nx_ringdown_lib.nx

nx_ringdown_lib.nx -- ONE damped-oscillator identifier for the whole estate. WHY THIS EXISTS. The estate has to answer "what is this thing's natural frequency and damping" about TWO subjects that must be comparable: our own XPBD plant (via nx_dyna_bind_skin's ringdown) and REAL FOOTAGE (via nx_dynaoracle's optical-flow displacement series). If each carried its own estimator the comparison would be measuring two rulers, not one subject. Extracted VERBATIM from nx_dyna_bind_skin.dbs_ringdown_t 2026-08-25 so the two cannot disagree BY CONSTRUCTION -- the law the jobclaim lane already paid for. SUBJECT-AGNOSTIC BY DESIGN: it takes a signal, a sample period and a deadband. It knows nothing about tissue, cages, pixels or cameras. Hair, cloth, camera shake and any damped oscillator are the same arithmetic. DOCUMENTED IMPRECISION (carried over, deliberately not silently improved): rd_log2_q16 is a bit-length plus LINEAR mantissa term, worst error about 0.086 in log2 inside an octave. The analyser therefore ALWAYS returns the two raw peak amplitudes beside the derived zeta so any reader can recompute the decrement exactly and is never forced to trust this routine. license_tier: ORIGINAL