ABSTRACT
Converting a three-dimensional moving image into a video signal requires a method of accurately translating light into electricity and then back into an image viewed on a TV monitor. This translation involves adopting a standard signal with a method of synchronization of line and frame repetition at the point of production, transmission and reception/video replay. There are many variables in the way this translation is accomplished:
The number of lines in the picture and the number of pictures per second in monochrome television broadcasting were historically chosen to be compatible with the frequency of the AC power supply. There were 50Hz countries and 60Hz countries and so there arose over time two major scanning standards of 625 line/50 frames per second and 525 line/59.94 frames per second.
A further division was established with the introduction of colour when different regions of the world chose different colour encoding systems such as NTSC, PAL and SECAM.
The colour signal can be passed through the production chain either as a composite signal or as a component signal (see page 15).
The aspect ratio of the broadcast image (the ratio of the width of the image to its height) added another variable with ratios varying between 4:3, 16:9 and 14:9. Also methods of transmitting film images with other aspect ratios were evolved.
The conversion of an analogue signal into a digital signal introduced other variables depending on the sampling rate and the degree of compression employed.
