About reverse telecine, A b c d, 67% resize factor – Apple Compressor (4.1.2) User Manual
Page 72: Chapter 5 advanced tasks 72
Chapter 5
Advanced tasks
72
About reverse telecine
Telecine is the process of converting motion picture film to the NTSC video format used in
broadcast television. The most common telecine approach to converting film’s standard 24 fps
frame rate to NTSC video’s 29.97 fps frame rate is to perform a 3:2 pulldown (also known as a
2:3:2:3 pulldown). If you alternate recording two fields of one film frame and then three fields of
the next, the 24 frames in 1 second of film end up filling the 30 frames in 1 second of video.
3:2 Pull-Down
Before (23.98 fps)
One second
A B C D
A A B B B C C D D D
Field
1
Field
2
Field
1
Field
2
Field
1
Field
2
Field
1
Field
2
Field
1
Field
2
A B C D A
D A B C D A B C D A B C D A B C D
B C
B
A B B C
C D D
A A B B B C C D D D A A B B B C C D D D A A B B C C D D D A A B B
B
C
C D D D A B
A B B C
C D D
B
After (29.97 fps)
A
D
D
As shown above, the 3:2 pattern repeats after four film frames.
For editing and effects purposes, it’s often desirable to remove the extra fields and restore the
video to its original 24 fps rate. This process is known as reverse telecine. An additional benefit of
restoring the original is that it’s easier to convert this to PAL, the European broadcast standard,
which uses a 25 fps frame rate.
The lower frame rate also has the advantage of requiring fewer frames per second of video,
leading to smaller file sizes. The reverse telecine feature in Compressor makes it easy to do
this conversion.
3:2 Pull-Down Removal
One second
After (23.98 fps)
Before (29.97 fps)
B
A B B C
C D D
A A B B B C C D D D A A B B B C C D D D A A B B C C D D D A A B B
B
C
C D D D A B
A B B C
C D D
B
A
A B C D A
D A B C D A B C D A B C D A B C D
B C
A A B B
B
C C
D
D D
Field
1
Field
2
Field
1
Field
2
Field
1
Field
2
Field
1
Field
2
Field
1
Field
2
A B C D
D
D
67% resize factor