DigiDesign Pro Tools 8.0 Reference Manual page 362

Set the Main Time Scale to Bars|Beats.
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Create a new audio track and select the audio
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input channels for your external MIDI device.
Record enable the audio track and start record-
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ing. MIDI Beat Clock is sent to the external MIDI
device, which starts playing back the pattern.
Stop recording after a few bars.
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Enable both Snap to Grid and Show Grid.
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With the Selector tool, place the edit cursor
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on the beat grid prior to a prominent transient
in the waveform that is "on the beat."
Enable Tab to Transients and Shift+Tab to the
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transient. The duration of this selection is the
approximate amount of latency for your exter-
nal MIDI device (see Figure 19 below).
Figure 19. Measuring the offset for MIDI Beat Clock in samples
344 Pro Tools Reference Guide
Switch the Main Time Scale to Samples. The
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length of the selected region in samples is the
MIDI Beat Clock latency for that device.
In the MIDI Beat Clock dialog, enter the Sam-
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ple Offset value as a negative number.
MIDI Beat Clock Sample Offset
Since MIDI is not sample accurate, you may
want to make several measurements at dif-
ferent grid locations and average them to
come up with the best value for the MIDI
Beat Clock Offset.
Once you have measured the latency for
your MIDI Beat Clock-enabled devices, be
sure to keep a record of these values in case
you need to re-enter the MIDI Beat Clock
Sample Offset in other sessions.