This is (yet another) port of a filter by Donal Graft. Its aim is to remove combing, including inverse telecine. Note that it does not alter framerate. It merely deinterlaces the video, which can result in more frames than you need, depending on your video source and your desired output framerate.
For DVD sources specifically, this filter is strongly recommended instead of most others. Decomb is the “default” Inverse Telecine (IVTC) for many video encoding programs, including Gordian Knot and Avidemux. It is the only filter that can handle all possible combinations of frame reconstruction, decimation and deinterlacing.
If results are not satisfactory, you may wish to look at the filter Yadif which is also an excellent deinterlacer, though not as well adapted for true DVD Telecine video.
If the source video is 29.97 fps (or 30 fps), and you want to keep that framerate, then all you need to do is deinterlace the video with Decomb Telecide and nothing else.
If the source video is 29.97 fps (or 30 fps), and you want to transform it to 23.976 fps (or 24 fps), do the following: