internal MidiDeviceInfo(int id, IntPtr ptr)
 {
     ID = id;
     this.info = (PmDeviceInfo) Marshal.PtrToStructure (ptr, typeof (PmDeviceInfo));
 }
 internal MidiDeviceInfo(int id, IntPtr ptr)
 {
     this.id   = id;
     this.info = (PmDeviceInfo)Marshal.PtrToStructure(ptr, typeof(PmDeviceInfo));
 }