# old versus new event files

**URL:** <https://mne.discourse.group/t/old-versus-new-event-files/1088>\
**Category:** Mailing List Archive (read-only)\
**Tags:** list-archive\
**Created:** [September 19, 2016, 1:09pm UTC](https://mne.discourse.group/t/old-versus-new-event-files/1088 "2016-09-19T13:09:13Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![system](https://global.discourse-cdn.com/free1/uploads/mne/original/1X/85cc6bd2b69cb698a166dc6d880fb550510d0144.jpeg) [@system](https://mne.discourse.group/u/system)\
**Post date:** [September 19, 2016, 1:09pm UTC](https://mne.discourse.group/t/old-versus-new-event-files/1088/1 "2016-09-19T13:09:13Z")

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Hello everyone,

I have a question about the 'old' versus 'new' event (.eve) file formats  
and how those are treated by the mne\_process\_raw function during  
epoching.

In one of my single-trial analyses I had to replace trigger values in  
the raw event files with custom values. I ran those and all seemed well.  
Now I am re-using the same .eve files again and noticed when they are  
read with the mne\_process\_raw I get a warning that these event files are  
detected as 'old format'. This is happening because when replacing the  
triggers I also replaced the trigger value in first line of the event  
file (which is meant to be 0) to some non-sense value (7777 - as for all  
events of no interest). The first line of the event file encodes the  
first pseudo event and the timing in this line and the sample number are  
critical so if I replace these, all subsequent epochs will be  
misaligned. But I didn't change these - just the value of the digital  
trigger channel (i.e. ,the \<to\> value).

MNE manual (I am using 2.7.3 version), however, warns not to touch this  
first line at all. As this line helps the software to interpret the file  
format ('old' vs 'new'). But I can't find anywhere what this actually  
means and how would the epochs be treated in the old format? I only know  
that in the old format .eve file did't have this first empty event. But  
new mne is backward compatible and deals with this somehow.

So I ran with both 'old' (with 7777 non-sense trigger in the 1st line)  
and 'new' (the same but with correct 0 trigger value) event files,  
looked at the single trial epochs and they are identical (I get a matrix  
of 0s when i subtract one from the other). So the question is - does the  
trigger value of the first line matter then? Or would both 'old' and  
'new' versions of the event file be treated in the same way - i.e the  
value of the first sample in the first line be subtracted from the  
subsequent epochs?

Thanks,  
Ana