ACR-HR DMOS calculator

A dependency-light Python script (standard library only) that turns raw per-viewer ACR ratings into both numbers a subjective test can report. From a long- or wide-format CSV of per-subject scores for processed clips and their hidden references, it computes each clip's absolute MOS and its ACR-HR Differential MOS using the ITU-T P.910 formula DV = V(PVS) - V(REF) + 5, applies the optional two-point crushing function (crushed_DV = 7*DV/(2+DV) for DV > 5), and reports MOS, DMOS, the standard devia