Avid Technology Pro Tools SYNC HD, Manual

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Chapter 6: Additional Synchronization Information 57
Chapter 6: 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 distributed source,
such as a video distribution amplifier, or the house
video reference/black burst output of another de-
vice in the chain.
Resolving to video instead of house video
reference (black burst)
There are several reasons why you would resolve a
SYNC HD to a video signal rather than house syn-
chronization.
When House Video Reference is Unavailable
Re-
solve to a video signal whenever you are synchro-
nizing 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 synchronization capa-
bility (including consumer grade VCR, or some
entry-level computer-based editing 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 satisfac-
tory. In these situations, proper synchronization
can be achieved using the video signal as clock ref-
erence.
Why VITC is Unavailable for Clock Reference
VITC itself does not provide clock information di-
rectly as part of its timecode information, only po-
sitional information. However, since VITC is al-
ways 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 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, regardless
of whether it is being regenerated or generated.
By monotonic , it is meant that the VITC should be
smoothly ascending or descending, with no re-
peated or skipped frame addresses. In order to
achieve monotonicity, the external positional ref-
erence (while regenerating) or the clock source (in
Generator Preset Mode) must be synchronous with
the video signal onto which the VITC is being in-
serted.