); `AMB_OW_A6`, `AMB_OW_C1`,
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`AMB_OW_E1`, `Speech_EMOTE_Thug_Muffled_Stop` and `Speech_GFxUI_ArkhamCityStories` were found nowhere.
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- Loose footstep banks are named in their STID chunk (`CHR_BatmanFootsteps_Concrete_Media`, ...).
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## Bank layout (version 56, Wwise 2011.1)
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Chunks `BKHD` {u32 version 56, u32 bank id, ...}, `DIDX` N x {u32 media id, u32 offset, u32 size} (offsets
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relative to the `DATA` payload, WEMs 16-byte aligned), `DATA`, `HIRC`, `STID` {u32 type, u32 count,
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count x {u32 bank id, u8 len, name}}. `Init` (`50C63A23.bnk`) has `STMG`/`ENVS` instead of media.
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`701C1363.bnk` holds only `BKHD`.
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HIRC Sound object (type 2) payload: u32 object id, u32 plugin id (`0x00040001` = Vorbis), u32 stream type
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(0 = in memory, 1 = streamed, 2 = prefetch), u32 media id, u32 bank id of the media; for in-memory sources
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then u32 offset, u32 size, where offset = `DATA` payload position (from the start of the bank) + DIDX offset
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and size = DIDX size (checked on every in-memory source of the footstep banks and of `BmGame.upk`).
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Source kinds over all bank copies: 115,737 in-memory sources of the bank's own media; 2,233 in-memory sources
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with bank id 0 whose media is not in the same bank (loaded by another bank); 133,075 streamed sources;
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2,101 **prefetch** sources. Every streamed or prefetched media ID is in a BKPK table, i.e. a WAD sound
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(`wad.md`). A prefetch source's media is also in the bank's DIDX: that in-memory copy is the **head** of the
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streamed WEM (its size = the source's size), which the game plays while the rest is read from the WAD. 396
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WAD sounds have such heads (2,101 copies); replacing one of them must rewrite the heads too.
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49 more WAD recordings (9-11 per language: game-over taunts, an encryption-card line, a cutscene line, scripted
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story lines) are
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also stored **whole** in banks: an in-memory source with the WAD recording's own media ID, byte-identical to
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the WAD WEM (84 copies). They are handled like heads: part of the WAD line, written and reverted with it, not
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sounds of their own (`catalog.whole_recordings`). Heads and whole copies together: 445 recordings, 2,185
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copies (`BANK_locations.csv.gz` kind `p`).
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## Localized banks
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Speech banks are localized inside the (language-neutral) packages: one `AkBank` export starts with a language
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list (FStrings `INT FRA ITA DEU ESN`) and then holds one block per language, in that order: the BKPK table(s)
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of the speech WAD entry for that language (`wad.md`) and a complete bank, with the same bank ID in every
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language. ackit gives each bank and each BKPK table the language of its position in that list (an export
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whose block count differs from its language count would be reported; none does). Each in-memory media gets
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the languages of the banks that hold it (`BANK.csv` column `language`): 8,092 sounds are language-neutral,
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1,450-1,456 belong to one voice language, 6 to several (5 shared by INT/FRA/ITA/ESN while DEU has its own, 1
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by INT/FRA/ITA); a media stored in the banks of every language is listed as `''` (the same recording
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everywhere; 167 of these are voice lines, e.g. efforts and radio chatter).
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A catalog shows the neutral sounds plus the loaded language's lines; names are unique per language.
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## Lines: one recording per language
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Implemented in `ackit/lines.py`, checked by `ackit verify --catalog`. A voice line exists once per language,
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and the game ties the recordings together itself:
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- Every WEM of a speech WAD has exactly one row in its own language's BKPK table (media ID, offset, size):
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10,816 of 10,816 in each of the 5 languages, no row without a WEM. 657 media IDs are used by several
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languages (cinematics, emotes, Clayface), each at another position in each language's WAD, so the tables
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are kept per language and never merged.
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- Every recording, streamed, prefetched or in memory, is the source of a Wwise Sound object; Sound objects,
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events, actions and containers have the same IDs in every language, only the media differ. A *line* = the
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recordings that are sources of the same Sound objects: 12,434 lines (WAD and in-memory), each with exactly
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one recording in each of the 5 voice languages (61,485 recordings), no Sound object with two recordings in
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one language. Line identity (`line` column) = the smallest Sound object ID.
