7.40. ioctl VIDIOC_G_SLICED_VBI_CAP

7.40.1. Name

VIDIOC_G_SLICED_VBI_CAP - Query sliced VBI capabilities

7.40.2. Synopsis

int ioctl(int fd, VIDIOC_G_SLICED_VBI_CAP, struct v4l2_sliced_vbi_cap *argp)

7.40.3. Arguments

fd

File descriptor returned by open().

argp

Pointer to struct v4l2_sliced_vbi_cap.

7.40.4. Description

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.

注釈

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

v4l2_sliced_vbi_cap

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 Sliced VBI services. Array indices map to ITU-R line numbers1 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 VBI Data Interface.
		Drivers must set service_lines [0][0] and service_lines[1][0] to zero.
__u32	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.

1

See also Figure 4.2. ITU-R 525 line numbering (M/NTSC and M/PAL) and Figure 4.3. ITU-R 625 line numbering.

Sliced VBI services

Symbol	Value	Reference	Lines, usually	Payload
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_VPS	0x0400	ETS 300 231	PAL line 16	Byte number 3 to 15 according to Figure 9 of ETS 300 231, lsb first transmitted.
V4L2_SLICED_CAPTION_525	0x1000	CEA 608-E	NTSC line 21, 284 (second field 21)	Two bytes in transmission order, including parity bit, lsb first transmitted.
V4L2_SLICED_WSS_625	0x4000	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_525	0x1000	Set of services applicable to 525 line systems.
V4L2_SLICED_VBI_625	0x4401	Set of services applicable to 625 line systems.

7.40.5. Return Value

On success 0 is returned, on error -1 and the errno variable is set appropriately. The generic error codes are described at the Generic Error Codes chapter.

EINVAL

The value in the type field is wrong.