Specifications

Chapter 4: Using SYNC I/O 43
Make sure you select the appropriate clock refer-
ence, sample rate, frame rate, and freewheel du-
ration. Also make sure the LTC signal is routed
properly to the SYNC I/O LTC In connector.
Freewheel Duration
Freewheel duration (time code freewheel) con-
figures SYNC I/O for a maximum number of
frames it should continue generating if time
code drops out or is otherwise interrupted. Free-
wheel settings are ignored when SYNC I/O is in
Internal/Generate mode.
Example of Time Code Freewheel
In a 30 fps Pro Tools session, if Freewheel Dura-
tion/Time Code Freewheel is 28 frames,
SYNC I/O will continue to generate until either
the incoming time code signal is restored, or un-
til 28 frames elapse, whichever occurs first.
To set freewheel duration:
From Pro Tools:
■ In the Time Code Settings section of the Ses-
sion Setup window, enter a number of frames for
time code Freewheel.
From the front panel:
1 Press Set, and use the Up or Down switches to
display Freewheel Length (FrEE LEn).
2 Press Set to display freewheel duration
choices.
3 Use the Up or Down switches to scroll
through available choices (lowest is “4 Fr” or
four frames, highest is “40 Fr” or 40 frames).
4 Press Set.
From SYNC I/O Setup software utility
(Windows only):
■ Choose a value from the Freewheel Duration
menu.
VITC and Positional Reference
VITC is a commonly used positional reference
in professional audio post-production. Since
VITC is time code information that is embedded
as part of the video signal, VITC can be read
when the VTR is paused or crawling slowly.
When working with Pro Tools, this means that
VITC can be used for Auto-Spotting regions to
particular video frames.
VITC is less prone to tape drop outs, and in this
sense, is inherently more reliable than LTC.
VITC can be embedded into any video signal,
including digital video signals (tape or nonlin-
ear), without requiring an extra audio track to
carry time code.
Tape Protection Mode and VITC
In order for VITC to be read when a videotape is
paused, the picture must remain visible. How-
ever, to reduce wear on the video heads, after a
few minutes of still/pause mode, many VTRs
will automatically drop into stop mode—which
means the tape will be disengaged from the
heads, and VITC can no longer be read off the
tape. To continue reading VITC, you may need
to reengage still/pause, or press play and re-
shuttle the tape to the desired frame.
Clock Considerations for VITC
To avoid tape protection mode problems and
ensure constant clock referencing, use the Video
Ref In as your clock reference instead of Video
In, whenever possible. When using Video Ref In
(and house sync), if the video picture disappears
SYNC I/O will remain resolved to the black burst
signal at the Video Ref In connector.