ioctl VIDIOC_G_SLICED_VBI_CAP

&manvol;

VIDIOC_G_SLICED_VBI_CAP

Query sliced VBI capabilities

    	int ioctl
    	int fd
    	int request
    	struct v4l2_sliced_vbi_cap *argp

## Arguments

`fd`

- &fd;

`request`

- VIDIOC_G_SLICED_VBI_CAP

`argp`

## Description

To find out which data services are supported by a sliced VBI capture or output device, applications initialize the type field of a &v4l2-sliced-vbi-cap;, clear the reserved array and call the `VIDIOC_G_SLICED_VBI_CAP` ioctl. The driver fills in the remaining fields or returns an &EINVAL; if the sliced VBI API is unsupported or type is invalid.

Note the type field was added, and the ioctl changed from read-only to write-read, in Linux 2.6.19.

## struct v4l2_sliced_vbi_cap

__u16 | service_set | A set of all data services supported by the driver. Equal to the union of all elements of the service_lines array.
__u16 | service_lines[2][24] | Each element of this array contains a set of data services the hardware can look for or insert into a particular scan line. Data services are defined in vbi-services. Array indices map to ITU-R line numbers (see also vbi-525 and vbi-625) as follows:
|  | Element | 525 line systems | 625 line systems
|  | service_lines[0][1] | 1 | 1
|  | service_lines[0][23] | 23 | 23
|  | service_lines[1][1] | 264 | 314
|  | service_lines[1][23] | 286 | 336
|  | The number of VBI lines the hardware can capture or output per frame, or the number of services it can identify on a given line may be limited. For example on PAL line 16 the hardware may be able to look for a VPS or Teletext signal, but not both at the same time. Applications can learn about these limits using the &VIDIOC-S-FMT; ioctl as described in sliced.
|  | Drivers must set service_lines[0][0] and service_lines[1][0] to zero.
&v4l2-buf-type; | type | Type of the data stream, see v4l2-buf-type. Should be `V4L2_BUF_TYPE_SLICED_VBI_CAPTURE` or `V4L2_BUF_TYPE_SLICED_VBI_OUTPUT`.
__u32 | reserved[3] | This array is reserved for future extensions. Applications and drivers must set it to zero.

## Sliced VBI services

Symbol | Value | Reference | Lines, usually | Payload
`V4L2_SLICED_TELETEXT_B` (Teletext System B) | 0x0001 | ets300706, itu653 | PAL/SECAM line 7-22, 320-335 (second field 7-22) | Last 42 of the 45 byte Teletext packet, that is without clock run-in and framing code, lsb first transmitted.
`V4L2_SLICED_VPS` | 0x0400 | ets300231 | PAL line 16 | Byte number 3 to 15 according to Figure 9 of ETS 300 231, lsb first transmitted.
`V4L2_SLICED_CAPTION_525` | 0x1000 | eia608 | NTSC line 21, 284 (second field 21) | Two bytes in transmission order, including parity bit, lsb first transmitted.
`V4L2_SLICED_WSS_625` | 0x4000 | en300294, itu1119 | PAL/SECAM line 23 |
    Byte        0                 1
         msb         lsb  msb           lsb
    Bit  7 6 5 4 3 2 1 0  x x 13 12 11 10 9
`V4L2_SLICED_VBI_525` | 0x1000 | Set of services applicable to 525 line systems.
`V4L2_SLICED_VBI_625` | 0x4401 | Set of services applicable to 625 line systems.

&return-value;

EINVAL

- The device does not support sliced VBI capturing or output, or the value in the type field is wrong.