static int set_timeperframe(struct v4l2_loopback_device *dev,
		struct v4l2_fract *tpf)
{
        if((tpf->denominator < 1) || (tpf->numerator < 1)) {
	  return -EINVAL;
	}
	dev->capture_param.timeperframe = *tpf;
	dev->frame_jiffies = max(1UL,
		msecs_to_jiffies(1000) * tpf->numerator / tpf->denominator);
	return 0;
}