nx_vdeblock_gate.nx

nx_vdeblock_gate.nx -- proves the wired deblocking pass (nx_vdeblock) reduces BLOCKING artifacts. Build a smooth gradient (the true signal), then a "blocky" version that quantizes each 4x4 block to its block mean (the DC-step artifact quantization leaves at block edges). Deblock the blocky frame and MEASURE that it moves back toward the smooth original (higher PSNR, lower block-edge discontinuity) -- i.e. the filter smooths false block edges.