ioctl VIDIOC_QUERYSTD
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## Name

VIDIOC_QUERYSTD — Sense the video standard received by the current input

## Synopsis

`int ioctl(` | int fd,
| int request,
| v4l2_std_id *argp`)`;

## Arguments

`fd`

  File descriptor returned by `open()`.

`request`

  VIDIOC_QUERYSTD

`argp`

## Description

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. If no signal was detected, then the driver will return V4L2_STD_UNKNOWN. When detection is not possible or fails, the set must contain all standards supported by the current video input or output.

## Return Value

On success 0 is returned, on error -1 and the `errno` variable is set appropriately. The generic error codes are described at the Generic Error Codes chapter.

ENODATA

  Standard video timings are not supported for this input or output.

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