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- Prefetched sources count too: the 81 lines with a prefetch head (396 recordings over the 5 languages; mostly
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the game-over taunts) are linked only through them. A WAD recording that a bank also stores whole (49) is
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the same recording (same media ID), so its line is unchanged and the bank copies are written with it.
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- 5 recordings per language are stored twice in that language's WAD (same media ID in two entries, byte-
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identical, e.g. `Speech_STEEL_A1_CH2_Thug_behinddoormuffled` and `DIA_SteelA1Muffled`): the second place
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is a copy of the line (same `line`, keeps its position name) and is written and reverted with it, because
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the game plays whichever place the loaded package's table names.
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- Not every line has its own recording in every language; the game shares some itself: in each voice WAD
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616-651 lines are byte-identical to the INT recording (ITA 651: efforts and emotes 509, cinematics 117,
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boss fights 10, story 8, radio/TV 4, character lines 2), 167 in-memory voice lines are stored once for every
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language (efforts, radio chatter, crowds) and 6 DLC intro lines are one recording shared by INT/FRA/ITA(/ESN).
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So some lines play the English recording in every language: that is the game's own data, which the catalog
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shows as it is.
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- Independent checks (no BKPK involved): every WAD recording is named as a source by a Sound object of a bank
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of its own language (54,055 of 54,055); every stored head or whole copy equals the start of the recording
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its line gives it (2,185 of 2,185); a line's recordings have similar lengths across languages (11,761 of 12,434
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within a factor 1.5; the others are different edits, e.g. a 0.55 s ESN line vs 5.46 s elsewhere).
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## Banks inside packages
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- The packages are LZO-compressed UE3 packages (`upk.md`); ackit decompresses them itself and searches the
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uncompressed data for `BKHD` (banks) and `BKPK` (WAD indexes). (The first survey used Gildor's
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decompress.exe; `ackit/upk.py` gives identical data.)
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- Bank blobs in packages: 41,797 for 3,340 bank IDs. Many banks are copied into several packages (e.g.
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`CHR_CatwomanFoleySuit` 31 times, `CHR_BatmanFoleyBelt` 25). 302 bank IDs occur as several blobs with
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*different* media subsets (often one WEM each, several per package), so a bank's media set is the union
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of all its blobs.
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- Largest: `CHR_RobinFoleyCape` 300 WEMs, `CHR_BatmanFoleyCape` 282, `CHR_Clayface` 263,
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`CHR_NightwingFoley` 242, `CHR_CatwomanFoleySuit` 225, `CHR_MrFreeze` 176, `CHR_Combat` 166.
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## How ackit edits them
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- Catalog archive `BANK` (one row per media ID) + `data/catalog/BANK_locations.csv.gz` (every copy, and the
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heads and whole copies of WAD speech recordings); built by `tools/build_catalog.py`, checked by `ackit verify
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--catalog`.
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- A replacement is written **in place into every copy** (no larger than the smallest copy), so DIDX/HIRC
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offsets and sizes and the package layout never change. Loose banks are patched directly; in packages only
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the touched blocks are re-encoded (`upk.md`). A sound left in one package only would let the game load the
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original from another one.
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- **Each copy is filled exactly**, never zero-padded: every in-memory WEM the game ships ends exactly at its
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slot's end, and the game plays a replacement followed by zero padding there as **silence** (findings 24:
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footsteps replaced that way were silent in game; filled, they play). A smaller replacement is grown to the
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slot size with a label list chunk before `data` (`LIST{adtl, labl}`, the form the game's own WEMs use for
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markers; `ackit/wem.py: fill`), so the encoder leaves at least 26 spare bytes, an even number.
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- Replacing a speech line that has prefetch heads or whole copies rewrites them: a head gets the first bytes
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of the new, zero-padded line (the start of the streamed WEM as the WAD stores it); a whole copy is filled
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like an in-memory sound.
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- Design and revert rules: `docs/decisions.md` (4b). The same WEM rules apply (`wem.md`).
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