Apple Logic Pro 9 - Manual (Page 1215)

• MTC Trigger + Auto Speed Detection: Similar to MTC Trigger (see below), but the tempo
of the time code master is constantly monitored while Logic Pro is open. The next
time you start Logic Pro, it will use an adapted sample rate. This mode keeps long
regions in better sync with the time code master, although not as closely as MTC
Continuous. It does, however, use a constant sample rate, which is not affected by
variations in the time code master signal.
• MTC Trigger: Audio regions are started in sync, but are then played at a constant
sample rate, regardless of any variations in the time code master signal. Logic Pro
always uses the set nominal sample rate (44.1, 48, 88.2, 96, 192 kHz). This mode is
suitable when it is vital to retain the absolute pitch of a recording. If the speed of the
time code master deviates from the nominal value, you may need to split long audio
regions into shorter sections.
• External or Free: Logic Pro has no influence on the sample rate. The audio hardware
is responsible for ensuring that the position and sample rate of audio regions match.
This mode is only advisable if you are sure that the Word Clock and time code master
are running in sync—by using an external SMPTE or Word Clock synchronizer, for
example.
• Digital: Similar to External or Free, but the DAE/TDM hardware is also set up to
synchronize to the sample rate of the incoming digital signal.
• SSD/VSD Type: Exactly the same as Digital, but a SMPTE Slave Driver (SSD) or Video
Slave Driver (VSD) is used in addition, to synchronize with the sample and frame rates
used in Logic Pro. (The SMPTE Slave Driver is a device which synchronizes Pro Tools
hardware to incoming time code or Word Clock signals.)
1215 Chapter 43 Project Settings in Logic Pro