ioctl VIDIOC_QUERYSTD &manvol; VIDIOC_QUERYSTD Sense the video standard received by the current input int ioctl int fd int request v4l2_std_id *argp fd &fd; request VIDIOC_QUERYSTD argp The hardware may be able to detect the current video standard automatically. To do so, applications call VIDIOC_QUERYSTD with a pointer to a &v4l2-std-id; type. The driver stores here a set of candidates, this can be a single flag or a set of supported standards if for example the hardware can only distinguish between 50 and 60 Hz systems. When detection is not possible or fails, the set must contain all standards supported by the current video input or output. &return-value;