Avid Technology Digidesign USD User Manual page 66

front panel Clock Reference switch to se-
lect VIDEO as the Clock Reference, it's re-
ferring to the Video Ref connector, and
never to the Video In connector.
To avoid the chance of this limitation get-
ting in your way, we suggest that you con-
nect your reference video feed (from a
black burst or colorbar generator) to the
Video Ref input, and use this input as your
Clock Reference whenever you want sam-
ple clocks locked to video.
Using Video Inputs with VITC and the
Character Generator
Unlike selecting a video input to use for
Clock Reference, you don't have freedom
to arbitrarily choose which input to use for
VITC and character generator functions.
Video Ref In
Video In
LTC
AES/EBU
Word Clock
Super Clock
Pilot Tone
Bi-phase/Tach
Figure 3. Video Input Flow diagram
62 Universal Slave Driver
A
Time Code and
Window Dubbing
B
Video Routing
Video routing is automatically switched within the
Universal Slave Driver, according to the Positional Reference
and Clock Reference settings:
• Route A — Positional Reference = Generate;
• Route B — Any other combination of Positional Reference
Sample Clock
Resolver Circuit
Clock Reference
Setting
The rule defining which video input is used
for VITC and character generator functions
is simple, and is explained in the following
sections and in Figure 3.
If the Clock Reference is one of the two
video inputs, and the Positional Reference
is Generate, then VITC and character gen-
erator functions are applied to the video ar-
riving at the Video Ref input connector.
This helps you avoid re-patching video ca-
bles whenever you want to stripe a video-
tape with your reference black burst or
color bars, along with internally generated
time addresses for VITC (and/or LTC,
and/or CG dub window). In Figure 3, this
scenario is identical to "Route A."
Video Output
Circuit
Clock Reference = Video Ref In or Video In
and Clock Reference settings
Word Clock Output
Super Clock Output
AES/EBU Output