I think I understand Force Film/IVTC - Please verify...

[Boathouse]

I think I understand Force Film & IVTC, please can you let me know if I'm correct on the following points...

* Some movies are stored on DVD in a FILM format at 24fps. When played on a NTSC DVD player these are speeded up to 29.760fps using a method called 3:2 pulldown.

* Therefore in DVD2AVI if a movie is displayed as FILM or FILM 95%+ then we should use the FORCE FILM option which will alter the frame rate to 23.976fps.

* Some movies are stored on NTSC DVD's at 29.760fps and these show up as NTSC in Avisynth. We should use IVTC, not FORCE FILM, with these movies to reduce the framerate to 23.976.

* If we use FORCE FILM on a movie where IVTC should have been used, we'll notice interlacing artifacts in the playback.

* But confusingly... Gordian Knot warns that IVTC should only be used as a last resort. So I've tried FORCE FILM on movies that are shown as NTSC in DVD2AVI and they came out fine!

* Perhaps the answer is to always use FORCE FILM first, and if problems arise then go back and do IVTC??

[Enchanter]

I have always preferred doing IVTC using TMPGEnc and more recently, GK 0.26. They work perfectly with all sorts of NTSC materials and somehow the framerate is converted into better (more correct) figures (23.97fps compared to DVD2AVI's 24.00fps).

[De Joker]

There is a very good article at doom9.org explaining ntsc, pal, ivtc, forced film etc.. also when to use forced film and when to use ivtc and when to use deinterlace etc.

I can't remember the exact adress, but i think it's definitly worth a read.

Robert

[khp]

http://www.doom9.org/ivtc-tut.htm