VIDIOC_G_SLICED_VBI_CAP — Query sliced VBI capabilities


int ioctl(int  fd,
 int  request,
 struct v4l2_sliced_vbi_cap * argp);



File descriptor returned by open().





To find out which data services are supported by a sliced VBI capture or output device, applications initialize the type field of a struct 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 error code 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.

Table 96. struct v4l2_sliced_vbi_cap

__u16service_setA set of all data services supported by the driver. Equal to the union of all elements of the service_lines array.
__u16service_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 Table 97, “Sliced VBI services”. Array indices map to ITU-R line numbers (see also Figure 4.2, “ITU-R 525 line numbering (M/NTSC and M/PAL)” and Figure 4.3, “ITU-R 625 line numbering”) as follows:
  Element525 line systems625 line systems
  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 Section 4.8, “Sliced VBI Data Interface”.
  Drivers must set service_lines[0][0] and service_lines[1][0] to zero.
enum v4l2_buf_typetypeType of the data stream, see Table 3.2, “enum v4l2_buf_type”. Should be V4L2_BUF_TYPE_SLICED_VBI_CAPTURE or V4L2_BUF_TYPE_SLICED_VBI_OUTPUT.  
__u32reserved[3]This array is reserved for future extensions. Applications and drivers must set it to zero.

Table 97. Sliced VBI services

SymbolValueReferenceLines, usuallyPayload
V4L2_SLICED_TELETEXT_B (Teletext System B)0x0001[ETS 300 706], [ITU BT.653]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_VPS0x0400[ETS 300 231]PAL line 16Byte number 3 to 15 according to Figure 9 of ETS 300 231, lsb first transmitted.
V4L2_SLICED_CAPTION_5250x1000[EIA 608-B]NTSC line 21, 284 (second field 21)Two bytes in transmission order, including parity bit, lsb first transmitted.
V4L2_SLICED_WSS_6250x4000[EN 300 294], [ITU BT.1119]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_5250x1000Set of services applicable to 525 line systems.
V4L2_SLICED_VBI_6250x4401Set of services applicable to 625 line systems.

Return Value

On success 0 is returned, on error -1 and the errno variable is set appropriately:


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