nx_bd_calc.nx

nx_bd_calc.nx -- SOVEREIGN Bjontegaard BD-rate (2026-07-29; retires the bd_*.py lane instruments per the sovereign-no-python law -- python remains ONLY as the cubic ORACLE inside this organ's gate). ESTIMATOR (declared): BD-PWL -- piecewise-LINEAR interpolation of log10(rate) over the overlapping PSNR span, trapezoid-integrated. The classic estimator fits a cubic; on the 4-5 point curves this lane sweeps, PWL is monotone, has no ill-conditioned Vandermonde solve, and its delta vs the cubic oracle is MEASURED and bounded in nx_bd_calc_gate (tolerance derived from measurement, never taste). All math is bits-up sovereign binary64 (nx_f64 add/sub/mul/div/log2/exp/cvt). usage: nx_bd_calc <anchor.pts> <test.pts> each line: "<kbps_milli> <psnr_milli>" (integers; kbps_milli = bytes*5 for 48f@30fps CIF sweeps; the milli scaling cancels: log10(1000x)=log10(x)+3 shifts BOTH curves equally, psnr-milli scales numerator and denominator of the average equally) output: "BD_PWL_PERMILLE=<n>" (test-vs-anchor bits at equal quality; negative = test wins) license: ORIGINAL