def _set_framerate_delta(self, value):
    self._check_camera_open()
    if (self.framerate == 0):
        raise PiCameraValueError('framerate_delta cannot be used with framerate_range')
    value = mo.to_fraction((self.framerate + value), den_limit=256)
    self._camera.outputs[self.CAMERA_PREVIEW_PORT].params[mmal.MMAL_PARAMETER_FRAME_RATE] = value
    self._camera.outputs[self.CAMERA_VIDEO_PORT].params[mmal.MMAL_PARAMETER_FRAME_RATE] = value
def _set_framerate_delta(self, value):
    self._check_camera_open()
    if (self.framerate == 0):
        raise PiCameraValueError('framerate_delta cannot be used with framerate_range')
    value = mo.to_fraction((self.framerate + value), den_limit=256)
    self._camera.outputs[self.CAMERA_PREVIEW_PORT].params[mmal.MMAL_PARAMETER_FRAME_RATE] = value
    self._camera.outputs[self.CAMERA_VIDEO_PORT].params[mmal.MMAL_PARAMETER_FRAME_RATE] = value