nx_h264_idct.nx

nx_h264_idct.nx -- H.264 4x4 inverse integer transform (rung 5-core, built bottom-up). THE deterministic DSP kernel at the base of pixel reconstruction: dequantized transform coefficients -> residual samples. Spec ITU-T H.264 section 8.5.12.2 (residual 4x4): two butterfly passes (rows then columns) then r = (h + 32) >> 6. Reusable regardless of the entropy layer above. Arithmetic right shift (floor, sign-preserving) is REQUIRED on negatives. We implement asr() to shift only non-negative magnitudes, so correctness does NOT depend on whether the language '>>' is arithmetic or logical -- the gate's negative outputs (e.g. -1) prove it. genealogy_id: itu_t_h264_sec8_5_residual_transform + malvar_2003_low_complexity_transform lineage_id: integer_butterfly_2pass + round_shift6 license_tier: ORIGINAL