I have recently run into a problem with a video source thats supposed to be interlaced @ 29.970fps. Most material I have run into have been telecine video from 24fps to 29.97fps. The normal procedure is to IVTC the video -> encode it -> apply a 2:3 pulldown -> mux it. The source is a DVD title ( a collect of The Cure videos ). DVD2AVI didn't detect IVTC or such so I used avisynth and looked at the frames with virtualDub. I have found a pattern of 6 frames.

The first frame (of sixth ) is progressive even though the video is supposed to be interlaced, the second frame is barely noticable as interlaced, the third and fourth are truely interlaced, the fifth frame has the second field of the fourth frame as its first field and second field is that of the sixth frames first field, the sixth frame is interlaced.

From what I have read: if the source was originally 24fps and was converted to 29.97fps, then the fields should look like this->

field one : ABCD <- 24fps
field two : ABCD

field one : AABCD <- 29.97fps coverted from 24ps
field two : ABCDD

field one : A1 B1 C1 D1 D2 E1 <- 29.97fps converted from 25fps?
field two : A2 B2 C2 D2 E1 E2 <- A1 and A2 is a progessive frame
regardless if its in high motion or
not.

I figured since the music videos are from a band based out of Europe, that the video was probably originally 25fps. I have heard that the film to PAL conversion is just to speed up the film, so my theory of the original video being 24fps film -> converted to 25fps -> and then converted to 29.97fps doesn't seem practical.

I could delete every fifth frame, but what do I do with the first frame? If the source is supposed to be interlaced, then why is the first frame progressive?

Any help would be appreciated!