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VIDEO(4)                 BSD Kernel Interfaces Manual                 VIDEO(4)

NAME
     video -- device-independent video driver layer

SYNOPSIS
     video* at uvideo?

     #include <&lt;sys/types.h>&gt;
     #include <&lt;sys/ioctl.h>&gt;
     #include <&lt;sys/videoio.h>&gt;

DESCRIPTION
     The video driver provides support for various video devices.  It provides
     a uniform programming interface layer above different underlying video
     hardware drivers.  The video driver uses the V4L2 (Video for Linux Two)
     API which is widely used by video applications.  Therefore this document
     mainly describes the V4L2 API parts which are supported by the video
     driver.

IOCTLS
     The following ioctl(2) commands are supported:

     VIDIOC_QUERYCAP struct v4l2_capability *
             Query device capabilities.

             struct v4l2_capability {
                     u_int8_t        driver[16];
                     u_int8_t        card[32];
                     u_int8_t        bus_info[32];
                     u_int32_t       version;
                     u_int32_t       capabilities;
                     u_int32_t       reserved[4];
             };

     VIDIOC_ENUM_FMT struct v4l2_fmtdesc *
             Enumerate image formats.

             struct v4l2_fmtdesc {
                     u_int32_t               index;
                     enum v4l2_buf_type      type;
                     u_int32_t               flags;
                     u_int8_t                description[32];
                     u_int32_t               pixelformat;
                     u_int32_t               reserved[4];
             };

     VIDIOC_S_FMT struct v4l2_format *
             Set the data format.

             struct v4l2_format {
                     enum v4l2_buf_type      type;
                     union {
                             struct v4l2_pix_format          pix;
                             struct v4l2_window              win;
                             struct v4l2_vbi_format          vbi;
                             struct v4l2_sliced_vbi_format   sliced;
                             u_int8_t                        raw_data[200];
                     } fmt;
             };

     VIDIOC_G_FMT struct v4l2_format *
             Get the data format.

             Same structure as for VIDIOC_S_FMT.

     VIDIOC_ENUMINPUT struct v4l2_input *
             Enumerate video inputs.

             struct v4l2_input {
                     u_int32_t       index;
                     u_int8_t        name[32];
                     u_int32_t       type;
                     u_int32_t       audioset;
                     u_int32_t       tuner;
                     v4l2_std_id     std;
                     u_int32_t       status;
                     u_int32_t       reserved[32];
             };

     VIDIOC_G_INPUT int *
             Get the current video input.

     VIDIOC_S_INPUT int *
             Select the current video input.

     VIDIOC_REQBUFS struct v4l2_requestbuffers *
             Initiate memory mapping or user pointer I/O.

             struct v4l2_requestbuffers {
                     u_int32_t               count;
                     enum v4l2_buf_type      type;
                     enum v4l2_memory        memory;
                     u_int32_t               reserved[2];
             };

     VIDIOC_QUERYBUF struct v4l2_buffer *
             Query the status of a buffer.

             struct v4l2_buffer {
                     u_int32_t               index;
                     enum v4l2_buf_type      type;
                     u_int32_t               bytesused;
                     u_int32_t               flags;
                     enum v4l2_field         field;
                     struct timeval          timestamp;
                     struct v4l2_timecode    timecode;
                     u_int32_t               sequence;
                     enum v4l2_memory        memory;
                     union {
                             u_int32_t       offset;
                             unsigned long   userptr;
                     } m;
                     u_int32_t               length;
                     u_int32_t               input;
                     u_int32_t               reserved;
             };

     VIDIOC_QBUF struct v4l2_buffer *
             Add a buffer to the queue.

             Same structure as for VIDIOC_QUERYBUF.

     VIDIOC_DQBUF struct v4l2_buffer *
             Remove a buffer from the queue.

             Same structure as for VIDIOC_QUERYBUF.

     VIDIOC_STREAMON int *
             Start video stream.

     VIDIOC_STREAMOFF int *
             Stop video stream.

     VIDIOC_TRY_FMT struct v4l2_format *
             Try a data format.

             Same structure as for VIDIOC_S_FMT.

     VIDIOC_ENUM_FRAMEINTERVALS struct v4l2_frmivalenum *
             Enumerate frame intervals.

             struct v4l2_frmivalemun {
                     u_int32_t               index;
                     u_int32_t               pixel_format;
                     u_int32_t               width;
                     u_int32_t               height;
                     u_int32_t               type;
                     union {
                             struct v4l2_fract               discrete;
                             struct v4l2_frmival_stepwise    stepwise;
                     } un;
                     u_int32_t               reserved[2];
             };

             struct v4l2_frmival_stepwise {
                     struct v4l2_fract min;
                     struct v4l2_fract max;
                     struct v4l2_fract step;
             };

     VIDIOC_S_PARM struct v4l2_streamparm *
             Set streaming parameters.

             struct v4l2_streamparm {
                     enum v4l2_buf_type      type;
                     union {
                             struct v4l2_captureparm capture;
                             struct v4l2_outputparm  output;
                             u_int8_t                raw_data[200];
                     } parm;
             };

             struct v4l2_captureparm {
                     u_int32_t       capability;
                     u_int32_t       capturemode;
                     struct v4l2_fract       timeperframe;
                     u_int32_t       extendedmode;
                     u_int32_t       readbuffers;
                     u_int32_t       reserved[4];
             };

             struct v4l2_outputparm  {
                     u_int32_t       capability;
                     u_int32_t       outputmode;
                     struct v4l2_fract       timeperframe;
                     u_int32_t       extendedmode;
                     u_int32_t       writebuffers;
                     u_int32_t       reserved[4];
             };

     VIDIOC_G_PARM struct v4l2_streamparm *
             Get the streaming parameters.

