Anyways, thanks, I'll look at the callback functions later on. Although I think the original reason why I didn't use them was because they didn't support multichannel re-multiplexing. I'll look again.
What needs to be done to add unicode support for Windows?
The other alternative is to keep everything in UTF8 and do all the conversions at the last second.See https://trac.xiph.org/ticket/268 for the vorbisenc patch set.
Support committed in http://git.xiph.org/?p=opusfile.git;a=comm...;h=f65dab6f653a.
Would it be safe to assume that if this gets implemented in the next compiled and official release of the libopusfile library that all I will need to do is to convert the filename by a call to ::WideCharToMultiByte(CP_UTF8,...)?
Me personally, as an active Windows developer, I would prefer a separate op_open_fileW (while retaining the above changed functionality on the original op_open_file function)