def nframes(self):
        """Gets the number of frames in the source file."""
        length = ctypes.c_long()
        size = ctypes.c_int(ctypes.sizeof(length))
        check(_coreaudio.ExtAudioFileGetProperty(
            self._obj, PROP_LENGTH, ctypes.byref(size), ctypes.byref(length)
        ))
        return length.value
Gets the number of frames in the source file.