LSL timestamps "jump" backward and forward

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Assessment

Difficulty
5/5
Estimated time
Over a week
Newbie friendliness
20/100
Issue type
Bug
Clarity
Needs clarification
Activity status
Stale

Research direction

No source file, test, or entry point is identified in the issue. Start by comparing the EEG and gaze timestamp plots and recording conditions, then trace how LSL timestamps are produced and consumed; done requires identifying the cause of the jumps and documenting or implementing a verified resolution.

Written by the indexing model from the issue text.

Description

I used LSL to record EEG data from a LiveAmp 64 EEG device (Brain Products) and gaze data from a Pupil Labs Neon eye tracker for my study. While reviewing the LSL timestamps, I discovered that in a few of the EEG recordings, the timestamps unexpectedly jumped backward. As a result, all subsequent data points were shifted accordingly. This issue is illustrated in the following figure, where the x-axis represents the sample number and the y-axis shows the corresponding LSL timestamps.

Image

Interestingly, at the same moment when the EEG timestamps jumped backward, the gaze data timestamps showed a forward jump. See figure here:

Image

We were wondering whether this issue was caused by samples being recorded out of order and needing to be resorted, or if the timestamps themselves became incorrect from that point onward.
Has anyone encountered this issue before, or does anyone know what might cause it and how to resolve it?

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