.sbao — Sound Binary Audio Object

Verified via direct binary analysis and reverse engineering

The Ogg-backed layout is derived from direct byte-analysis of 54 real music .sbao files (from sound_english.dat), cross-checked against the community workflow in the FarCry2Crew Steam guide. Tooling lives in tools/sbao/sbao_tool.py. The short-SFX codec is identified via GhidraMCP against Dunia.dll — full writeup on the .spk page, since it's the same underlying DARE data reached through a different container path.

.sbao = "sound binary audio object," a standalone (non-bank) DARE resource file — the same "atomic"/"streamed" object model documented on .spk, saved to its own file (<id:08x>.sbao or .bao) instead of packed into a bank. Two layouts exist.

Long audio (music, dialogue): [40-byte header][verbatim Ogg Vorbis bitstream]

An Ogg Vorbis stream in a thin wrapper. The header is byte-identical across every music file except a 16-byte field at 0x08:

Offset	Size	Value (retail)	Meaning
0x00	4	02 1F 00 10	constant type/magic marker — the same one .spk records use
0x04	4 (u32 LE)	28 00 00 00 = 40	offset to the Ogg payload (= header length)
0x08	16	varies per file	asset GUID — not a content hash (verified: ≠ MD5 of payload/whole-file/first-page)
0x18	8	zero	—
0x20	4	00 00 00 50	constant (unidentified; possibly a flags/type field)
0x24	4	02 00 00 00 = 2	constant here (channel count / stereo)

The Ogg payload is a complete, standard Ogg Vorbis bitstream — first page carries the Vorbis identification header, last page has the EOS flag set. Nothing about the audio (length, sample rate, sample count) is duplicated in the wrapper; it all lives in the Vorbis stream itself.

Consequences for modding:

• Decode = carve bytes [40:] to a .ogg.
• Encode/replace = original_header[:40] + new_ogg. No size field, no rate field, and no checksum to recompute — reusing the original 40-byte header (GUID included) is safe because the GUID isn't derived from the content.
• A robust reader should still read the offset at 0x04 rather than hardcode 40 (all retail files use 40, but the field exists for a reason).

The one real constraint: replacement audio must be 48000 Hz stereo. Every retail music file's embedded Vorbis header is 48000 Hz, 2 channels — FC2 plays music at 48 kHz, so a replacement Ogg at a different rate plays at the wrong speed. This is the actual explanation for the Steam guide's "reduce the track speed by −8.120% (×0.919)" instruction for menu music: 44100 / 48000 = 0.91875. People were exporting 44.1 kHz Ogg from Audacity (playing too fast at 48 kHz) and compensating by pre-slowing the audio. The correct fix is simply to export at 48 kHz — no speed adjustment needed. sbao_tool.py repack refuses a non-48 kHz Ogg for exactly this reason.

Short SFX: IMA-ADPCM

No OggS signature (sample: tools/misc/format-samples/004ae237.sbao, starts 8d 06 08 02 — notably not the 02 1F 00 10 magic the long-audio layout and .spk records share, so this sub-type's outer envelope hasn't been directly confirmed to match .spk's FlatCopy record shape byte-for-byte).

The codec itself is confirmed: standard IMA-ADPCM, the same DARE TImaAdpcm data as .spk's FlatCopy records — found via direct byte-search of Dunia.dll for the canonical IMA-ADPCM tables and verified by decoding real payloads end-to-end into playable audio. Full writeup — table addresses, the two decoder functions, the 28-byte per-stream header layout, and the verification — is on the .spk page.

This is a different, unrelated codec family from Ubisoft's older in-house "Ubi Sound Tools" ADPCM dialects (ubi_v3/v5/v6/interleaved, decodable by the third-party tool Ubitunedec, used in older titles like XIII and Splinter Cell) — confirmed by running Ubitunedec directly against a real short-SFX sample: every structural decoder rejects the file on its own signature check, and the buffer-scan mode finds no recognizable chunk (while correctly finding the OggS chunk in a real long-audio sample, confirming the tool itself works). Genuinely just two unrelated codecs that both happen to be "an ADPCM."

Known file id

004b177b.sbao = English main-menu theme (confirmed: matches the Steam guide's stated id and the user-labelled main_theme_004b177b.sbao). Archive-relative path is soundbinary\004b177b.sbao (consistent with the soundbinary\<hash>.spk entries in the community filelists).

Loose-file override path

Sound objects are requested through the engine's VFS by relative path (observed in modpatcher.log: [VFS] passthrough SoundBinary\...), so a repacked file dropped at Data_Win32\Loose\soundbinary\004b177b.sbao is overridden by ModPatcher's Phase 1 VFS_ResolvePath hook (and, if requested by hash, the Phase 2 ArchiveEntry_FindAndOpen hook) — the identical resolver .spk bank loading uses. See archives.