What does it mean to deinterlace video?
Deinterlacing is the process taking a stream of interlaced frames and converting it to a stream of progressive frames. Ideally, each field becomes its own frame of video, so an interlaced NTSC clip at 29.97 frames per second stream becomes a 59.94 frame per second progressive. Since each field is only half the scanlines of a full frame, interpolation must be used to form the missing scanlines. There are various methods of doing the interpolation, ranging from simply doubling scanlines to motion-adaptive methods. In many computing applications, deinterlacing is part of a recompression process, for example, converting a DVD of music videos in interlaced MPEG2 format to a progressive MPEG4 stream. For these applications, an output framerate of 59.94fps or 50fps is too high. Instead, most deinterlacer filters convert every interlaced frame to one single progressive frame, effectively halving the framerate of the content.
