parkslab / labstreaminglayer

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pop_loadxdf introduces datashifts for irregular sampling rate #9

Open GoogleCodeExporter opened 8 years ago

GoogleCodeExporter commented 8 years ago
What steps will reproduce the problem?
1. importing data with pop_loadxdf introduces data shifts releative to marker 
channel for EEG streams with irregular sampling rate
2.
3.

What is the expected output? What do you see instead?
EEG events should follow a given marker at a fixed delay (e.g. N1). Instead the 
delay between marker onset and EEG response increases over time. 

What version of the product are you using? On what operating system?
The amplifiers we used have a nominal sampling rate of 500. The effective 
sampling rates are 499.83 and 500.6. 

Please provide any additional information below.
The problem arises when importing data into EEG lab. pop_loadxdf calls 
eeg_load_xdf using the nominal_srate by default. This leads to shifts in the 
data relative to the marker. If effective-srate< nominal_srate this shift is 
negative otherwise positive. 

using the effective_rate in eeg_load_xdf instead solves the problem in my case. 

Original issue reported on code.google.com by bleichne...@gmail.com on 10 Feb 2014 at 2:05