Fast Opto-electrical Transformation of HDR Videos based on a LUT for Piecewise Linear Approximation

Abstract

This paper proposes fast opto-electrical transformation of high dynamic range (HDR) signals based on piecewise linear approximation. Non-linear transformation for the opto-electrical transfer function (OETF) is accelerated via two-level look-up table (LUT) linear approximation. First, the range of an input optical signal is divided into 10 intervals of a log10 scale. Then, each log10 scale interval is again divided into multiple sub-intervals. For each sub-interval, the parameters of the linear function for approximation of non-linear transformation are stored in a LUT. Without computation of the parameters for a range, the output of the electrical signal level is easily computed with the linear function. The proposed algorithm was evaluated along with the OETF mapping algorithm (the so-called LUT-linear mapping) in the HDRTools package developed by the Moving Picture Experts Group (MPEG). The experimental results show that the proposed algorithm achieves time savings on average of 42.73% and has a negligible loss in peak signal-to-noise ratio compared to the LUT-linear mapping method.