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VIDEO(4)	       FreeBSD Kernel Interfaces Manual		      VIDEO(4)

NAME
     video -- device-independent video driver layer

SYNOPSIS
     video* at uvideo?

     #include <sys/types.h>
     #include <sys/ioctl.h>
     #include <sys/videoio.h>

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.

     For security reasons video	recording is blanked by	default.  To achieve
     this, the video driver blanks image data received from the	underlying
     video hardware driver.  The superuser can change this behavior using the
     kern.video.record sysctl(2) variable:

	   kern.video.record=0	   # Recording is blanked (default)
	   kern.video.record=1	   # Recording is enabled

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	     device_caps;
		     u_int32_t	     reserved[3];
	     };

     VIDIOC_ENUM_FMT struct v4l2_fmtdesc *
	     Enumerate image formats.

	     struct v4l2_fmtdesc {
		     u_int32_t	     index;
		     u_int32_t	     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	{
		     u_int32_t	     type;
		     union {
			     struct v4l2_pix_format	     pix;
			     struct v4l2_pix_format_mplane   pix_mp;
			     struct v4l2_window		     win;
			     struct v4l2_vbi_format	     vbi;
			     struct v4l2_sliced_vbi_format   sliced;
			     struct v4l2_sdr_format	     sdr;
			     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	     capabilities;
		     u_int32_t	     reserved[3];
	     };

     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;
		     u_int32_t	     type;
		     u_int32_t	     memory;
		     u_int32_t	     reserved[2];
	     };

     VIDIOC_QUERYBUF struct v4l2_buffer	*
	     Query the status of a buffer.

	     struct v4l2_buffer	{
		     u_int32_t		     index;
		     u_int32_t		     type;
		     u_int32_t		     bytesused;
		     u_int32_t		     flags;
		     u_int32_t		     field;
		     struct timeval	     timestamp;
		     struct v4l2_timecode    timecode;
		     u_int32_t		     sequence;
		     u_int32_t		     memory;
		     union {
			     u_int32_t		     offset;
			     unsigned long	     userptr;
			     struct v4l2_plane	     *planes;
			     int32_t		     fd;
		     } m;
		     u_int32_t		     length;
		     u_int32_t		     reserved2;
		     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_frmivalenum {
		     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;
		     };
		     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 {
		     u_int32_t	     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;
		     u_int32_t	     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_VIDEO_CAPTURE_MPLANE	= 9,
	     V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE = 10,
	     V4L2_BUF_TYPE_SDR_CAPTURE = 11,
	     V4L2_BUF_TYPE_SDR_OUTPUT =	12,
	     V4L2_BUF_TYPE_PRIVATE = 0x80,
     };

     enum v4l2_memory {
	     V4L2_MEMORY_MMAP =	1,
	     V4L2_MEMORY_USERPTR = 2,
	     V4L2_MEMORY_OVERLAY = 3,
	     V4L2_MEMORY_DMABUF	= 4,
     };

     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,
	     V4L2_CTRL_TYPE_STRING = 7,
	     V4L2_CTRL_TYPE_BITMASK = 8,
	     V4L2_CTRL_TYPE_INTEGER_MENU = 9,
	     V4L2_CTRL_COMPOUND_TYPES =	0x0100,
	     V4L2_CTRL_TYPE_U8 = 0x0100,
	     V4L2_CTRL_TYPE_U16	= 0x0101,
	     V4L2_CTRL_TYPE_U32	= 0x0102,
     };

     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;
	     u_int32_t	     field;
	     u_int32_t	     bytesperline;
	     u_int32_t	     sizeimage;
	     u_int32_t	     colorspace;
	     u_int32_t	     priv;
	     u_int32_t	     flags;
	     u_int32_t	     ycbcr_enc;
	     union {
		     u_int32_t	     ycbcr_enc;
		     u_int32_t	     hsv_enc;
	     };
	     u_int32_t	     quantization;
	     u_int32_t	     xfer_func;
     };

     struct v4l2_window	{
	     struct v4l2_rect	     w;
	     u_int32_t		     field;
	     u_int32_t		     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), poll(2) and	kqueue(2) system calls are supported for this
     access type.  They	will signal when a frame is ready for reading without
     blocking.

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.	Process	video data.
	   8.	Requeue	the buffer via the VIDIOC_QBUF ioctl command and start
		over again with	step 6.
	   9.	When finished stop the video stream via	the VIDIOC_STREAMOFF
		ioctl command.

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

FILES
     /dev/video

SEE ALSO
     video(1), ioctl(2), uvideo(4)

HISTORY
     The video driver first appeared in	OpenBSD	4.4.

FreeBSD	13.0		       December	29, 2020		  FreeBSD 13.0

NAME | SYNOPSIS | DESCRIPTION | IOCTLS | READ | MMAP | FILES | SEE ALSO | HISTORY

Want to link to this manual page? Use this URL:
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