7.20. ioctl VIDIOC_ENUMSTD, VIDIOC_SUBDEV_ENUMSTD

7.20.1. Name

VIDIOC_ENUMSTD - VIDIOC_SUBDEV_ENUMSTD - Enumerate supported video standards

7.20.2. Synopsis

VIDIOC_ENUMSTD

int ioctl(int fd, VIDIOC_ENUMSTD, struct v4l2_standard *argp)

VIDIOC_SUBDEV_ENUMSTD

int ioctl(int fd, VIDIOC_SUBDEV_ENUMSTD, struct v4l2_standard *argp)

7.20.3. Arguments

fd

File descriptor returned by open().

argp

Pointer to struct v4l2_standard.

7.20.4. Description

To query the attributes of a video standard, especially a custom (driver defined) one, applications initialize the index field of struct v4l2_standard and call the ioctl VIDIOC_ENUMSTD, VIDIOC_SUBDEV_ENUMSTD ioctl with a pointer to this structure. Drivers fill the rest of the structure or return an EINVAL error code when the index is out of bounds. To enumerate all standards applications shall begin at index zero, incrementing by one until the driver returns EINVAL. Drivers may enumerate a different set of standards after switching the video input or output. [1]

type v4l2_standard

struct v4l2_standard

__u32	index	Number of the video standard, set by the application.
v4l2_std_id	id	The bits in this field identify the standard as one of the common standards listed in typedef v4l2_std_id, or if bits 32 to 63 are set as custom standards. Multiple bits can be set if the hardware does not distinguish between these standards, however separate indices do not indicate the opposite. The id must be unique. No other enumerated struct v4l2_standard structure, for this input or output anyway, can contain the same set of bits.
__u8	name[24]	Name of the standard, a NUL-terminated ASCII string, for example: "PAL-B/G", "NTSC Japan". This information is intended for the user.
struct v4l2_fract	frameperiod	The frame period (not field period) is numerator / denominator. For example M/NTSC has a frame period of 1001 / 30000 seconds.
__u32	framelines	Total lines per frame including blanking, e. g. 625 for B/PAL.
__u32	reserved[4]	Reserved for future extensions. Drivers must set the array to zero.

type v4l2_fract

struct v4l2_fract

__u32	numerator
__u32	denominator

typedef v4l2_std_id

__u64

v4l2_std_id

This type is a set, each bit representing another video standard as listed below and in Video Standards (based on itu470). The 32 most significant bits are reserved for custom (driver defined) video standards.

#define V4L2_STD_PAL_B          ((v4l2_std_id)0x00000001)
#define V4L2_STD_PAL_B1         ((v4l2_std_id)0x00000002)
#define V4L2_STD_PAL_G          ((v4l2_std_id)0x00000004)
#define V4L2_STD_PAL_H          ((v4l2_std_id)0x00000008)
#define V4L2_STD_PAL_I          ((v4l2_std_id)0x00000010)
#define V4L2_STD_PAL_D          ((v4l2_std_id)0x00000020)
#define V4L2_STD_PAL_D1         ((v4l2_std_id)0x00000040)
#define V4L2_STD_PAL_K          ((v4l2_std_id)0x00000080)

#define V4L2_STD_PAL_M          ((v4l2_std_id)0x00000100)
#define V4L2_STD_PAL_N          ((v4l2_std_id)0x00000200)
#define V4L2_STD_PAL_Nc         ((v4l2_std_id)0x00000400)
#define V4L2_STD_PAL_60         ((v4l2_std_id)0x00000800)

V4L2_STD_PAL_60 is a hybrid standard with 525 lines, 60 Hz refresh rate, and PAL color modulation with a 4.43 MHz color subcarrier. Some PAL video recorders can play back NTSC tapes in this mode for display on a 50/60 Hz agnostic PAL TV.

#define V4L2_STD_NTSC_M         ((v4l2_std_id)0x00001000)
#define V4L2_STD_NTSC_M_JP      ((v4l2_std_id)0x00002000)
#define V4L2_STD_NTSC_443       ((v4l2_std_id)0x00004000)

V4L2_STD_NTSC_443 is a hybrid standard with 525 lines, 60 Hz refresh rate, and NTSC color modulation with a 4.43 MHz color subcarrier.

#define V4L2_STD_NTSC_M_KR      ((v4l2_std_id)0x00008000)

#define V4L2_STD_SECAM_B        ((v4l2_std_id)0x00010000)
#define V4L2_STD_SECAM_D        ((v4l2_std_id)0x00020000)
#define V4L2_STD_SECAM_G        ((v4l2_std_id)0x00040000)
#define V4L2_STD_SECAM_H        ((v4l2_std_id)0x00080000)
#define V4L2_STD_SECAM_K        ((v4l2_std_id)0x00100000)
#define V4L2_STD_SECAM_K1       ((v4l2_std_id)0x00200000)
#define V4L2_STD_SECAM_L        ((v4l2_std_id)0x00400000)
#define V4L2_STD_SECAM_LC       ((v4l2_std_id)0x00800000)

/* ATSC/HDTV */
#define V4L2_STD_ATSC_8_VSB     ((v4l2_std_id)0x01000000)
#define V4L2_STD_ATSC_16_VSB    ((v4l2_std_id)0x02000000)

V4L2_STD_ATSC_8_VSB and V4L2_STD_ATSC_16_VSB are U.S. terrestrial digital TV standards. Presently the V4L2 API does not support digital TV. See also the Linux DVB API at https://linuxtv.org.

