VIDEO(4) | Device Drivers Manual | VIDEO(4) |
video
—
device-independent video driver layer
video* at uvideo?
#include <sys/types.h>
#include <sys/ioctl.h>
#include <sys/videoio.h>
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.
The following ioctl(2) commands are supported:
VIDIOC_QUERYCAP
struct v4l2_capability *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 *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 *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 *Same structure as for
VIDIOC_S_FMT
.
VIDIOC_ENUMINPUT
struct v4l2_input *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 *VIDIOC_S_INPUT
int *VIDIOC_REQBUFS
struct v4l2_requestbuffers *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 *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 *Same structure as for
VIDIOC_QUERYBUF
.
VIDIOC_DQBUF
struct v4l2_buffer *Same structure as for
VIDIOC_QUERYBUF
.
VIDIOC_STREAMON
int *VIDIOC_STREAMOFF
int *VIDIOC_TRY_FMT
struct v4l2_format *Same structure as for
VIDIOC_S_FMT
.
VIDIOC_ENUM_FRAMEINTERVALS
struct v4l2_frmivalenum *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 *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 *Same structures as for
VIDIOC_S_PARM
.
VIDIOC_QUERYCTRL
struct v4l2_queryctrl *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;
Video data can be accessed via the read(2) system call. The main iteration for userland applications occurs as follow:
VIDIOC_STREAMON
command. The read will always return a consistent video frame, if no error
occurs.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 blocking.
Video data can be accessed via the mmap(2) system call. The main iteration for userland applications occurs as follow:
VIDIOC_REQBUFS
ioctl command. The maximum number
of available buffers is normally limited by the hardware driver.VIDIOC_QUERYBUF
ioctl command and map the buffers
via the mmap(2) system
call.VIDIOC_QBUF
ioctl command.VIDIOC_STREAMON
ioctl command.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).VIDIOC_QBUF
ioctl
command and start over again with step 6.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.
The video
driver first appeared in
OpenBSD 4.4.
February 2, 2017 | OpenBSD-6.2 |