MOTU micro express-USB, Руководство пользователя

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S M P T E S Y N C H R O N I Z A T I O N
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steadily as well. For the micro express, the lights on the front panel
are arranged slightly differently than what is show here on the XT, but
they perform in an identical fashion.
If the LOCK and TACH lights do not behave as
described, your Express interface is not
successfully locking to the SMPTE time code. This
could be a problem with the audio connections
between the tape deck and your Express interface.
It could also be that the SMPTE level is not high
enough. See Appendix C, “Troubleshooting and
Customer Support” page (149).
The SMPTE display in the Express XT Console
Toolbar
When the Express XT is shipped from the factory,
it is set up so that the MIDI Express XT Console
Toolbar SMPTE display will provide a running
update of the SMPTE time code being generated or
converted by the MIDI Express XT.
Routing MIDI Time Code
At times, you may need to route MIDI Time Code
to a device connected to one of the Express
interface’s MIDI OUTs. To route time code to a
MIDI OUT cable, use the MIDI Routing window in
the Express Console as described in “The Sync In
and Sync Out icons” on page 38 (for micro express
users) and “The Sync In and Sync Out icons” on
page 58 (for Express XT users). Connect the Sync
icon in the left-hand column of sources to the
desired MIDI output(s) in the right-hand column.
SMPTE Offset
When reading time code, there may be times when
you need to offset your Express interface a certain
amount from the time code you are feeding it. See
“Offset/start time” on page 43 (for micro express
users) or “Offset/start time” on page 63 (for
Express XT users) for details.
Freewheeling to avoid time code dropouts
When your Express interface encounters a drop-
out —a series of missing or unreadable frames—in
the SMPTE time code, it “freewheels” past them,
pretending that they were not missing by briefly
generating its own code to make up for the missing
frames. The default freewheel value is 4 frames.
This means that your Express interface will
continue to generate time code for four more
frames after it stops receiving time code. If it does
not receive any more time code after four frames, it
will stop converting.
The factory default base setups have the
freewheeling feature set to 4 frames for fastest
response when you stop the tape deck. The
Freewheel amount can be adjusted up to 32 frames.
This allows your Express interface to maintain
lockup even over lengthy SMPTE drop outs.
If you encounter a time code drop out that causes
your Express interface to stop converting for a
moment, try increasing the “Jam for” amount in
the Sync window. Try adding just a few frames at a
time when adjusting the amount. (For details on
the “one time jam sync” option, see “Regenerating
fresh time code (‘jam syncing’)” on page 74.)
your Express interface freewheels at the frame rate
it is reading at the time it begins freewheeling —
except for 29.97 drop and non-drop. If you intend
on reading 29.97 SMPTE, be sure to manually set
the SMPTE format to 29.97 so that freewheeling
will occur at the proper rate.
When you increase the “Jam for” amount, you also
increase the amount of time that your Express
interface keeps converting when you stop tape. To
make your Express interface as responsive as
possible, only raise the “Jam for” amount as high as
necessary to overcome the drop-out(s) you are
encountering.
Synchronizing to discontinuous time code
Your Express interface has the ability to stay in sync
with discontinuous time code — that is, time code
that has no gaps in it but does have jumps in its
frame locations. For details about how to do this,
!USB Interfaces Manual Book Page 72 Tuesday, October 10, 2000 12:43 PM