Avid Technology Digidesign USD, Руководство пользователя, Страница: 44 / 96

Universal Slave Driver 40
To set freewheel duration from Pro Tools:
1
Choose Display > Session Setup.
2
In the Time Code Freewheel section, en-
ter a number of frames for time code free-
wheel.
To set freewheel duration from the front
panel:
1
Press Set, then use the Up or Down
switches to show Freewheel Length (FrEE
LEn) in the LED display.
2
Press Set again to access freewheel dura-
tion choices.
3
Use the Up and Down switches to scroll
through available choices (lowest is “4 F4”
or four frames, highest is “40 Fr” or 40
frames).
4
When the desired freewheel duration is
displayed, press Set.
To set freewheel duration using USD Setup:
■
Choose the desired amount from the
Freewheel Duration menu.
VITC and Positional Reference
VITC is a commonly used positional refer-
ence in professional audio post-produc-
tion. Since VITC is time code information
that is embedded as part of the video sig-
nal, 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 partic-
ular 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 nonlinear), without requiring an
extra audio track to carry time code.
Tape Protection Mode and VITC
In order for VITC to be read when a video-
tape is paused, the picture must remain vis-
ible. However, to save wear-and-tear on
video heads, after a few minutes of
still/pause mode, many VTRs will automat-
ically drop into stop mode—which means
the tape will be disengaged from the video
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 in-
stead of Video In, whenever possible.
When using Video Ref In (and house sync),
if the video picture disappears the USD will
remain resolved to the black burst signal at
the Video Ref In connector.
To use VITC as the USD positional reference
using Pro Tools:
1
Open the Session Setup window.
2
Use the Positional Reference pop-up
menu to select VITC.