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@skjerns
Last active October 20, 2024 03:09
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Save a mne.io.Raw object to EDF/EDF+/BDF/BDF+
# -*- coding: utf-8 -*-
"""
Created on Wed Dec 5 12:56:31 2018
@author: skjerns
Gist to save a mne.io.Raw object to an EDF file using pyEDFlib
(https://github.com/holgern/pyedflib)
Disclaimer:
- Saving your data this way will result in slight
loss of precision (magnitude +-1e-09).
- It is assumed that the data is presented in Volt (V),
it will be internally converted to microvolt
- BDF or EDF+ is selected based on the filename extension
- Annotations preserved
Update: Since 2021, MNE also supports exporting EDF via edfio:
https://mne.tools/stable/generated/mne.export.export_raw.html
"""
import pyedflib # pip install pyedflib
from pyedflib import highlevel # new high-level interface
from pyedflib import FILETYPE_BDF, FILETYPE_BDFPLUS, FILETYPE_EDF, FILETYPE_EDFPLUS
from datetime import datetime, timezone, timedelta
import mne
import os
def _stamp_to_dt(utc_stamp):
"""Convert timestamp to datetime object in Windows-friendly way."""
if 'datetime' in str(type(utc_stamp)): return utc_stamp
# The min on windows is 86400
stamp = [int(s) for s in utc_stamp]
if len(stamp) == 1: # In case there is no microseconds information
stamp.append(0)
return (datetime.fromtimestamp(0, tz=timezone.utc) +
timedelta(0, stamp[0], stamp[1])) # day, sec, μs
def write_mne_edf(mne_raw, fname, picks=None, tmin=0, tmax=None,
overwrite=False):
"""
Saves the raw content of an MNE.io.Raw and its subclasses to
a file using the EDF+/BDF filetype
pyEDFlib is used to save the raw contents of the RawArray to disk
Parameters
update 2021: edf export is now also supported in MNE:
https://mne.tools/stable/generated/mne.export.export_raw.html
----------
mne_raw : mne.io.Raw
An object with super class mne.io.Raw that contains the data
to save
fname : string
File name of the new dataset. This has to be a new filename
unless data have been preloaded. Filenames should end with .edf
picks : array-like of int | None
Indices of channels to include. If None all channels are kept.
tmin : float | None
Time in seconds of first sample to save. If None first sample
is used.
tmax : float | None
Time in seconds of last sample to save. If None last sample
is used.
overwrite : bool
If True, the destination file (if it exists) will be overwritten.
If False (default), an error will be raised if the file exists.
"""
print('did you know EDF export is now supported in MNE via edfio? have a look at https://mne.tools/stable/generated/mne.export.export_raw.html')
if not issubclass(type(mne_raw), mne.io.BaseRaw):
raise TypeError('Must be mne.io.Raw type')
if not overwrite and os.path.exists(fname):
raise OSError('File already exists. No overwrite.')
# static settings
has_annotations = True if len(mne_raw.annotations)>0 else False
if os.path.splitext(fname)[-1] == '.edf':
file_type = FILETYPE_EDFPLUS if has_annotations else FILETYPE_EDF
dmin, dmax = -32768, 32767
else:
file_type = FILETYPE_BDFPLUS if has_annotations else FILETYPE_BDF
dmin, dmax = -8388608, 8388607
print('saving to {}, filetype {}'.format(fname, file_type))
sfreq = mne_raw.info['sfreq']
date = _stamp_to_dt(mne_raw.info['meas_date'])
if tmin:
date += timedelta(seconds=tmin)
# no conversion necessary, as pyedflib can handle datetime.
#date = date.strftime('%d %b %Y %H:%M:%S')
first_sample = int(sfreq*tmin)
last_sample = int(sfreq*tmax) if tmax is not None else None
# convert data
channels = mne_raw.get_data(picks,
start = first_sample,
stop = last_sample)
# convert to microvolts to scale up precision
channels *= 1e6
# set conversion parameters
n_channels = len(channels)
# create channel from this
try:
f = pyedflib.EdfWriter(fname,
n_channels=n_channels,
file_type=file_type)
channel_info = []
ch_idx = range(n_channels) if picks is None else picks
keys = list(mne_raw._orig_units.keys())
for i in ch_idx:
try:
ch_dict = {'label': mne_raw.ch_names[i],
'dimension': mne_raw._orig_units[keys[i]],
'sample_rate': mne_raw._raw_extras[0]['n_samps'][i],
'physical_min': mne_raw._raw_extras[0]['physical_min'][i],
'physical_max': mne_raw._raw_extras[0]['physical_max'][i],
'digital_min': mne_raw._raw_extras[0]['digital_min'][i],
'digital_max': mne_raw._raw_extras[0]['digital_max'][i],
'transducer': '',
'prefilter': ''}
except:
ch_dict = {'label': mne_raw.ch_names[i],
'dimension': mne_raw._orig_units[keys[i]],
'sample_rate': sfreq,
'physical_min': channels.min(),
'physical_max': channels.max(),
'digital_min': dmin,
'digital_max': dmax,
'transducer': '',
'prefilter': ''}
channel_info.append(ch_dict)
f.setPatientCode(mne_raw._raw_extras[0]['subject_info'].get('id', '0'))
f.setPatientName(mne_raw._raw_extras[0]['subject_info'].get('name', 'noname'))
f.setTechnician('mne-gist-save-edf-skjerns')
f.setSignalHeaders(channel_info)
f.setStartdatetime(date)
f.writeSamples(channels)
for annotation in mne_raw.annotations:
onset = annotation['onset']
duration = annotation['duration']
description = annotation['description']
f.writeAnnotation(onset, duration, description)
except Exception as e:
raise e
finally:
f.close()
return True
@alexrockhill
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alexrockhill commented Jun 30, 2020

