User`s guide

Pro Tools Reference Guide334
Typically during the Telecine process, a
master digital video tape is created, along
with a work copy on 3/4” analog video tape
for the picture editor to use. At the same
time, a new audio master may be created by
slowing down, or “pulling down” by 0.1%,
to compensate for the change in speed
from film to NTSC video.
Guide Tracks
In the Video editing process, the audio
track produced by the video editor (the
“guide track”) is rough and needs to be en-
hanced and improved by the audio engi-
neer. For this reason, the audio engineer
will need to re-edit the original sound ele-
ments in a process known as conforming.
3:2 Pulldown
A film clip that lasts 1000 seconds consists
of 24,000 film frames (pictures). If you
want to transfer that film to 1000 seconds
worth of NTSC color video, you have to
“fit” 24,000 film frames into 29,970.02997
video frames.
If we use the black and white NTSC video
standard (30 FPS) instead of 29.97 FPS, the
process of converting film frames to video
frames is greatly simplified. Now instead of
any fractional frames, we have 24,000 film
frames going into 30,000 video frames
(60,000 video fields). In the Telecine pro-
cess (for NTSC color video), each odd film
frame is copied to two video fields, and
each even film frame is copied to three
video fields, creating what is called a
3:2 Pulldown. The speed of the film is also
“pulled down” to 23.976 FPS in order to ac-
commodate the slower speed of NTSC color
video compared to NTSC black and white
video (29.97 FPS compared to 30 FPS.
The Telecine stage of video post-production
Telecine machine
converts film frames
to video fields using
Digital video
3:2 Pulldown
Analog video
“work tape”
master
Production audio
30 FPS Non-Drop
48 kHz
Telecine
29.97 FPS
48 kHz
Sample rate conversion
or A-D-A (analog stage)
29.97 FPS
29.97 FPS
“simo” DAT
How film frames translate to video fields in a
3:2 Pulldown
1 1 1 2 2 3 3 3 4 4
1
2
3
4
Film frames
Video fields