I decided to start creating promised AviSynth plugin for manual IVTC by allocating clip boundaries in which cadence changes, removing Pulldown cadence in this clip, replacing lost fields with a copy of previous frame, duplicating frames (+1 to frame count), removing duplicates (manual decimating, -1 to frame count), checking for out of sync, etc. A little later after creating plugin, I will write a manual: how to determine interlace frames and cadence, which is used throughout video in cropped form (duplicate detection in places with small movement, detection by noise, detection by resolution drop in one frame, detection with invert, etc.). To implement support for all types of Pulldown, I need to know how they are arranged, using scheme. DGPulldown is crashing.
In Internet, I found information only about:
1. differences between 3:2, 2:3, 3:2:3:2, 2:3:2:3
2. scheme for 2:3:3:2, but I'm not sure that scheme is not confused with 3:3:2:2 or 2:2:3:3
3. 2:2:2:2:2:2:2:2:2:2:2:3 (12:1, 24:1), described only in words, I still do not understand how it works: 11p frames and 1i duplicate or 12p frames and 1i duplicate
For remaining cadences I did not find description or scheme in Internet.
Tell me any site or pdf, where there is a scheme for following types of Pulldown:
2:2:2:2:2:2:2:2:2:2:2:3 (24:1, 12:1)
And explain to me what mean numbers 2, 3, 4, how are composed these titles (2:2, 3:3, etc.)?
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Last edited by Megafox; 19th Sep 2018 at 04:24.
It's very simple: Each number represents one film frame and the value indicates the number of video fields over which the film frame is displayed.
2:3 pulldown means the first film frame is displayed for the duration of 2 video fields, the next film frame is displayed for the duration of 3 video fields. So 2 film frames becomes 5 video fields (2.5 video frames), then the pattern repeats. The repeating pattern means 2:3 pulldown is exactly the same thing as 2:3:2:3 pulldown. The reason it's sometimes called the latter is to give a whole number of video frames -- ie, 4 film frames becomes 10 video fields (5 video frames). It's especially useful to think of it this way when it comes to inverse telecine -- since you are dealing with an integer number of video frames.
2:3 and 3:2 are essentially the same thing. It's just a matter of where you start. In practice, when you capture video you have no control over the starting frame so a movie broadcast with 2:3 pulldown may appear as 3:2 pulldown in your cap.
Likewise 2:3:3:2, 3:3:2:2, and 2:2:3:3 are all essentially the same thing, differing only in where you start. And again, when you capture you have no control over which frame you start so you may get any of those patterns in the cap.
2:2:2:2:2:2:2:2:2:2:2:3 means the first film frame is displayed for the duration of 2 fields, the next for 2 fields... until frame 12 where a film frame is displayed for the duration of 3 fields. Then the sequence repeats. This converts 24 film frames to 50 video fields without changing the running time (no PAL speedup or pitch change). When this is captured and packaged as frames you get progressive looking frames for half a second followed interlaced looking frames for half a second.
You should be able to figure the rest out on your own now.
2:2 - AA BB
2:3 - AA BB B|C CD DD
3:2 - AA AB B|C CC DD
2:3:2:3 - AA BB BC CD DD
3:2:3:2 - AA AB BC CC DD
3:3 - AA AB BB
2:3:3:2 - AA BB BC CC DD
3:3:2:2 - AA AB BB CC DD
2:2:3:3 - AA BB CC CD DD
2:2:2:4 - AA BB CC DD DD
2:2:3:2:3 - AA BB CC CD DE EE
2:2:2:2:2:2:2:2:2:2:2:3 - AA BB CC DD EE FF GG HH II JJ KK LL L|M MN...
Last edited by Megafox; 19th Sep 2018 at 08:49.
So for 2:3 or 3:2 pulldown:
# 24 frame per second source to 60 field per second video ChangeFPS(60) # duplicate frames AssumeTFF() # make top field first video SeparateFields() SelectEvery(4,0,3) # select alternating top and bottom fields, 60 fields per second Weave() # 30 frames per second
Of course, all this happens too fast to actually "see". All you notice is a slight flicker.
For hard-coded pulldown, the pattern can be anything, although 3:2 cover 99% of the material most people will see. When I used to make DVDs from amateur film, and that film was shot at 12, 15, 16, or 18 fps, I created the appropriate field-by-field pulldown using AVISynth and, more recently, simply using Vegas with "smart resampling" disabled. When I've later had to IVTC some of this material, I use this AVISynth script:
tfm(display=false) tdecimate(display=false,mode=0,cycleR=2,cycle=5) #18 fps # 3:3:4 field count #tdecimate(display=false,mode=0,cycleR=7,cycle=15)#16 fps