MOTU micro express-USB, Руководство пользователя

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U S I N G M I C R O E X P R E S S C O N S O L E
42
Frame lock
The Frame lock check box is only available when
LTC or MTC is chosen as the master sync source. It
is not available when you are using internal mode
or LTC QuikLock mode.
To understand the Frame lock option, you first
need to know that the Micro Express continuously
monitors the time code to which it is locked (either
LTC or MTC) to detect any possible discontinuity
in the frame times as they advance. If the Micro
Express detects more than five frames in a row that
are not continuous with respect to previous frames
received, then it does one of two things, depending
on whether the Frame lock option is turned on
(checked) or off (unchecked).
If the Frame lock option is turned on (checked),
and the Micro Express detects more than five
frames in a row that are not continuous with
respect to previous frames received, then it will
stop converting altogether.
If the Frame lock option is turned off (unchecked),
and the Micro Express detects more than five
frames in a row that are not continuous with
respect to previous frames received, then it begins
to perform a kind of “pseudo jam sync”. In this
mode, it continues to convert an uninterrupted
stream of continuous time code, while at the same
time clocking off of the incoming LTC or MTC.
Even though the frames it is generating no longer
match the frames it is reading, it will continue to
remain in sync with the incoming time code.
In other words, when the Frame lock option is off ,
the Micro Express will ignore discontinuous jumps
in the time encoded in the incoming time code by
clocking itself off of the incoming time code
without stopping (or pausing) and continuing to
convert a continuous, uninterrupted stream of
frame times based on the time code to which it first
locked.
Turn on Frame lock when you want the Micro
Express’s frame times to match incoming frame
times, and you want to stop converting altogether if
there are jumps in incoming time code.
Turning off Frame lock can be a life saver if you find
yourself in a situation where you have time code on
tape (or other source) but the frame locations jump
around to different times (because of overlapping
SMPTE striping, edits, or whatever). By turning off
Frame lock, you can sync continuously to this type
of timecode without glitching or stopping. If the
SMPTE on your tape jumps around as described,
you are likely to experience brief drop-outs at the
points where it jumps. If so, just increase the Micro
Express’s freewheeling to cruise past them.
Jam for
The “Jam for” setting determines how many frames
the Micro Express will run on its own when it
encounters a drop-out in incoming time code. For
details, see “Freewheeling to avoid time code
dropouts” on page 72.
When you choose Jam for infinity , the Micro
Express begins generating time code on its own
indefinitely as soon as it stops receiving incoming
time code. And it will continue to do so until you
either stop it with the STRIPE button on the front
panel or by changing the source (or “Jam for”
amount) in the Sync window.
Still-frame sensitivity
The Still-frame sensitivity option applies to
situations in which you are feeding time code
(most likely LTC) to the Micro Express, and the
time code continues (the same frame over and over
again) even when its source is parked on a frame.
For example, you might be using a VITC-to-LTC
converter that continuously sends time code when
video is paused.
!USB Interfaces Manual Book Page 42 Tuesday, October 10, 2000 12:43 PM