ioctl VIDIOC_DQEVENT &manvol; VIDIOC_DQEVENT Dequeue event int ioctl int fd int request struct v4l2_event *argp fd &fd; request VIDIOC_DQEVENT argp Dequeue an event from a video device. No input is required for this ioctl. All the fields of the &v4l2-event; structure are filled by the driver. The file handle will also receive exceptions which the application may get by e.g. using the select system call. &cs-str; __u32 type Type of the event. union u &v4l2-event-vsync; vsync Event data for event V4L2_EVENT_VSYNC. &v4l2-event-ctrl; ctrl Event data for event V4L2_EVENT_CTRL. &v4l2-event-frame-sync; frame_sync Event data for event V4L2_EVENT_FRAME_SYNC. &v4l2-event-motion-det; motion_det Event data for event V4L2_EVENT_MOTION_DET. &v4l2-event-src-change; src_change Event data for event V4L2_EVENT_SOURCE_CHANGE. __u8 data[64] Event data. Defined by the event type. The union should be used to define easily accessible type for events. __u32 pending Number of pending events excluding this one. __u32 sequence Event sequence number. The sequence number is incremented for every subscribed event that takes place. If sequence numbers are not contiguous it means that events have been lost. struct timespec timestamp Event timestamp. u32 id The ID associated with the event source. If the event does not have an associated ID (this depends on the event type), then this is 0. __u32 reserved[8] Reserved for future extensions. Drivers must set the array to zero. &cs-str; __u8 field The upcoming field. See &v4l2-field;. &cs-str; __u32 changes A bitmask that tells what has changed. See . __u32 type The type of the control. See &v4l2-ctrl-type;. union (anonymous) __s32 value The 32-bit value of the control for 32-bit control types. This is 0 for string controls since the value of a string cannot be passed using &VIDIOC-DQEVENT;. __s64 value64 The 64-bit value of the control for 64-bit control types. __u32 flags The control flags. See . __s32 minimum The minimum value of the control. See &v4l2-queryctrl;. __s32 maximum The maximum value of the control. See &v4l2-queryctrl;. __s32 step The step value of the control. See &v4l2-queryctrl;. __s32 default_value The default value value of the control. See &v4l2-queryctrl;. &cs-str; __u32 frame_sequence The sequence number of the frame being received. &cs-str; __u32 changes A bitmask that tells what has changed. See . &cs-str; __u32 flags Currently only one flag is available: if V4L2_EVENT_MD_FL_HAVE_FRAME_SEQ is set, then the frame_sequence field is valid, otherwise that field should be ignored. __u32 frame_sequence The sequence number of the frame being received. Only valid if the V4L2_EVENT_MD_FL_HAVE_FRAME_SEQ flag was set. __u32 region_mask The bitmask of the regions that reported motion. There is at least one region. If this field is 0, then no motion was detected at all. If there is no V4L2_CID_DETECT_MD_REGION_GRID control (see ) to assign a different region to each cell in the motion detection grid, then that all cells are automatically assigned to the default region 0. &cs-def; V4L2_EVENT_CTRL_CH_VALUE 0x0001 This control event was triggered because the value of the control changed. Special case: if a button control is pressed, then this event is sent as well, even though there is not explicit value associated with a button control. V4L2_EVENT_CTRL_CH_FLAGS 0x0002 This control event was triggered because the control flags changed. V4L2_EVENT_CTRL_CH_RANGE 0x0004 This control event was triggered because the minimum, maximum, step or the default value of the control changed. &cs-def; V4L2_EVENT_SRC_CH_RESOLUTION 0x0001 This event gets triggered when a resolution change is detected at an input. This can come from an input connector or from a video decoder. &return-value;