Apple Logic Pro 9 - Manual (Page 1214)

• Deviation slider: This display shows the current phase deviation of the Word Clock from
the time code master—in other words, the deviation between audio and MIDI. Varying
time code signals shown in this display indicate how Logic Pro regulates the sample
rate of the hardware when in MTC Continuous sync mode. Even large time code
variations result in no deviation between audio and MIDI synchronization. Your audio
hardware must be capable of continuously variable sample rates for this to function.
Small deviations between audio and MIDI are unavoidable, because MIDI can (and
should) follow the time code master directly.
Note: The real-time sample rate conversion feature of Logic Pro allows it to follow an
external MTC signal (MTC Continuous), while maintaining the correct audio playback
pitch and speed. This feature even works when recording in MTC-slave mode.
Audio Sync Status Settings
• Core Audio pop-up menu: This is where you define how your Core Audio hardware is
synchronized to an external time code master.
• MTC Continuous: Audio regions are started in sync, and the sample rate is continuously
regulated to match variations in the time code master signal. Even very long audio
regions stay in sync in this mode.
• 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.
• DAE/TDM pop-up menu: This is where you define how your DAE or TDM hardware is
synchronized to an external time code master.
• MTC Continuous: Audio regions are started in sync, and the sample rate is continuously
regulated to match variations in the time code master signal. Even very long audio
regions stay in sync in this mode.
1214 Chapter 43 Project Settings in Logic Pro