Filter
Top Products
Chapter 16, SMPTE Synchronization Overview
ALESIS M20 REFERENCE MANUAL 1.06 16-5
16.3 OFFSETS IN THE M20
An offset is an intentional difference in location between decks. In the simplest situations,
offsets are not required: when it’s 2 o’clock on the master, it’s 2 o’clock on all the slaves. But
more often, tapes were recorded at different times, in a different order, and now must be
edited together at a particular sync point.
In particular, in the M20, there are two different Chase References which may provide time
code: ABS time and Tape (SMPTE) time code. Most of the time, these two time codes will
not numerically match (although they should advance at exactly the same rate). You may
use offsets to transform any ABS or SMPTE location to any time code desired, depending on
the needs of your project.
Example: While ABS time always begins at 00:00:00 on every ADAT tape, it is
customary for SMPTE time code to start no earlier than 00:58:00:00. You can set the
ABS offset so that the internal generator will issue SMPTE time code at 58 minutes
after midnight at the actual ABS location zero.
There are three different places to set offsets in an M20 system:
16.3A SMPTE CHASE OFFSET
This is set in the first page of Edit SMPTE Chase mode (see section 11.6a).
The SMPTE Chase Offset is used to offset the M20 from incoming time code. It is added to
the ABS time to equal the SMPTE Tape Counter display. If the M20 is slaving to an external
time code source, the SMPTE Chase Offset will be added to the Chase Reference (either ABS
or Tape TC) to offset the M20 from the incoming master time code.
Example: If the SMPTE Chase Offset is 4 hours, and the Chase Reference is ABS time,
and the Timecode Source is External, when the SMPTE IN reference counter is
04:30:15, the M20 will chase to ABS location 00:30:15.
Note: The Tape Counter SMPTE display is always based on ABS Time plus the SMPTE Chase
Offset, even when the Chase Reference is set to Tape TC. This may lead to
confusion in applications where Tape TC was recorded without reference to the
ABS time for some reason. But despite the “SMPTE display” not matching the
incoming time code, it does synchronize and chase to the Tape TC plus the SMPTE
Offset. To avoid confusion, turn the Tape Counter to ABS.