AURA: An Any-format Unified Representation for Spatial Audio

Spatial audio is produced and consumed in a zoo of mutually incompatible formats—channel-based layouts such as 5.1, 7.1 and 7.1.4, and scene-based Ambisonics (FOA, HOA). Existing systems either hard-wire a single input/output pair (e.g. stereo-to-7.1.4 upmixing) or route everything through a fixed, order-limited Ambisonics basis whose angular resolution is capped a priori. We introduce AURA (an Any-format Unified Representation for spatial Audio), which maps any spatial-audio format into a single learnable, format-agnostic soundfield latent z_field and decodes it back into any target format. The latent is kept physically grounded by two inductive biases: geometry conditioning, which tags every channel with its physical direction via spherical-harmonic features and treats it as an element of an unordered set, making the encoder permutation-invariant and shared across formats of differing channel counts; and an Ambisonics physics prior, which regularizes z_field toward the deterministic HOA encoding of the input so the latent adapts to content without collapsing into an opaque channel code. Two capabilities follow: any-to-any format conversion, by encoding an input and decoding to the desired layout; and stereo-to-soundfield generation, where a flow-matching model generates z_field from stereo and renders it to arbitrary formats with mutually consistent outputs. On real corpora (STARSS22/23, Freesound 5.1, 3D-MARCo), the frozen front-end preserves spatial structure almost losslessly (sub-degree to 1.5° round-trip DOA error), and on the real 5.1 test set AURA reproduces the reference's inter-channel energy structure far more faithfully than a deterministic upmix (44.3 dB dynamic range vs. 91.0 dB, reference 57.9 dB).