A general purpose scan converter for converting video signals from one scan rate to another scan rate. The scan converter accepts NTSC, PAL, EGA, VGA, or other inputs in standard video formats and convert them to be displayed on a monitor Several modes of operation including continuous frame grabbing, grab and hold image, and dynamic scaling are provided. In addition, window sizing and window location options are under user control. The input sources for video may be selected, and a robust voltage controlled oscillator is provided for timing. The converter device operates continuously in real time and provides a high resolution output signal to a monitor. Special effects such as clipping of overlapping windows, superimposing graphics or text, and animation are supported.