@skjerns ahh, I see. Maybe worth thinking about whether this could be in mne-bids since there is already a pybv dependency. That does seem like when the data needs to be in edf, i.e. when it's in BIDS. @jasmainak what do you think?

Also, the gist is nice, thanks for doing that but it is a rather important part that can go very wrong if the file is exported incorrectly and it would be great to have some round trip tests that would be added if it were to be a PR.

@jasmainak
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I'm a bit hesitant to take on the responsibility of an edf writer. There are tons of corner cases in the edf format. Why not contribute to existing efforts such as pyedf: https://github.com/bids-standard/pyedf

@alexrockhill
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That doesn't have any tests either haha

It seems like there is a lot of use of the gist and like people would probably like it to be officially supported by mne and @skjerns said he would write the initial PR but I understand the hesitance and I get the message. I thought it was worth floating the idea.

@datalw
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datalw commented Aug 21, 2020

Hi,
this gist is really great idea! Just the functionality, which I have been searched in mne and did not find. A great supplement. Big thanks to you!

I tried to save the preprocessed mne raw object into a new edf, and got the following error
...

line 27, in _stamp_to_dt
    stamp = [int(s) for s in utc_stamp]
TypeError: 'datetime.datetime' object is not iterable

raw.info['meas_date'] in my script gives me:

datetime.datetime(2020, 3, 12, 16, 34, 55, tzinfo=datetime.timezone.utc)

Have you encoutered this problem?

@LunaHub
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LunaHub commented Aug 21, 2020

Yes, I had the same problem. I solved it by changing line 76 to date = mne_raw.info['meas_date']. However then I got a new problem and I actually gave up :P Let me know if you succed!

@skjerns
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skjerns commented Aug 21, 2020

I've adapted the script.

@datalw can you check if it works now?

@datalw
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datalw commented Aug 21, 2020

@skjerns Thanks a lot for the swift response! I tried the adapted version and got the following error:

----> 3     if 'datetime' in type(utc_stamp): return utc_stamp
      4     # The min on windows is 86400
      5     stamp = [int(s) for s in utc_stamp]

TypeError: argument of type 'type' is not iterable

So I changed if 'datetime' in type(utc_stamp): to if 'datetime' in str(type(utc_stamp)) and it works :D Would you mind to adapt it again?
Thanks a lot for the great work!
@LunaHub it works for me so far, you could try it again : )

@skjerns
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skjerns commented Aug 21, 2020

oops, yes didnt test it, thank's, I corrected it

@datalw
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datalw commented Sep 14, 2020

I have used the gist for a while, it is really awesome, especially for saving the preprocessed data!

