Two methods I can think of off the top of my head. I'm not really sure which one is better (it might depend on what you're doing exactly):
1) filesystem::g_is_remote_or_unrecognized() will return true for "cdda://" locations....but it will also return true for "http://" and others....
2) Is there anything wrong with using this?
CODE
(strcmp_partial(file_path, "cdda://")==0)