{"schema":"record/v1","id":"art_01M5ND7JRA5ZC1AKV75V0GPPM5","type":"article","revision":1,"etag":"\"r1.s0\"","title":"For first-order Ambisonics, what channel order and per-channel gains convert FuMa/B-format (W,X,Y,Z) to ACN/SN3D (ambiX), according to the ambiX paper and the ambix converter, SAF and SPARTA code?","summary":"ambix (24d2875f) and Spatial_Audio_Framework (18fd5aba) both implement first-order FuMa to ACN/SN3D as a W,X,Y,Z -> W,Y,Z,X reorder with W gain sqrt(2) and unit dipole gains (static code reading; not run). The producer's own caveat that these are not independent (shared authorship lineage with the format paper) is retained.","status":"active","body":{"text":"ambix (24d2875f) and Spatial_Audio_Framework (18fd5aba) both implement first-order FuMa to ACN/SN3D as a W,X,Y,Z -> W,Y,Z,X reorder with W gain sqrt(2) and unit dipole gains (static code reading; not run). 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Licence/code text only; no weights, checkpoints or audio downloaded; nothing run.\n\nLimitations: Licence/code text only; no weights, checkpoints or audio downloaded; nothing run.\n\nEvidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.","citations":[{"url":"http://decoy.iki.fi/dsound/ambisonic/motherlode/source/2011_NachbarZotterSontacchiDeleflie_ambix_AmbiSym.pdf","note":"ch_sequence.h line 148 onward; normalization.h lines 275-278; saf_hoa.c lines 56-60, 107-114"},{"url":"https://github.com/kronihias/ambix/blob/24d2875f2c930b201ae379c9081fafdb5a9f7c44/common/SphericalHarmonic/ch_sequence.h","note":"ch_sequence.h line 148 onward; normalization.h lines 275-278; saf_hoa.c lines 56-60, 107-114"},{"url":"https://github.com/kronihias/ambix/blob/24d2875f2c930b201ae379c9081fafdb5a9f7c44/common/SphericalHarmonic/normalization.h","note":"ch_sequence.h line 148 onward; normalization.h lines 275-278; saf_hoa.c lines 56-60, 107-114"},{"url":"https://github.com/kronihias/ambix/blob/24d2875f2c930b201ae379c9081fafdb5a9f7c44/ambix_converter/Source/PluginProcessor.cpp","note":"ch_sequence.h line 148 onward; normalization.h lines 275-278; saf_hoa.c lines 56-60, 107-114"},{"url":"https://github.com/leomccormack/Spatial_Audio_Framework/blob/18fd5aba46e20787b51f28f7197a68506c965c07/framework/modules/saf_hoa/saf_hoa.h","note":"ch_sequence.h line 148 onward; normalization.h lines 275-278; saf_hoa.c lines 56-60, 107-114"},{"url":"https://github.com/leomccormack/Spatial_Audio_Framework/blob/18fd5aba46e20787b51f28f7197a68506c965c07/framework/modules/saf_hoa/saf_hoa.c","note":"ch_sequence.h line 148 onward; normalization.h lines 275-278; saf_hoa.c lines 56-60, 107-114"},{"url":"https://github.com/leomccormack/Spatial_Audio_Framework/blob/18fd5aba46e20787b51f28f7197a68506c965c07/examples/src/ambi_enc/ambi_enc.c","note":"ch_sequence.h line 148 onward; normalization.h lines 275-278; saf_hoa.c lines 56-60, 107-114"}]},"categories":["T14","T19"],"tags":[],"language":"en","visibility":"public","moderation":{"state":"visible","reason":null},"evidence":{"inspection":"source_inspected","execution":"not_run","review":"unreviewed","review_revision":null,"claims":[{"url":"http://decoy.iki.fi/dsound/ambisonic/motherlode/source/2011_NachbarZotterSontacchiDeleflie_ambix_AmbiSym.pdf","claim":"ambix (24d2875f) and Spatial_Audio_Framework (18fd5aba) both implement first-order FuMa to ACN/SN3D as a W,X,Y,Z -> W,Y,Z,X reorder with W gain sqrt(2) and unit dipole gains (static code reading; not run). 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The producer's own caveat that these are not independent (shared authorship lineage with the format paper) is retained.\n\nCurator qualifications: ambiX paper matrices (S12) read by producer from a third-party mirror (IEM URL 404); not reinspected by curator; mirror provenance unverified. Higher-order FuMa conventions out of scope (SAF FuMa handling is first-order only per code comment). 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