LFP Viewer plot discontinuity at low sampling rates

[florin-pop]

Hello,
I've recently started working on a plugin for open-ephys and I noticed a strange behaviour with signals that have a low sampling rate (around 100Hz), specifically there are discontinuities in the waveform.
The behaviour can be reproduced with the File Reader by loading this sample data which contains 472 samples and 4 channels, each sample has a constant value (0.97uV for channel 1, approx. 2 uV for channel 2 and so on). The expectation is to see a continuous line in the LFP plot, but it's often an interrupted line.

This behaviour is accentuated for more complex signals and they look broken. When the sampling rate is 1kHz or higher I didn't notice the any issues.
I was trying to investigate if I am doing something wrong and started the GUI with the debugger and noticed some assertions failing in a buffer associated with LFP. Could this be a limitation or a bug with open-ephys?

[jsiegle]

It looks like adding a continue statement after updating lastIndex avoids the assertion and fixes the display glitch:

plugin-GUI/Plugins/LfpDisplayNode/LfpDisplayCanvas.cpp

Lines 1231 to 1235 in 8a18e3a

	if (lastIndex < 0)
	{
	lastIndex = displayBufferSize;
	continue;
	}

If that works on your end, we will include this change in the next release!

[florin-pop]

@jsiegle thank you for looking into this. I can confirm that your suggestion does indeed fix the problem. I also tested it with a heartbeat stream and it worked well. This issue can be closed.