NsxFile.getdata() returns only the first segment for a multi-segment .ns3 file

[Zippereden]

Summary

NsxFile.getdata() returns only the first segment from a .ns3 file that contains three segments according to MATLAB NPMK openNSx(..., 'noread').

This may cause underestimation of recording duration and incorrect NSx/NEV timestamp alignment.

File information

• File type: .ns3
• Sampling frequency: 2000 Hz
• Number of channels: 128

Python / brpylib

# Python: 3.10.20
# NumPy: 1.26.4
# brpylib version: 2.0.3
from brpylib import NsxFile

nsx = NsxFile(r"path/to/file.ns3")
data = nsx.getdata()

print(len(data["data"]))
print(data["data"][0].shape)
print(data["data_headers"])

nsx.close()

output:

1
(128, 222453)
[{'Timestamp': 102417735, 'NumDataPoints': 222453, 'data_time_s': 111.2265}]

MATLAB / NPMK comparison

Using the same file:

nsx = openNSx('path/to/file.ns3', 'noread');

disp(nsx.MetaTags.Timestamp(:))
disp(nsx.MetaTags.DataPoints(:))

Output:

Timestamp:
102417735
105754560
155579445

DataPoints:
222453
3321658
170053

Question

Is NsxFile.getdata() expected to support multi-segment / multi-data-packet NSx files? If yes, this appears to be a parsing bug. If not, it may be useful to document this limitation explicitly.