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What is 2-3 pulldown?
Frame rate of FILM is 24fps.
PAL video is 25fps.
When we play FILM thru PAL video, 25fps.
So motion is quicker and playing time is shorter 96% (24/25).
NTSC video is 30fps (to be exact, 30/1.001fps).
If we play FILM thru NTSC video as PAL
(1 frame on FILM is 1 frame on video),
motion will be quicker and playing time be shorter 80% (24/30).
It is too quick so it will not seem natural motion,
when we play FILM thru NTSC video, 1 frame on FILM is played
2 or 3 fields on video, so motion and playing time is same as FILM.
FILM frames 0--. 1--.--. 2--. 3--.--.
| | | | | | | | | |
NTSC fields 0T | 1T | 2T | 3T | 4T |
0B 1B 2B 3B 4B
In analog video world, this process is called 2-3 pulldown,
because NTSC video is repeating of 2 fields from original 1 frame
and 3 fields from original 1 frame.
What is 3:2 pulldown?
FILM is recorded in MPEG2 / DVD video for NTSC at 24fps
(to be exact, 24/1.001fps). Some flags are also recorded on each frame.
DVD video player use top_field_first flag and repeat_first_field flag
to play 30fps (to be exact, 30/1.001fps) for NTSC monitor.
FILM frames 0 1 2 3
top_field_first 1 1 0 0
repeat_first_field 0 1 0 1
FILM fields 0T 1T----. 2T 3T
| 0B | 1B | 2B | 3B-+--.
| | | | | | | | | |
NTSC fields 0T | 1T | 2T | 3T | 4T |
0B 1B 2B 3B 4B
This process is called 3:2 pulldown.
What is different 2-3 pulldown and 3:2 pulldown?
Results seem same.
Difference of name is maybe where to start counting:
2 fields or 3 fields.
2-3 pulldown is processed before recording and recorded at 30fps.
3:2 pulldown is processed at playing and recorded at 24fps.
If we play with progressive (60 frames/seconds) monitor,
2-3 pulldown video need rather complex process at progressive monitor
to display beautifully. This process isn't reliable perfectly.
When we play DVD 24fps video for 3:2 pulldown with progressive monitor,
if player and monitor connected with cable which support progressive,
player may directly generate progressive frames instead of normal
3:2 pulldown process. This is simple and reliable perfectly.
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