nx_vcodec_mvbits_probe.nx

nx_vcodec_mvbits_probe.nx -- MEASURE the MV-coding overhead (handoff doctrine: sensor before build). Our MV syntax is ve_vput = flat [5-bit length][payload] per component + 4 qpel bits, coded ABSOLUTE (no prediction). x264 codes MV DELTAS vs the median of {left, top, top-right} neighbours -- near-zero deltas on smooth motion fields. This probe runs the REAL encoder (emode 4005, recon-chained, key+11P like arm_p) and, per coded MB, re-derives the same skip gate + integer/qpel-free MV the coder finds, tallying: (a) actual ve_vput bits, (b) bits if coded as delta-vs-median with the SAME VLC, (c) delta-vs-median with an exp-golomb VLC (the H.264-class mvd code). Against the frame's REAL total bytes -> MV share % and the measured prize of median prediction. Approximation: 16x16-level only (partition sub-MVs ignored -> UNDER-counts, conservative). license_tier: ORIGINAL