Spatial portability

OpenJOC implements its spatial rendering DSP directly rather than delegating object rendering to platform-specific spatial audio engines. Operating-system audio APIs may be used for integration and I/O, but they do not define OpenJOC's spatial rendering result.

One renderer. Same spatial semantics across platforms.

Native 22.2

22.2 is the generic OpenJOC speaker preset for ITU-R BS.2051-3 Sound System H (9+10+3): 24 semantic channels, 22 spatial speakers, and two semantic LFEs. The canonical OpenJOC order is:

FL, FR, FC, LFE1, BL, BR, FLc, FRc, BC, LFE2, SiL, SiR,
TpFL, TpFR, TpFC, TpC, TpBL, TpBR, TpSiL, TpSiR, TpBC,
BtFC, BtFL, BtFR

The public source identifies the Sound System H speakers and their admissible azimuth/elevation ranges in Table 10 of ITU-R BS.2051-3. OpenJOC uses deterministic midpoints of those public ranges for its normalized layout data. Bottom, middle, upper, and top are four layers in the same generic SpatialLayout projector; there is no 22.2-specific renderer.

LFE1 and LFE2 are never spatial projection vertices. The current E-AC-3 input boundary supplies one base LFE plane; for a 22.2 physical output that plane is copied to both explicitly labeled LFE destinations. Objects cannot enter either LFE through point, Region, Extent, Spread, Pair, or ChannelLock projection.

WAV output is 24-channel PCM without a fabricated WAVEFORMATEXTENSIBLE mask, because the standard mask cannot faithfully describe the full 22.2 identity set. The CLI reports this limitation. CAF output carries ordered channel descriptions, using standard CAF labels where available and explicit coordinate descriptions for the remaining 22.2 positions.

Built-in generic binaural

--binaural without --sofa selects the bundled SADIE II D1 KU100 generic resource. OpenJOC also ships a SADIE II D2 KEMAR built-in profile in the API/plugin selectors. These are offline data resources, not external renderers. Built-in v2 assets are decoded directly to the same HrirBank representation used by the existing runtime spherical interpolation, delay-aware causal FIR convolution, and tail-drain path. User --sofa FILE remains an explicit SOFA input and malformed files still fail closed.

License gate: HRTF_REDISTRIBUTION_VERIFIED.

SADIE II D1 and D2 each contain 8,802 measured directions plus 15 exact canonical virtual-speaker aliases. The 56-byte .ojhrtf v2 envelope binds preset ID, payload length, and checksum. Its direct payload stores local XYZ directions, ear ordering, per-ear sample delays, and every tap; it does not contain a SOFA or NetCDF file. The offline HDF5-to-CDF1 intermediate converter is tools/generate-builtin-hrtf.py, followed by the Rust pack-hrtf-asset example. Native rendering needs neither HDF5 nor a runtime network download. The Browser Standard package keeps renderer WASM separate and bundles both D1 and D2. It verifies the selected local asset before use, so both profiles work offline after installation. There is no separate Full offline package or runtime HRTF download.

Reproducibility record for the authorized upstream file used for this bundle:

upstream source: SADIE II Zenodo 10886409
derived CDF1 intermediate: preserved hashes in docs/hrtf.md
final format: OJHRTF v2 direct records; SHA-256 pinned in BuiltinHrtf registry
format regeneration: generate-builtin-hrtf.py + pack-hrtf-asset example

The standard default virtual layout is 7.1.4. The resource is native 48 kHz, so no built-in-only resampler is introduced. HRIR delays are zero in this source; the renderer nevertheless preserves its general delay-aware SOFA contract.

API behavior

Rust callers use BinauralConfig::builtin_generic(...) for the default or BinauralConfig::from_sofa_bytes(...) for an explicit user dataset. Existing BinauralConfig { sofa_bytes: ... } construction remains valid: empty bytes select the built-in resource and non-empty bytes select the user SOFA. C ABI callers pass a null/zero SOFA buffer for the built-in resource and a non-empty buffer for a user SOFA; the ABI struct layout and size-compatibility rules are unchanged.