`__match_events__` matches rising edges (positive) with falling edges (negative)

[f-dy]

In the current version of the code, each flash generates two events:

• one for the rising edge (positive=True)
• one for the falling edge (positive=False)

However, the event matching code ignores this, and matches each event with any event in the other cameras, even if they don't have the same value for "positive". This may lead to wrong synchronization, with the beginning of flashes in one camera being matched to the end of flashes in another camera.