Avid Technology Digidesign USD, User Manual, Page: 45 / 96

Chapter 4: Using the USD 41
To use VITC as the USD positional reference
using the front panel:
■
Use the front panel Positional Reference
switch to select VITC.
To use VITC as the USD positional reference
using USD Setup:
■
Choose Vertical Interval Time Code
(VITC) from the Positional Ref pop-up
menu.
Additional VITC-Related Settings
USD Settings
Make sure to set the appropri-
ate clock reference, sample rate, frame rate,
and freewheel duration.
Connections and Sources
Make sure that
your VITC-striped video signal, if any, is
routed to the USD Video In connector (not
the Video Ref In connector). If you use a
black burst signal as clock reference con-
nect it to the Video Ref In connector.
You should consider using Video Ref as
your Clock Reference (rather than Video
In) when working with VITC because a
black-burst signal at the Video Ref input
will always be there, unlike the video signal
at Video In, which may disappear if the
videotape disengages.
Auto Switch LTC/VITC Positional
Reference
In Auto Switch mode, the USD switches au-
tomatically between LTC and VITC de-
pending upon which is delivering the best
time code signal. This is indicated on the
front panel by the LTC and VITC positional
reference LEDs (both will be lit), and by a
decimal point between the minutes and
seconds. on the front panel time code dis-
play.
VITC cannot be read at high speeds (shuttle
speeds, for example) while LTC can, and
LTC cannot be read at slow speeds (while
VITC can be read at slow speeds, and when
parked). Auto Switch LTC/VITC provides
the best of both LTC and VITC reading
without having to manually switch set-
tings.
To select Auto Switch LTC/VITC using
Pro Tools:
1
Open the Session Setup window.
2
Choose Auto Switch (LTC/VITC) from
the Positional Reference pop-up menu.
To select Auto Switch LTC/VITC using the
front panel:
■
Press the Positional Reference switch to
select Auto Switch LTC/VITC (indicated
when both the LTC and VITC LEDs are si-
multaneously lit).
To select Auto Switch LTC/VITC using USD
Setup:
■
Choose Auto Switch LTC/VITC from the
Positional Ref pop-up menu.
Make sure to select the appropriate clock
reference, sample rate, frame rate, and free-
wheel duration options.
Auto Switch LTC/VITC Requirements
• Make sure the LTC signal is routed prop-
erly to the USD’s LTC In connector;
• Make sure the VITC-striped video signal
is routed properly to the USD’s Video In
connector (not the Video Ref In connec-
tor);