7.14. ioctl VIDIOC_ENUM_FMT¶
7.14.1. Name¶
VIDIOC_ENUM_FMT - Enumerate image formats
7.14.2. Synopsis¶
-
int
ioctl
(int fd, VIDIOC_ENUM_FMT, struct v4l2_fmtdesc *argp)¶
7.14.3. Arguments¶
fd
- File descriptor returned by open().
argp
- Pointer to struct
v4l2_fmtdesc
.
7.14.4. Description¶
To enumerate image formats applications initialize the type
and
index
field of struct v4l2_fmtdesc
and call
the ioctl VIDIOC_ENUM_FMT ioctl with a pointer to this structure. Drivers
fill the rest of the structure or return an EINVAL
error code. All
formats are enumerable by beginning at index zero and incrementing by
one until EINVAL
is returned.
Note
After switching input or output the list of enumerated image formats may be different.
-
v4l2_fmtdesc
¶
__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 v4l2_buf_type . |
__u32 | flags |
See Image Format Description Flags |
__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: |
Several image formats are already defined by this specification in Image Formats. Attention 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. |
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. |
7.14.5. 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.
- EINVAL
- The struct
v4l2_fmtdesc
type
is not supported or theindex
is out of bounds.