Flicker correction for archived film sequences using a nonlinear model

摘要

A new model for the correction of flicker in archived film sequences is formulated from first principles. The model takes into account the Hurter-Driffield density versus log exposure characteristic to estimate image intensity errors caused by exposure inconsistencies. The model is shown to be highly nonlinear and can accommodate typical grayscale manipulations performed during film-to-video transfers. Motivated by the above model, an algorithm for the estimation of a correction profile across the available grayscale is developed. This profile is obtained from histogrammed gray-level differences between a reference and a degraded frame and is robust with respect to intensity changes due to scene and camera motion. Our results show that the proposed algorithm is very effective toward removing flicker for a variety of archived sequences and compares favorably with other state-of-the-art techniques developed for the same purpose. Additionally, the parametric form of the profile makes it particularly suitable for metadata use and allows fast inversion of the restoration process and recovery of the original material.