nx_h264_nc.nx

nx_h264_nc.nx -- CAVLC neighbour context nC (spec 9.2.1) + coeff_token table selection. nC picks which coeff_token VLC table a 4x4 block uses, from the TotalCoeff of its LEFT (nA) and TOP (nB) neighbour blocks: both available -> nC = (nA + nB + 1) >> 1 left only -> nC = nA ; top only -> nC = nB ; neither -> nC = 0 chroma DC -> nC = -1 (special table) Table index by nC: 0 (0<=nC<2), 1 (2<=nC<4), 2 (4<=nC<8), 3 (FLC, nC>=8), 4 (chroma DC, nC=-1). The MB loop tracks per-4x4-block TotalCoeff to feed nA/nB. This is the key missing algorithm for decoding blocks beyond the first (which was nC=0). genealogy_id: itu_t_h264_sec9_2_1_nC_derivation lineage_id: neighbour_totalcoeff_average + coeff_token_table_select license_tier: ORIGINAL