Super, vielen Dank für den Tipp mit BASS_UNICODE.
So klappt es:
Code:
if (lowerCase(ExtractFileExt(aFilename)) = '.mp3') then
flags := BASS_STREAM_PRESCAN or BASS_UNICODE
else
flags := BASS_UNICODE;
result := BASS_StreamCreateFile(False, PChar(aFilename), 0, 0, flags);