#define V4L2_STD_PAL_BG         (V4L2_STD_PAL_B         |
                 V4L2_STD_PAL_B1        |
                 V4L2_STD_PAL_G)
#define V4L2_STD_B              (V4L2_STD_PAL_B         |
                 V4L2_STD_PAL_B1        |
                 V4L2_STD_SECAM_B)
#define V4L2_STD_GH             (V4L2_STD_PAL_G         |
                 V4L2_STD_PAL_H         |
                 V4L2_STD_SECAM_G       |
                 V4L2_STD_SECAM_H)
#define V4L2_STD_PAL_DK         (V4L2_STD_PAL_D         |
                 V4L2_STD_PAL_D1        |
                 V4L2_STD_PAL_K)
#define V4L2_STD_PAL            (V4L2_STD_PAL_BG        |
                 V4L2_STD_PAL_DK        |
                 V4L2_STD_PAL_H         |
                 V4L2_STD_PAL_I)
#define V4L2_STD_NTSC           (V4L2_STD_NTSC_M        |
                 V4L2_STD_NTSC_M_JP     |
                 V4L2_STD_NTSC_M_KR)
#define V4L2_STD_MN             (V4L2_STD_PAL_M         |
                 V4L2_STD_PAL_N         |
                 V4L2_STD_PAL_Nc        |
                 V4L2_STD_NTSC)
#define V4L2_STD_SECAM_DK       (V4L2_STD_SECAM_D       |
                 V4L2_STD_SECAM_K       |
                 V4L2_STD_SECAM_K1)
#define V4L2_STD_DK             (V4L2_STD_PAL_DK        |
                 V4L2_STD_SECAM_DK)

#define V4L2_STD_SECAM          (V4L2_STD_SECAM_B       |
                 V4L2_STD_SECAM_G       |
                 V4L2_STD_SECAM_H       |
                 V4L2_STD_SECAM_DK      |
                 V4L2_STD_SECAM_L       |
                 V4L2_STD_SECAM_LC)

#define V4L2_STD_525_60         (V4L2_STD_PAL_M         |
                 V4L2_STD_PAL_60        |
                 V4L2_STD_NTSC          |
                 V4L2_STD_NTSC_443)
#define V4L2_STD_625_50         (V4L2_STD_PAL           |
                 V4L2_STD_PAL_N         |
                 V4L2_STD_PAL_Nc        |
                 V4L2_STD_SECAM)

#define V4L2_STD_UNKNOWN        0
#define V4L2_STD_ALL            (V4L2_STD_525_60        |
                 V4L2_STD_625_50)

Video Standards (based on ITU BT.470)

Characteristics	M/NTSC [2]	M/PAL	N/PAL [3]	B, B1, G/PAL	D, D1, K/PAL	H/PAL	I/PAL	B, G/SECAM	D, K/SECAM	K1/SECAM	L/SECAM
Frame lines	525		625
Frame period (s)	1001/30000		1/25
Chrominance sub-carrier frequency (Hz)	3579545 ± 10	3579611.49 ± 10	4433618.75 ± 5 (3582056.25 ± 5)	4433618.75 ± 5				4433618.75 ± 1	fOR = 4406250 ± 2000, fOB = 4250000 ± 2000
Nominal radio-frequency channel bandwidth (MHz)	6	6	6	B: 7; B1, G: 8	8	8	8	8	8	8	8
Sound carrier relative to vision carrier (MHz)	4.5	4.5	4.5	5.5 ± 0.001 [4] [5] [6] [7]	6.5 ± 0.001	5.5	5.9996 ± 0.0005	5.5 ± 0.001	6.5 ± 0.001	6.5	6.5 [8]

7.20.5. 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 struct v4l2_standard index is out of bounds.

ENODATA

Standard video timings are not supported for this input or output.

[1]

The supported standards may overlap and we need an unambiguous set to find the current standard returned by VIDIOC_G_STD.

[2]

Japan uses a standard similar to M/NTSC (V4L2_STD_NTSC_M_JP).

[3]

The values in brackets apply to the combination N/PAL a.k.a. N_C used in Argentina (V4L2_STD_PAL_Nc).

[4]

In the Federal Republic of Germany, Austria, Italy, the Netherlands, Slovakia and Switzerland a system of two sound carriers is used, the frequency of the second carrier being 242.1875 kHz above the frequency of the first sound carrier. For stereophonic sound transmissions a similar system is used in Australia.

[5]

New Zealand uses a sound carrier displaced 5.4996 ± 0.0005 MHz from the vision carrier.

[6]

In Denmark, Finland, New Zealand, Sweden and Spain a system of two sound carriers is used. In Iceland, Norway and Poland the same system is being introduced. The second carrier is 5.85 MHz above the vision carrier and is DQPSK modulated with 728 kbit/s sound and data multiplex. (NICAM system)

[7]

In the United Kingdom, a system of two sound carriers is used. The second sound carrier is 6.552 MHz above the vision carrier and is DQPSK modulated with a 728 kbit/s sound and data multiplex able to carry two sound channels. (NICAM system)

[8]

In France, a digital carrier 5.85 MHz away from the vision carrier may be used in addition to the main sound carrier. It is modulated in differentially encoded QPSK with a 728 kbit/s sound and data multiplexer capable of carrying two sound channels. (NICAM system)