Apple Logic Express 7 - Manual (Page 455)

Chapter 18 Synchronization 455
Validate MTC
This pull-down menu option allows you to specify how often Logic checks for incoming
time code, in order to ensure synchronization. In general, you should leave this option
set to always. There are some devices, however, that generate timecode pulses that
may require a specific number of frames to be set, in order to maintain synchronization.
The never, Jam Sync option basically sets Logic to “free-wheel” if synchronization is lost.
In other words, Logic will run on its own internal clock (at the most recently received
tempo) if the synchronization pulse is lost. This approach ensures that recording will
continue, even if the incoming timing pulse fails.
SMPTE Offset
This is where you set the SMPTE offset for the song. As songs don’t always need to start
precisely at bar 1, you can select any bar position to be played at the set SMPTE time.
The preset is 1/1/1/1 at 1:00:00:00. The SMPTE offset 1:00:00:00 is normally used,
because it allows you to pre-roll an amount of time code.
Audio
MTC [fps]
This display shows the deviation between the incoming MTC, and its nominal frame
rate.
If the deviation is too large, please make sure that you have set the right frame rate (on
the General page of the synchronization window). If in doubt, set the frame rate to
24 fps and switch on Auto detect format of MTC.
If the frame rate is correct, you can use this display to adjust the tape speed of the
master machine to the nominal value (the same speed used when the time code was
recorded). Adjust the varipitch control on the master machine, until the vertical yellow
line is centered.
Sample Rate (Hz)
This display shows the deviation of the sample rate from its nominal value.
Bear in mind that some audio hardware will not allow any variation in the sample rate.
Deviation (ms)
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 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. 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.