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SMPTE SYNCHRONIZATION

Take care after using the offset/start time

The LTC Start setting in the Express interface

serves as the start frame when striping, but also as

the offset when reading. If you stripe at 1 hour

(1:00:00/00) and then lock to the time code you

just striped — without readjusting the offset/stripe

setting back to zero (0:00:00/00), then the

Express interface converts starting at 2 hours

(2:00:00/00).

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.

LTC MODE

In LTC mode, your Express interface locks to

incoming SMPTE time code received on its

SMPTE IN jack. But LTC mode differs from LTC

QuikLock mode in several signiﬁcant ways. In LTC

mode, your Express interface:

■ Emits regenerated LTC on its SMPTE OUT jack

■ Analyzes incoming time code and responds in

several useful ways, depending on what happens to

the incoming time code

■ Measures incoming time code with an extremely

accurate internal clock to see how fast or slow it is

running and displays the results in the SMPTE

Reader window in Express Console

Because LTC mode employs a sophisticated phase-

lock synchronization engine in your Express

interface, the amount of time it takes to establish

lockup to incoming time code is considerably

longer than LTC QuikLock mode. On the other

hand, LTC mode offers the additional capabilities

mentioned above. These features, and how you can

use them, are discussed in the next few sections.

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 your Express interface, and you will no

longer be able to lock to it.

The solution to this problem is to use your Express

interface 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 your Express interface

receives a SMPTE signal on its SMPTE IN cable, it

always regenerates a fresh signal that exactly

matches the incoming signal and sends it out the

SMPTE OUT cable (except for drop-outs, which it

eliminates with freewheeling).

!USB Interfaces Manual Book Page 74 Tuesday, October 10, 2000 12:43 PM

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