1. A method, comprising: obtaining local video content at a perceptual video coder; calculating a feature index for each of one or more features of a video unit of the local video content; directly mapping each feature index to a delta quantization parameter (QP) using a linear fractional model that explicitly establishes a relation between the delta QP and a Human Visual System (HVS) insensitivity index wherein the linear fractional model establishes that the delta QP is equal to: a first constant “c” times (a local strength of the HVS insensitivity index plus a second constant “a”)/(the local strength of the HVS insensitivity index plus a second constant “b”), where a<0, b>0, and c>0; refining a QP of an adaptive quantization by adding each delta QP to the QP; and performing the adaptive quantization on the video unit of the local video content based on the refined QP.