I am here again for a follow-up question. So far the files without annotations have been saved successfully. However for a file with annotations, the raw.times in the saved file was incorrect. I have looked into the code and found out the problem might be due to this line
'sample_rate': mne_raw._raw_extras[0]['n_samps'][i]

mne_raw.info['sfreq'] gives 256, but mne_raw._raw_extras[0]['n_samps'][i] gives 2048 instead.
Since I have never dealt with _raw_extras, I tried to find some information about _raw_extras in mne documention, but failed.

Does anyone know how to solve this problem, or how I can proceed? Or is this a bug in _raw_extras?

@alexrockhill
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alexrockhill commented Sep 14, 2020

I am not familiar with raw._raw_extras you might be able to reach a wider audience that wrote that part of the code on Gitter unless someone on this thread knows https://gitter.im/mne-tools/mne-python

@skjerns
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skjerns commented Sep 16, 2020

@datalw did you resample the data? was one of original sample frequencies 2048?

to be honest, I just hacked this snippet together and changed it often over time, I'm also not very familiar with the mne internals. If you find a solution, let me know! I'm still in favor of integrating edf writing compatibility inside mne, but currently they don't want to introduce optional dependencies. maybe that changes as a python-native implementation of edflib has been published last month :)

@nateGeorge
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So this still isn't incorporated into mne-python, any chance it ever will? Been a few years.

@skjerns
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skjerns commented Sep 28, 2020

Feel free to ask this directly at MNE: https://github.com/mne-tools/mne-python/issues or the gitter https://gitter.im/mne-tools/mne-python

The problem was the additional dependency on pyedflib and that pyedflib uses Cython to compile some C libraries, which they did not want to include (afaik, and which I somehow understand).

However, we could ask if it would be possible to include an optional dependency on pyedflib. Additionally, EDDlib has just released a Python-only-version which would solve some problems :) but its quite slow (it's Python, nevertheless)

@datalw
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datalw commented Sep 28, 2020

@alexrockhill @skjerns Thanks a lot for the reply and sorry for my delayed answer. I plan to come back to this issue in the next couple of weeks and if I find a solution I will let you @skjerns know ; )

@bonniekcn
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Hello, thanks a lot for the great work! I am having one problem when using this script. When I try to open the resulted edf file this message came up "Error, number of datarecords is 0, expected >0. You can fix this problem with the header editor, check the manual for details. File is not a valid EDF or BDF file.". I am not quite sure why is this the case and I wonder if anyone is having the same problem or has any solution.

Thanks a lot!

@alexrockhill
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That's a bit hard to diagnose what's going on without sharing a minimally reproducible example that someone else can run on their machine.

It sounds like maybe your mne.io.Raw object didn't have any data in it or any data of type eeg, grad, mag or seeg. See https://mne.tools/stable/generated/mne.io.Raw.html#mne.io.Raw.set_channel_types.

@bonniekcn
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That's a bit hard to diagnose what's going on without sharing a minimally reproducible example that someone else can run on their machine.

It sounds like maybe your mne.io.Raw object didn't have any data in it or any data of type eeg, grad, mag or seeg. See https://mne.tools/stable/generated/mne.io.Raw.html#mne.io.Raw.set_channel_types.

@alexrockhill Hello, thanks a lot for the reply. This is the piece of code I used when creating the mne.io.Raw object.
sample_data_raw_file = os.path.join("filename.edf")
raw = mne.io.read_raw_edf(sample_data_raw_file)
My original document is already in .edf, I put the file through some processing in mne-python and I would want to save the end-product as .edf using your script. Thanks a lot for your help!

@alexrockhill
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alexrockhill commented Oct 16, 2020

From my experience reading in edf files, often the data types are not correctly set by mne by default. I would try setting all your channel types to eeg I assume but whatever type they are and saving again. I'd be interested to know if that works.

Also, I helped a bit but the thanks definitely goes to @skjerns for this gist.

Maybe this will help

import mne
raw_fname = 'filename.edf'
raw = mne.io.read_raw_edf(raw_fname)
raw = raw.set_channel_types({ch: 'eeg' for ch in raw.ch_names})

@bonniekcn
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@alexrockhill
Thanks for the reply. I have tried setting the channel types to eeg using raw = raw.set_channel_types({ch: 'eeg' for ch in raw.ch_names}) , but the resulting file still can't be opened.

@brainhong913
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I am having the same. My guess is that there is some unexpected bug occurs while you reading the raw data from edf. Is there any method to sure I read the edf correctly?

