MOTU micro express-USB, Руководство пользователя

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S Y N C H R O N I Z A T I O N W I T H T H E A V
127
Of course, if you want to stripe a tape and
meanwhile get on with other work, you can quit the
MIDI Timepiece AV software. Striping will
proceed in the background.
Striping frame-locked LTC onto video
The MIDI Timepiece AV can stripe LTC onto video
while syncing to the video, ensuring that the LTC is
frame-locked (i.e. LTC won’t drift out of sync with
the video frames).
When you do this, you are recording SMPTE time
code onto one of the two audio tracks on the video
tape. If you have a VTR that doesn’t allow you to
dub audio separately from video, you’ll have to dub
video at the same time. But while you are dubbing
audio (the new time code) with video, you also
have to send the same video signal to the VIDEO
IN port of the MIDI Timepiece AV so that it can
gen-lock to it. Therefore, to do all of this, you need
a video deck that can record audio independently
of video. If your video deck doesn’t support this,
you need:
■
two video decks, and
■
the ability to somehow split the video signal
coming out of one of them (such as a dual video
output, a separate video splitter, or video
distribution amp)
Let’s say that Video Deck 1 is the master, and Video
Deck 2 is the destination. You dub video from Deck
1 to Deck 2, while at the same time feeding the
video signal coming from Deck 1 to the MIDI
Timepiece AV, which is set to INTERN/VIDEO
sync mode. This makes the MIDI Timepiece AV
gen-lock to video (so that it is in sync with Deck 1
and Deck 2) and generate SMPTE time code,
which you feed into one of the audio tracks on
Deck 2. The result is a video tape in Deck 2 with the
original video plus frame-locked SMPTE time
code that came from the MIDI Timepiece AV.
☛
Important note: our tests have shown that you
will probably not get usable results if you attempt to
feed video from Deck 2 to the MIDI Timepiece AV.
You really need a bona fide video splitter to split the
signal from Deck 1 to both Deck 2 and the MIDI
Timepiece AV.
Striping SMPTE on a multitrack tape deck
The goal when striping SMPTE time code is to
generate an error-free signal strong enough for
reliable lockup, but not so strong that the SMPTE
bleeds through to adjacent tracks.
There are several ways to handle this. One way is to
leave an empty track on your multi-track tape deck
as a buffer between the SMPTE and other tracks.
With a buffer track, SMPTE can be recorded at
very strong (“hot”) levels (above 0 VU) without
risk of bleedthrough.
If your tape deck has no tracks to spare, a good
level at which to record is around –3 VU. That is,
the VU meter for the SMPTE track on your tape
deck should read –3 when you stripe the SMPTE.
This records SMPTE that is hot enough for reliable
lockup and weak enough so that it will not bleed
into adjacent tracks. -3 VU is only a rule of thumb,
though, so don’t hesitate to use other levels if they
work better for you.
Regenerating fresh time code (‘jam syncing’)
SMPTE is a problem when you are copying tapes: it
degrades rapidly every time you try to copy it from
one tape to another. Often, the SMPTE signal
deteriorates so much that it will not be
recognizable by any SMPTE-to-MIDI converter,
including the MIDI Timepiece AV, and you will no
longer be able to lock to it.
The solution to this problem is to use the MIDI
Timepiece AV to regenerate fresh SMPTE time
code that matches the original time code while you
are copying the tape. Some people refer to this
process as
jam syncing . When the MIDI
!USB Interfaces Manual Book Page 127 Tuesday, October 10, 2000 12:43 PM