The main function of a deinterlacer is to take an interlaced video frame which consists of 60 two-field interlaced fields of an NTSC analogue video signal or 50 fields of a PAL signal, and create a progressive scan output.
An iteration on bob deinterlacing is to average adjacent scanlines of two frames which can produce a smoother, although blurrier, image.
Even if a line doubler employs the merging method it cannot be considered an inverse telecine device if a frame rate of 60p other than the original 24p is obtained.
Line doublers have been replaced recently by video scalers which incorporate 3:2 pulldown removal and the ability to scale the image to the various screen resolutions used on modern projectors and displays.
However, line doublers such as the Open Source Scan Converter[1] have been developed to convert signals from older video game consoles and have found popularity among retro gaming enthusiasts due to their minimal contribution to input lag.