[HELP] PAL VHS capture issue

[Miranda]

One particular tape I captured recently seems to have a problem when de-interlacing to bob - it seems that during some scenes the frames flow one frame forwards and one backwards , instead of all frames flowing forwards naturally, and this makes the footage look jerky. I've not seen this happen with any other footage I have captured - any suggestions?

[Selur]

Sounds like the field order changed, what happens if you change the scan Type?

[Miranda]

I did try changing to odd, but same problem.

[Selur]

To the opposite, tff <> bff

[Miranda]

Tried both overwrite BFF and TFF, same problem. Baffled.

[Selur]

Okay, normally one should have forward-backward motion and the other not, if the source is interlaced. ([INFO] Interlacing patterns).
The source is interlaced, right?

Cu Selur

[Miranda]

Yes, it is interlaced, BFF from PAL 25i VHS. 

The vast majority of PAL VHS interlaced videos I bob deinterlace do not show the forward/backward movement when QTGMC to bob50 - how do I get rid of the backwards motion and make it all forward motion only?

OK, just seen you said apply VFF - this shoudl fix it.

[Selur]

That is a typo,.. there is no AssumeVFF I meant TFF there.
What I wrote there is to detect what the source is, not how to handle it.