[Eeglablist] importing events from mff files

[Roy Cox]

hi all,

I have a couple of event-related questions about EGI mff data that I'm
hoping to get some community feedback on.

Background: we're trying to import events from EGI mff files. I'm aware of
several eeglab and fieldtrip-related options for importing mff data
(including event markers), but due to data size (~40 GB) we can't easily
import an entire file just to get to the markers. Instead, we're hoping to
just read the marker files and obtain event timing relative to the start of
recording (or in some other understandable way). However, some of our mff
files have data discontinuities (as indicated by multiple "epochs" in
epochs.xml), and we're trying to figure out how to handle this.

1) As a prelude, event latencies in eeglab for continuous data are said to
be in sample points (
https://sccn.ucsd.edu/wiki/Chapter_03:_Event_Processing#Event_processing_from_the_Matlab_command_line).
However, when importing events using *pop_importevent*, the *latency* field
is required to be in seconds. So it appears that the term "latency" refers
to (slightly but importantly) different things in different contexts. Is
this correct?

2) Turning to mff: mff event files (Events****.xml) appear to show event
timing in clock time. What is the origin of this clock time? More
importantly, can it (still) be trusted in the context of data
discontinuities? (As a side note, if anyone has any documentation with
details of the mff format, especially event timing, that would be very
welcome.)

3) I've tried using the *mff_importevents *function from the MFFMatlabIO
(v3.4) plugin. While it runs, I can't be sure it's working as intended.
It's unclear a) what the input argument *begTime* is supposed to hold, b)
how returned latencies are represented (seconds, sample points?), c)
whether data discontinuities are accounted for (I suspect not since there
is no reference to the epochs.xml file).

Any and all insights much appreciated.

Roy