@alexrockhill
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Ok, that was just an informed guess but I couldn't tell you what's wrong because I don't have access to your data.

@bonniekcn
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I realized that the smaller the original file I use the smaller the resulting file that is saved. But nomatter how big my original file is, the resulting file is always too small to be opened. When I called the function I called it this way write_mne_edf(raw,'testfile.edf', overwrite=True). I wonder if I am not aware of some details from the script resulting in this error of getting an extremely small file.

@skjerns
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skjerns commented Oct 20, 2020

It is difficult to help you without having the original file to work with. Feel free to upload the file somewhere (eg wetransfer) and post the link here. Alternatively, if the data is sensitive, send it privately to [email protected]

@bonniekcn
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It is difficult to help you without having the original file to work with. Feel free to upload the file somewhere (eg wetransfer) and post the link here. Alternatively, if the data is sensitive, send it privately to [email protected]

Hello, thank you very much for your reply. I have sent an email to the address provided. Thanks!

@skjerns
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skjerns commented Oct 20, 2020

There was an Exception raised during the file you sent, as the date wasn't set correctly, so the resulting file was just a leftover of an incomplete write. I changed the gist to raise an Exception explicitly and not just print it. It should work now. This was due to a bug in pyedflib, which I fixed now.

@bonniekcn
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There was an Exception raised during the file you sent, as the date wasn't set correctly, so the resulting file was just a leftover of an incomplete write. I changed the gist to raise an Exception explicitly and not just print it. It should work now. This was due to a bug in pyedflib, which I fixed now.

Thank you very much for your help, it works perfectly now!

@raphaelvallat
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Hi @skjerns! Thank you for this great gist, we've been using it a lot in my lab. If the option of integrating it directly into MNE ever comes back to the table (now that there is a native Python implementation), I'd be happy to vouch for it!

Just a quick comment on the code, wouldn't it make more sense to update the date so that it starts at tmin, and not meas_date? Concretely, just adding a timedelta(seconds=tmin) to the date datetime?

Thanks,
Raphael

@skjerns
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skjerns commented Oct 29, 2020

The Python native implementation of edflib is unfortunately extremely slow (I posted a benchmark here), up to 20x slower. So I don't think implementation in mne is going to come soon. But I see what I can do w.r.t this issue, as it seems to be a major feature lacking in mne. It should be possible to speed up quite a bit, with knowing a bit of Python internals and bottlenecks.

good one for the tmin! I'll implement that. I actually never use this gist myself, so I rely on users to improve it :)

@LudovicGardy
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LudovicGardy commented Nov 3, 2020

Hello, and thank you for your great job!

I have a little problem because when I convert a file using your method, it goes from 1h duration to 8h duration (probably related to the sample rate, which is transformed from 2048 to 256Hz somewhere in the process). However, I change absolutely nothing, I just load my .edf data (duration = 1h), use write_edf, load the new .edf data (duration = 8h).

Edit : I solved the problem by changing the following code. Basically I just changed the 'sample_rate' parameter into the ch_dict.

        try:
            ch_dict = {'label': mne_raw.ch_names[i], 
                       'dimension': mne_raw._orig_units[keys[i]], 
                       #'sample_rate': mne_raw._raw_extras[0]['n_samps'][i], 
                       'sample_rate': mne_raw.info["sfreq"],
                       'physical_min': mne_raw._raw_extras[0]['physical_min'][i], 
                       'physical_max': mne_raw._raw_extras[0]['physical_max'][i], 
                       'digital_min':  mne_raw._raw_extras[0]['digital_min'][i], 
                       'digital_max':  mne_raw._raw_extras[0]['digital_max'][i], 
                       'transducer': '', 
                       'prefilter': ''}
        except:
            ch_dict = {'label': mne_raw.ch_names[i], 
                       'dimension': mne_raw._orig_units[keys[i]], 
                       #'sample_rate': sfreq, 
                       'sample_rate': mne_raw.info["sfreq"],
                       'physical_min': channels.min(), 
                       'physical_max': channels.max(), 
                       'digital_min':  dmin, 
                       'digital_max':  dmax, 
                       'transducer': '', 
                       'prefilter': ''}

@bonniekcn
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Hello, thanks a lot for this amazing script. I realize that the resulting file saved from this script will be in the folder which the original data is located. I wonder if there is any way we can change where the output file will be within the script. Thank you.

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