Specifications
Pro Tools Reference Guide574
29.97 fps Non-Drop Rate Not Recognized
29.97 fps Non-Drop is a slightly slower version
of 30 fps Non-Drop time code. When used with
color video, each video frame now matches up
with each SMPTE frame without having to use a
drop-frame coding. This makes any frame num-
ber mathematics much simpler, since no frame
numbers are dropped.
Unfortunately, some hardware and software de-
vices do not recognize 29.97 Non-Drop as a sep-
arate frame rate. For example, any standard
SMPTE-to MTC-converter does not explicitly
recognize it. The user must tell the convertor to
expect 30 fps Non-Drop instead. In fact, many
devices that read SMPTE work acceptably by
reading 29.97 Non-Drop if they are set to expect
30 fps Non-Drop.
Any SMPTE reader that uses the time code num-
bers to make real-time calculations (as Pro Tools
does when it tries to trigger and synchronize to
SMPTE) also needs to know that the frame for-
mat is 29.97 and not 30 fps. Since Pro Tools al-
lows this choice of frame rate this does not re-
ally pose a problem. The problem exists because
many users cannot readily distinguish 29.97
from 30 fps.
Even though NTSC tapes only use 29.97, some
production companies will distribute video
work prints striped with 29.97 fps but mark
them as “30 fps NTSC,” by which they actually
mean 29.97 fps Non-Drop.
By the time you get the tape, you may have no
idea what’s actually on it. Feeding 29.97 Non-
Drop to Pro Tools when it’s set for 30 fps Non-
Drop will result in timing errors of about 1.8
frames per minute, causing audio playback to
trigger out of sync.
Be Careful When Changing Frame Rates
If you change time code rates in the middle of a
session, many SMPTE-to-MIDI Time Code con-
verters need to be turned off and turned on
again to be able to recognize the new frame rate.
Use a Consistent Clock Source
When possible, sound files should be played
back using the same sync reference signal it was
recorded with. This assures the closest match be-
tween record and playback sample rates.
Disable Screen Savers and Power Management
Features
These types of software can cause your com-
puter to ignore MIDI data (such as MIDI Time
Code).