So far I have found out OMF is from Avid.That's a good start.
But it's old and in its official form only supports 16 bits, probably why I got that "converting sample rate" message.
Many implemetations bend the rules apparently, which leads to incompatibilities.
There is also an OMF2, but I am struggling to find solid information about what is supported by either 1 or 2.
i also read OMF is an API, not a format as such.