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ioctl VIDIOC_ENUM_FRAMESIZES

Name

VIDIOC_ENUM_FRAMESIZES -- Enumerate frame sizes

Synopsis

int ioctl(int fd, int request, struct v4l2_frmsizeenum *argp);

Arguments

fd

File descriptor returned by open().

request

VIDIOC_ENUM_FRAMESIZES

argp

Pointer to a struct v4l2_frmsizeenum that contains an index and pixel format and receives a frame width and height.

Description

Experimental: This is an experimental interface and may change in the future.

This ioctl allows applications to enumerate all frame sizes (i. e. width and height in pixels) that the device supports for the given pixel format.

The supported pixel formats can be obtained by using the VIDIOC_ENUM_FMT function.

The return value and the content of the v4l2_frmsizeenum.type field depend on the type of frame sizes the device supports. Here are the semantics of the function for the different cases:

When the application calls the function with index zero, it must check the type field to determine the type of frame size enumeration the device supports. Only for the V4L2_FRMSIZE_TYPE_DISCRETE type does it make sense to increase the index value to receive more frame sizes.

Note that the order in which the frame sizes are returned has no special meaning. In particular does it not say anything about potential default format sizes.

Applications can assume that the enumeration data does not change without any interaction from the application itself. This means that the enumeration data is consistent if the application does not perform any other ioctl calls while it runs the frame size enumeration.

Structs

In the structs below, IN denotes a value that has to be filled in by the application, OUT denotes values that the driver fills in. The application should zero out all members except for the IN fields.

Table 1. struct v4l2_frmsize_discrete

__u32widthWidth of the frame [pixel].
__u32heightHeight of the frame [pixel].

Table 2. struct v4l2_frmsize_stepwise

__u32min_widthMinimum frame width [pixel].
__u32max_widthMaximum frame width [pixel].
__u32step_widthFrame width step size [pixel].
__u32min_heightMinimum frame height [pixel].
__u32max_heightMaximum frame height [pixel].
__u32step_heightFrame height step size [pixel].

Table 3. struct v4l2_frmsizeenum

__u32index IN: Index of the given frame size in the enumeration.
__u32pixel_format IN: Pixel format for which the frame sizes are enumerated.
__u32type OUT: Frame size type the device supports.
union  OUT: Frame size with the given index.
 struct v4l2_frmsize_discretediscrete 
 struct v4l2_frmsize_stepwisestepwise 
__u32reserved[2] Reserved space for future use.

Enums

Table 4. enum v4l2_frmsizetypes

V4L2_FRMSIZE_TYPE_DISCRETE1Discrete frame size.
V4L2_FRMSIZE_TYPE_CONTINUOUS2Continuous frame size.
V4L2_FRMSIZE_TYPE_STEPWISE3Step-wise defined frame size.

Return Value

On success 0 is returned, on error -1 and the errno variable is set appropriately:

See the description section above for a list of return values that errno can have.