Understanding timestamps from tracking plugin

[lillysanchez]

I'm having trouble understand what the timestamps stored alongside the tracking plugin's data mean.

The OpenEphys manual (https://open-ephys.github.io/gui-docs/User-Manual/Recording-data/Binary-format.html) states that the timestamps are 64bit floats as NPY format files. When reading the TTLs using numpy load command (or the open_ephys analysis package) I find that the data are integers.

However, the timestamps from the tracking plugin (contained in a different record node from the TTL timestamps) do not span the same time frame as the TTL. The tracking timestamp interval varies from 77,000 to 336,000, whereas the TTL timestamp intervals are consistently 150 and 220 (for on/off intervals). Again, I don't know what the units are. The TTL could be in ms, but the tracking plugin time can't be in ms or s. If one assumes that the tracking plugin timestamps are in units of the sample rate (30kHz), the total time still doesn't make sense interpreting as µs, ms, or s (it is 25,850).

I'd like to use the tracking plugin. The reason I'm not using Bonsai to track the position of the animal is that I don't think it can be synced with the TTL as that signal is going straight to BNC connector board attached to the open ephys acquisition system. Thus, finding the position of the animal will always be difficult as the bonsai tracking and open ephys electrophysiology recording won't start at the same time.

Does the data need to be scaled by the sample rate to get the time (in seconds)? If I do that, the TTL elapsed time is reasonable for how long I ran the test recording.