A b c d, Chapter 7 advanced functions 174 – Apple Compressor (4.0) User Manual

Page 174

Chapter 7

Advanced functions

174

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

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 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

C D D D A B

A B B C

C D D

After (29.97 fps)

As shown above, the 3:2 pattern (actually a 2:3:2:3 pattern because frame A is recorded to two
fields followed by frame B recorded to three fields) 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 23.98 fps rate. This process is known as reverse telecine. An additional benefit
of restoring the original 23.98 fps rate 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)

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

C D D D A B

A B B C

C D D

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

C C

D D

Field

A B C D