AudioClip -> WAV/OGG (FSB5 + Vorbis) #48

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1. fatal10110

   added this to the M6+ - Backlog (on demand) milestone on Sep 21, 2026
2. fatal10110

   added

   backlogOn-demand, no named consumer yetOn-demand, no named consumer yet

   on Sep 21, 2026
3. fatal10110

   added a parent issue on Sep 21, 2026

   • [M6+] Epic: backlog (on-demand features) #46
4. fatal10110 commented on Oct 6, 2026

   

   fatal10110

   on Oct 6, 2026 – with Claude

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   Research notes (2026-10-06): FSB5 → OGG/WAV needs no WASM

   The libogg + libvorbis WASM package in this issue's body is not needed for OGG export.

   Fmod5Sharp (C#, MIT) rebuilds FSB5 Vorbis without libvorbis and without any audio maths (FmodVorbisRebuilder.cs):

   • The Vorbis setup header that FSB5 strips is looked up by the CRC32 in the VORBISDATA chunk, in a precomputed table (embedded resource vorbis_headers_converted.json).
   • The rest is repackaging: it builds the info, comment and setup packets, wraps the existing compressed frames in Ogg pages, and recalculates granule positions. OggVorbisEncoder is used only for Ogg container writing, never for encoding.
   • It also decodes PCM8/16/32, GCADPCM, IMAADPCM and FADPCM in managed code. MPEG, CELT, AT9, Opus, XMA and PCMFLOAT are not supported there.

   Proposed approach

   • Hand-port the logic to TS, with the C# read-only and cloned outside the repo (R2), in its own package unity-asset-reader-audio. It is pure TS and sync, so D4 holds.
   • Use python-fsb5 (MIT) as the second reference.
   • Writing the Ogg pages (page header + Ogg CRC32) is about 100–200 lines of TS; no Ogg library is needed.

   Open question before porting

   Where does the setup-header table come from, and under what licence? It appears to be extracted from FMOD, which is proprietary, and is presumably the same table python-fsb5 ships. Neither point is verified.

   • If the table cannot be shipped, the fallback is generating setup headers from the stream parameters. That pulls in Vorbis encoder logic and makes the port much larger.

   Oracle

   There is no FMOD-free oracle. AssetStudio uses the FMOD Studio API, and UnityPy's export/AudioClipConverter.py calls fmod_toolkit.raw_to_wav.

   • Expected output could come from Fmod5Sharp or python-fsb5 run outside the repo, with the verdict recorded per plan §6. Comparing WAV after decoding is another option.
   • For OGG output, an independent check is that the result is a valid Ogg Vorbis stream whose decoded PCM is close to the source tone.wav.

   Optional: decoding Vorbis to PCM

   • Not needed for OGG export.
   • If ever wanted: @wasm-audio-decoders/ogg-vorbis (MIT, prebuilt libvorbis, ~99 KiB minified), or the browser's decodeAudioData, which is async and so stays outside the parse path per D4.

   Fixtures

   Already committed: the audio bundles of fixtures/BUILDING.md §11 (2019.4.41f2, 2020.3.30f1, 6000.3.25f1) hold tone-pcm (PCM) and tone-vorbis (Vorbis) as FSB5 in the .resource node.

   Rough size

   About 2 PRs (FSB5 parser + PCM/ADPCM → WAV; Vorbis → OGG), roughly 1–1.5M agent tokens with the usual review loop. This assumes the header-table question is settled first.

   ---

   Generated by Claude Code
5. fatal10110

   added sub-issues on Oct 16, 2026

   • Audio package: FSB5 parser, PCM/ADPCM to WAV #236
   • Audio package: FSB5 Vorbis to Ogg #241
   • Audio: IMAADPCM fixture clips (mono, stereo) with AssetStudio WAV goldens #251