This is a port of Yadif (Yet Another De-Interlacing Filter) from MPlayer. The original filter was written by Michael Niedermayer. Later it was ported to Avisynth by Fizick and finally ported to Avidemux by Mean.
For telecined DVD sources specifically, Decomb Telecide is strongly recommended instead of this filter.
When compared with other deinterlacing filters available in Avidemux, some users and testers believe this is the best general purpose deinterlacing filter. Comparison test showed a consistent high quality of interlaced image blending with very little artifacting while maintain a smooth playback and individual frame picture. It also has the side benefit of being remarkably fast. It has also been found to work very well with MythTV video that has not been deinterlaced at all, producing nice finalized film.
This deinterlacing filter checks pixels of previous, current and next frames to re-create the missed field by some local adaptive method (edge-directed interpolation) and uses spatial check to prevent most artifactes. This filter is known to give pretty nice results with a wide range of sources, while being significant faster than TDeint.
Further information and discussion can be found at Doom9's forum.