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Scan conversion or scan rate converting is a technique for changing the vertical / horizontal scan frequency of video signal for different purposes and applications. The device which performs this conversion is called scan converter. The application of scan conversion is wide and covers video projectors, cinema equipment , TV and video capture cards, standard and HDTV televisions, LCD monitors and many different aspects of picture and video processing. Scan conversion involves changing the picture information data rate and wrapping the new picture in appropriate synchronization signals. There are two distinct methods for changing a picture\'s data rate: * Analog Methods (Non retentive, memory-less or real time method) This conversion is done using large numbers of delay cells and is appropriate for analog video. * Digital methods (Retentive or buffered method) In this method, a picture is stored in a line or frame buffer with n1 speed (data rate) and is read with n2 speed, several picture processing techniques are applicable when the picture is stored in buffer memory including kinds of interpolation from simple to smart high order comparisons, motion detection and … to improve the picture quality and prevent the conversion artifacts.