Measuring Beat Clock Latency

To determine the correct MIDI Beat Clock offset for an external MIDI device:

1 Ensure that your computer and external MIDI device are correctly connected and configured for MIDI, and that its audio output is correctly connected to audio inputs on your Pro Tools audio interface.

2 Ensure that your external MIDI device is configured to receive MIDI Beat Clock, and that it is correctly configured to play back a simple rhythmic pattern “on the beat.”

3 Create a new Pro Tools session.

4 In the MIDI Beat Clock dialog, ensure that MIDI Beat Clock is enabled and that the device is selected.

5 Set the Main Time Scale to Bars|Beats.

6 Create a new audio track and select the audio input channels for your external MIDI device.

7 Record enable the audio track and start recording. MIDI Beat Clock is sent to the external MIDI device, which starts playing back the pattern.

8 Stop recording after a few bars.

9 Enable both Snap to Grid and Show Grid.

10 With the Selector tool, place the edit cursor on the beat grid prior to a prominent transient in the waveform that is “on the beat.”

11 Enable Tab to Transients and Shift+Tab to the transient. The duration of this selection is the approximate amount of latency for your external MIDI device.

 

Measuring the offset for MIDI Beat Clock in samples

12 Switch the Main Time Scale to Samples. The length of the selected clip in samples is the MIDI Beat Clock latency for that device.

13 In the MIDI Beat Clock dialog, enter the Sample 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 different 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.