DigiDesign SYNC HD, Manual

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Appendix A: Additional Synchronization Information 69
appendix a
Additional Synchronization Information
Video and VITC Signals
Black Burst and House Video Reference
A black burst signal is essentially a “position-
less” video signal. As with any “shared” video
signal, you’ll want to ensure that your video
feed comes from a properly buffered and distrib-
uted source, such as a video distribution ampli-
fier, or the house video reference/black burst
output of another device in the chain.
Resolving to video instead of house video
reference (black burst)
There are several reasons why you would resolve
the SYNC HD to a video signal rather than
house synchronization.
When House Video Reference is Unavailable Re-
solve to a video signal whenever you are syn-
chronizing Pro Tools (or other device) to video,
and you either:
• Do not have a house video reference.
– or –
• Your setup includes equipment that lacks
house video reference input and synchroniza-
tion capability (including consumer grade
VCR, or some entry-level computer-based ed-
iting systems).
Simple Setups
In a modest setting with one or
two VTRs, Pro Tools, and a SYNC HD, using the
video signal as the clock reference is often satis-
factory. In these situations, proper synchroniza-
tion can be achieved using the video signal as
clock reference.
Why VITC is Unavailable for Clock Reference
VITC itself does not provide clock information
directly as part of its time code information,
only positional information. However, since
VITC is always embedded into a video signal,
that video signal can be used as a clock reference
by selecting Video Input as the clock reference
(or Video Ref In if your facility has a house video
reference).
VITC Timing Rule
The following rule is in effect whenever you are
generating or regenerating VITC.
‹
Inserted VITC should be monotonic, regard-
less of whether it is being regenerated or gener-
ated.
By monotonic , it is meant that the VITC should
be smoothly ascending or descending, with no
repeated or skipped frame addresses. In order to
achieve monotonicity, the external positional
reference (while regenerating) or the clock
source (in Generator Preset Mode) must be syn-
chronous with the video signal onto which the
VITC is being inserted.