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labstreaminglayer / App-BioSemi

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Signal delays in analog input box w.r.t. digital trigger #2

Open cll008 opened 5 years ago

cll008 commented 5 years ago

I'm currently investigating a timing issue where a square wave is 2-3 frames delayed (2048 Hz, approx. 1 - 1.4 ms) when recorded via the analog input box and compared against the digital trigger. I replicated the experiment (and used EEGLAB for data processing) on a .bdf file from ActiView, and the square waves from both the analog and digital signals are exactly aligned.

tstenner commented 5 years ago

What's the native sampling rate?

512 commented 5 years ago

okay

cll008 commented 5 years ago

The speed mode of the amp is set to acquire at 2048 Hz and the "Resample to 512Hz" in App is checked for the recording.

cll008 commented 5 years ago

The original recordings were actually done at 2048 Hz. I tried again with a recording at 512 Hz: now the distribution of delays is most concentrated at 1 sample (2 ms), with some at 0 sample and outliers at 2 samples.

mlemma44 commented 3 years ago

The original recordings were actually done at 2048 Hz. I tried again with a recording at 512 Hz: now the distribution of delays is most concentrated at 1 sample (2 ms), with some at 0 sample and outliers at 2 samples.

I am running similar tests and and am also seeing that the signal from the Analog Input Box (AIB) is 1 sample earlier than the same signal from the AD box.