Binaural and SOFA

--binaural renders an OpenJOC speaker field to two-channel headphone output. It is virtual-speaker rendering; it is not a direct-object or proprietary renderer-fidelity claim.

openjoc render-joc input.m4a \\
  --binaural \\
  --output headphones.wav

The default virtual layout is 7.1.4. The bundled offline SADIE II D1 HRTF is used when no SOFA path is supplied. A custom dataset selects the supported local SOFA path:

openjoc render-joc input.m4a \\
  --binaural \\
  --binaural-sofa listener.sofa \\
  --backend direct \\
  --output custom-headphones.wav

--virtual-layout 9.1.6 selects the canonical experimental 16-channel virtual layout (FL, FR, FC, LFE, Lb, Rb, Ls, Rs, Lw, Rw, Ltf, Rtf, Ltm, Rtm, Ltr, Rtr). The virtual feeds still pass through the same SOFA/HRTF backend and the final output remains two-channel binaural PCM. The default remains 7.1.4; 9.1.6 is not a claim of perceptual superiority.

SOFA scope

The loader accepts the documented SimpleFreeFieldHRIR NetCDF classic CDF-1 subset. The file must provide two receivers, the matching sample rate, and exact or safely interpolatable coverage for every requested non-LFE virtual direction. HDF5/NetCDF-4, resampling, downloads, writing, moving sources, and universal coverage are not supported.

Inspect a file before using it:

openjoc sofa inspect listener.sofa --json

direct is the numerical reference backend. partitioned uses one fixed power-of-two partition size and preserves the complete input and FIR tail. Both backends fail closed on unsupported coverage or sample-rate mismatch.

LFE policy

The CLI defaults to exclude. Use equal-power-dual-mono when you explicitly want the logical LFE contribution sent to both ears:

openjoc render-joc input.m4a \\
  --binaural \\
  --lfe-policy equal-power-dual-mono \\
  --output headphones-with-lfe.wav

The choice is a renderer policy. It does not infer a physical subwoofer or alter the source scene.