             Same structures as for VIDIOC_S_PARM.

     VIDIOC_QUERYCTRL struct v4l2_queryctrl *
             Enumerate control items.

             struct v4l2_queryctrl {
                     u_int32_t               id;
                     enum v4l2_ctrl_type     type;
                     u_int8_t                name[32];
                     int32_t                 minimum;
                     int32_t                 maximum;
                     int32_t                 step;
                     int32_t                 default_value;
                     u_int32_t               flags;
                     u_int32_t               reserved[2];
             };

     Command independent enumerations are:

     enum v4l2_buf_type {
             V4L2_BUF_TYPE_VIDEO_CAPTURE = 1,
             V4L2_BUF_TYPE_VIDEO_OUTPUT = 2,
             V4L2_BUF_TYPE_VIDEO_OVERLAY = 3,
             V4L2_BUF_TYPE_VBI_CAPTURE = 4,
             V4L2_BUF_TYPE_VBI_OUTPUT = 5,
             V4L2_BUF_TYPE_SLICED_VBI_CAPTURE = 6,
             V4L2_BUF_TYPE_SLICED_VBI_OUTPUT = 7,
             V4L2_BUF_TYPE_VIDEO_OUTPUT_OVERLAY = 8,
             V4L2_BUF_TYPE_PRIVATE = 0x80,
     };

     enum v4l2_memory {
             V4L2_MEMORY_MMAP = 1,
             V4L2_MEMORY_USERPTR = 2,
             V4L2_MEMORY_OVERLAY = 3,
     };

     enum v4l2_ctrl_type {
             V4L2_CTRL_TYPE_INTEGER = 1,
             V4L2_CTRL_TYPE_BOOLEAN = 2,
             V4L2_CTRL_TYPE_MENU = 3,
             V4L2_CTRL_TYPE_BUTTON = 4,
             V4L2_CTRL_TYPE_INTEGER64 = 5,
             V4L2_CTRL_TYPE_CTRL_CLASS = 6,
     };

     enum v4l2_frmivaltypes {
             V4L2_FRMIVAL_TYPE_DISCRETE = 1,
             V4L2_FRMIVAL_TYPE_CONTINUOUS = 2,
             V4L2_FRMIVAL_TYPE_STEPWISE = 3,
     };

     Command independent structures are:

     struct v4l2_pix_format {
             u_int32_t               width;
             u_int32_t               height;
             u_int32_t               pixelformat;
             enum v4l2_field         field;
             u_int32_t               bytesperline;
             u_int32_t               sizeimage;
             enum v4l2_colorspace    colorspace;
             u_int32_t               priv;
     };

     struct v4l2_window {
             struct v4l2_rect         w;
             enum v4l2_field          chromakey;
             struct v4l2_clip         __user *clips;
             u_int32_t                clipcount;
             void __user             *bitmap;
             u_int8_t                 global_alpha;
     };

     struct v4l2_vbi_format {
             u_int32_t               sampling_rate;
             u_int32_t               offset;
             u_int32_t               samples_per_line;
             u_int32_t               sample_format;
             int32_t                 start[2];
             u_int32_t               count[2];
             u_int32_t               flags;
             u_int32_t               reserved[2];
     };

     struct v4l2_sliced_vbi_format {
             u_int16_t       service_set;
             u_int16_t       service_lines[2][24];
             u_int32_t       io_size;
             u_int32_t       reserved[2];
     };

     struct v4l2_fract {
             u_int32_t       numerator;
             u_int32_t       denominator;
     };

     Command independent typedefs are:

     typedef u_int64_t       v4l2_std_id;

READ
     Video data can be accessed via the read(2) system call.  The main itera-
     tion for userland applications occurs as follow:

           1.   Open /dev/video* via the open(2) system call.
           2.   Read video data from the device via the read(2) system call.
                The video stream will be started automatically with the first
                read, which means there is no need to issue a VIDIOC_STREAMON
                command.  The read will always return a consistent video
                frame, if no error occurs.
           3.   Process video data and start over again with step 2.
           4.   When finished stop the video stream via the close(2) system
                call.

     The select(2) and poll(2) system calls are supported for this access
     type.  They will signal when a frame is ready for reading without block-
     ing.

MMAP
     Video data can be accessed via the mmap(2) system call.  The main itera-
     tion for userland applications occurs as follow:

           1.   Open /dev/video* via the open(2) system call.
           2.   Request desired number of buffers via the VIDIOC_REQBUFS ioctl
                command.  The maximum number of available buffers is normally
                limited by the hardware driver.
           3.   Get the length and offset for the previously requested buffers
                via the VIDIOC_QUERYBUF ioctl command and map the buffers via
                the mmap(2) system call.
           4.   Initially queue the buffers via the VIDIOC_QBUF ioctl command.
           5.   Start the video stream via the VIDIOC_STREAMON ioctl command.
           6.   Dequeue one buffer via the VIDIOC_DQBUF ioctl command.  If the
                queue is empty the ioctl will block until a buffer gets queued
                or an error occurs (e.g. a timeout).
           7.   Requeue the buffer via the VIDIOC_QBUF ioctl command.
           8.   Process video data and start over again with step 6.
           9.   When finished stop the video stream via the VIDIOC_STREAMOFF
                ioctl command.

     The select(2) and poll(2) system calls are supported for this access
     type.  They will signal when at least one frame is ready for dequeuing,
     allowing to call the VIDIOC_DQBUF ioctl command without blocking.

FILES
     /dev/video

SEE ALSO
     ioctl(2), uvideo(4)

HISTORY
     The video driver first appeared in OpenBSD 4.4.

BSD                             March 24, 2017                             BSD