7.55.1. Name

VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL - Enumerate frame intervals

7.55.2. Synopsis

int ioctl(int fd, VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL, struct v4l2_subdev_frame_interval_enum * argp)

7.55.3. Arguments

File descriptor returned by open().
Pointer to struct v4l2_subdev_frame_interval_enum.

7.55.4. Description

This ioctl lets applications enumerate available frame intervals on a given sub-device pad. Frame intervals only makes sense for sub-devices that can control the frame period on their own. This includes, for instance, image sensors and TV tuners.

For the common use case of image sensors, the frame intervals available on the sub-device output pad depend on the frame format and size on the same pad. Applications must thus specify the desired format and size when enumerating frame intervals.

To enumerate frame intervals applications initialize the index, pad, which, code, width and height fields of struct v4l2_subdev_frame_interval_enum and call the ioctl VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL ioctl with a pointer to this structure. Drivers fill the rest of the structure or return an EINVAL error code if one of the input fields is invalid. All frame intervals are enumerable by beginning at index zero and incrementing by one until EINVAL is returned.

Available frame intervals may depend on the current ‘try’ formats at other pads of the sub-device, as well as on the current active links. See ioctl VIDIOC_SUBDEV_G_FMT, VIDIOC_SUBDEV_S_FMT for more information about the try formats.

Sub-devices that support the frame interval enumeration ioctl should implemented it on a single pad only. Its behaviour when supported on multiple pads of the same sub-device is not defined.

struct v4l2_subdev_frame_interval_enum
__u32 index Number of the format in the enumeration, set by the application.
__u32 pad Pad number as reported by the media controller API.
__u32 code The media bus format code, as defined in Media Bus Formats.
__u32 width Frame width, in pixels.
__u32 height Frame height, in pixels.
struct v4l2_fract interval Period, in seconds, between consecutive video frames.
__u32 which Frame intervals to be enumerated, from enum v4l2_subdev_format_whence.
__u32 reserved[8] Reserved for future extensions. Applications and drivers must set the array to zero.

7.55.5. 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.

The struct v4l2_subdev_frame_interval_enum pad references a non-existing pad, one of the code, width or height fields are invalid for the given pad or the index field is out of bounds.