Traditionally the technique to reduce the visibility of scan lines on large screen CRT-based displays has been to increase the number of horizontal scanning lines via special video processors called "line doublers", "line triplers", and "line quadruplers". The fundamental operation of these devices is simple: by increasing the number of horizontal scan lines in the image raster, the vertical line structure of the image becomes finer and significantly less visible. However, recent research into video raster smoothing techniques has revealed a superior method. As it turns out, the simple multiplication of a display's horizontal scanning frequency via integral multiples (2x, 3x, 4x), while easy to do electronically, usually produces a less than optimum effect. Too little multiplication still results in some scan line visibility, and too much actually causes scan lines to overlap thereby decreasing vertical resolution. Typically, the optimum scanning frequency, where the scanning lines just blend into each other, is between two integral scanning multiples (2x, 3x, 4x) and requires a "variable line multiplier" to obtain.

The DWIN TranScanner is a variable line multiplier built specifically for the home theater applications. It is designed so that one can dial-in exactly the right amount of line multiplication so that a video display's "optimum line density" is achieved. This optimum line density, which is characterized by the size of the projection CRT tubes and the size of the scanning electron beam, is the point where horizontal scan lines just blend into each other to produce a seamless, film-like image. Once the transcanner is programmed properly (during set-up), it automatically calculates the with the correct scanning frequency for different aspect ratio video sources. (if you look at the diagrams below you will see that different video sources have different numbers of scanning lines in the active image of the picture. This means that when you "blow up" that section of the image to fill a screen, a different scanning frequency is necessary to preserve the optimum line density).