mne-tools / mne-tools/mne-python
Bad split size with raw.save
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Description
In today's weird bug category, I have a MEGIN recording test_sleep_raw.fif splitted in 2 files (2 GB + 1.3 GB). The I/O roundtrip through MNE-Python to crop the 40 first second before running MEGIN's MaxFilter yields 2 files (so far so good), of size 2.1 GB + 1.2 GB, despite the default split_size='2GB' argument.
from mne.io import read_raw_fif
raw = read_raw_fif("test_sleep_raw.fif", preload=True)
raw.del_proj(len(raw.info["projs"]) - 1)
raw.crop(40, None)
raw.save("test_sleep_cropped_raw.fif", drop_small_buffer=True)
And MaxFilter doesn't like that 2 145 MB size of the first file 😢
ERROR: Too large output file (2145 MB)!
Tested on MNE-main.
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Research direction
Start with the read_raw_fif and raw.save calls in the reproduction, focusing on the default split_size='2GB' behavior and drop_small_buffer=True. Reproduce the crop-and-save round trip with the provided snippet, then verify that the generated files stay within the expected size and are accepted by MaxFilter.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- data
- Issue type
- Bug
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 45/100