I have a few NTSC DVDs that share some common features. Because of their distinctive encoding they are impossible to play directly on progressive video displays, and they are also very difficult to deinterlace.

I suspect these DVDs are all conversions of PAL-sourced material. The encoded framerate is 30000/1001, but the material is things like Australian Television shows or European made-for-TV movies.

Frame-by-frame these DVDs display a similar pattern: five interlaced frames followed by one progressive frame. In one instance the patter is four interlaced frames followed by two "lightly interlaced" frames that appear to be combinations of two different interlaced frames with one progressive frame.

It looks like all the information is present and if I understood the encoding method I could easily create a specialised "pullup" filter to generate a continuous stream of progressive frames at a different frame rate. Normal pullup filters do not work any better than deinterlacing filters. Both leave significant jitters every six frames. Does anyone know how these DVDs are being encoded?