Add BrainVision export via pybv

[sappelhoff]

Just announcing that I plan to add export capabilities for BrainVision to the MNE-Python export suite. I thought we had discussed this in other issues already, but I can't find them or they have been closed.

I recently added a feature to pybv to write more complex events, so that mne.Annotations can now be properly written, see: bids-standard/pybv#86

In the future I'd also like to be able to export electrode coordinates ("channel locations"), but I think that can come as an add on slightly later: bids-standard/pybv#44

One feature apart from making this available to MNE-Python users would also be that we can refactor what we currently have in mne-bids: https://github.com/mne-tools/mne-bids/blob/fa7a94bb0ef03691aa881f39c90b23a7aa69a923/mne_bids/write.py#L963

Let me know if you have thoughts on this :-)

[larsoner]

Yes feel free! I think the idea is to have as much export code as possible live in the downstream lib (in this case, pybv), so that the code in MNE-Python is something simple like:

if ext in ('.vhdr', ...):
    pybv = _whatever_our_safe_importer_is('pybv')
    pybv.export_raw(raw)

and then you add pybv to the -testing requirements (and maybe also environment.yml and requirements.yml), and write one small test here in test_export.py or whatever we call it.

[sappelhoff]

Sounds good to me! I'd then keep pybv._export_raw_mne (for example) a private function in pybv 👍

[sappelhoff]

Is there a reason why export_evokeds_mff is in the public API, instead of being private and users getting to it via export_evoked?

[larsoner]

Yes because it has extra options, see discussion in and around #9406 (comment)

[sappelhoff]

Thanks, I was wondering about that, because export_raw also has extra options that are only used for EDF 🤔 is that simply an inconsistency due to the way the module recently "grew"?

[larsoner]

Can't recall if it was intentional or not, but it would be nice to be consistent