Sampling and Reconstruction of NTSC Video Signals at Twice the Color Subcarrier Frequency

Methods for sampling and reconstruction of NTSC video signals at twice the color subcarrier frequency are described and evaluated. A scheme for sampling NTSC signals is characterized by the horizontal sampling frequency and the spatiotemporal sampling structure. For a given sampling frequency, the sampling structure should be chosen to permit the best subjective reconstruction of the analog signal. This paper presents a three-dimensional analysis of sampling structures suitable for sampling NTSC signals at twice the color subcarrier frequency, and describes a method for designing the reconstruction filters. Three sampling schemes were simulated on a number of sequences of NTSC video, and evaluated in a subjective test. The field quincunx (QT) sampling structure was found to give best results. There was no detectable subjective difference between the original and reconstructed sequences in most cases. Minor degradations were detected for some critical images, upon close inspection.