ioctl VIDIOC_ENUM_FMT
&manvol;

# VIDIOC_ENUM_FMT

Enumerate image formats

    	int ioctl
    	int fd
    	int request
    	struct v4l2_fmtdesc
    *argp

## Arguments

`fd`

  &fd;

`request`

  VIDIOC_ENUM_FMT

`argp`

## Description

To enumerate image formats applications initialize the type and index field of &v4l2-fmtdesc; and call the `VIDIOC_ENUM_FMT` ioctl with a pointer to this structure. Drivers fill the rest of the structure or return an &EINVAL;. All formats are enumerable by beginning at index zero and incrementing by one until EINVAL is returned.

Note that after switching input or output the list of enumerated image formats may be different.

### struct v4l2_fmtdesc

&cs-str;
__u32 | index | Number of the format in the enumeration, set by the application. This is in no way related to the pixelformat field.
__u32 | type | Type of the data stream, set by the application. Only these types are valid here: `V4L2_BUF_TYPE_VIDEO_CAPTURE`, `V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE`, `V4L2_BUF_TYPE_VIDEO_OUTPUT`, `V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE` and `V4L2_BUF_TYPE_VIDEO_OVERLAY`. See .
__u32 | flags | See
__u8 | description[32] | Description of the format, a NUL-terminated ASCII string. This information is intended for the user, for example: "YUV 4:2:2".
__u32 | pixelformat | The image format identifier. This is a four character code as computed by the v4l2_fourcc() macro:

    #define v4l2_fourcc(a,b,c,d) (((__u32)(a)<<0)|((__u32)(b)<<8)|((__u32)(c)<<16)|((__u32)(d)<<24))

Several image formats are already defined by this specification in . Note these codes are not the same as those used in the Windows world.

__u32 | reserved[4] | Reserved for future extensions. Drivers must set the array to zero.

### Image Format Description Flags

&cs-def;
`V4L2_FMT_FLAG_COMPRESSED` | 0x0001 | This is a compressed format.
`V4L2_FMT_FLAG_EMULATED` | 0x0002 | This format is not native to the device but emulated through software (usually libv4l2), where possible try to use a native format instead for better performance.

&return-value;

EINVAL

  The &v4l2-fmtdesc; type is not supported or the index is out of bounds.