File descriptor returned by
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.
On success 0 is returned, on error -1 and the
errno variable is set appropriately:
This ioctl is not supported.