ioctl VIDIOC_G_DV_TIMINGS, VIDIOC_S_DV_TIMINGS

&manvol;

VIDIOC_G_DV_TIMINGS

VIDIOC_S_DV_TIMINGS

Get or set DV timings for input or output

    	int ioctl
    	int fd
    	int request
    	struct v4l2_dv_timings *argp

## Arguments

`fd`

- &fd;

`request`

- VIDIOC_G_DV_TIMINGS, VIDIOC_S_DV_TIMINGS

`argp`

## Description

To set DV timings for the input or output, applications use the `VIDIOC_S_DV_TIMINGS` ioctl and to get the current timings, applications use the `VIDIOC_G_DV_TIMINGS` ioctl. The detailed timing information is filled in using the structure &v4l2-dv-timings;. These ioctls take a pointer to the &v4l2-dv-timings; structure as argument. If the ioctl is not supported or the timing values are not correct, the driver returns &EINVAL;.

The `linux/v4l2-dv-timings.h` header can be used to get the timings of the formats in the cea861 and vesadmt standards. If the current input or output does not support DV timings (e.g. if &VIDIOC-ENUMINPUT; does not set the `V4L2_IN_CAP_DV_TIMINGS` flag), then &ENODATA; is returned.

&return-value;

EINVAL

- This ioctl is not supported, or the `VIDIOC_S_DV_TIMINGS` parameter was unsuitable.

ENODATA

- Digital video timings are not supported for this input or output.

EBUSY

- The device is busy and therefore can not change the timings.

## struct v4l2_bt_timings

&cs-str;
__u32 | width | Width of the active video in pixels.
__u32 | height | Height of the active video frame in lines. So for interlaced formats the height of the active video in each field is height/2.
__u32 | interlaced | Progressive (0) or interlaced (1)
__u32 | polarities | This is a bit mask that defines polarities of sync signals. bit 0 (V4L2_DV_VSYNC_POS_POL) is for vertical sync polarity and bit 1 (V4L2_DV_HSYNC_POS_POL) is for horizontal sync polarity. If the bit is set (1) it is positive polarity and if is cleared (0), it is negative polarity.
__u64 | pixelclock | Pixel clock in Hz. Ex. 74.25MHz->74250000
__u32 | hfrontporch | Horizontal front porch in pixels
__u32 | hsync | Horizontal sync length in pixels
__u32 | hbackporch | Horizontal back porch in pixels
__u32 | vfrontporch | Vertical front porch in lines. For interlaced formats this refers to the odd field (aka field 1).
__u32 | vsync | Vertical sync length in lines. For interlaced formats this refers to the odd field (aka field 1).
__u32 | vbackporch | Vertical back porch in lines. For interlaced formats this refers to the odd field (aka field 1).
__u32 | il_vfrontporch | Vertical front porch in lines for the even field (aka field 2) of interlaced field formats. Must be 0 for progressive formats.
__u32 | il_vsync | Vertical sync length in lines for the even field (aka field 2) of interlaced field formats. Must be 0 for progressive formats.
__u32 | il_vbackporch | Vertical back porch in lines for the even field (aka field 2) of interlaced field formats. Must be 0 for progressive formats.
__u32 | standards | The video standard(s) this format belongs to. This will be filled in by the driver. Applications must set this to 0. See dv-bt-standards for a list of standards.
__u32 | flags | Several flags giving more information about the format. See dv-bt-flags for a description of the flags.

## struct v4l2_dv_timings

&cs-str;
__u32 | type |  | Type of DV timings as listed in dv-timing-types.
union |  |
| &v4l2-bt-timings; | bt | Timings defined by BT.656/1120 specifications
| __u32 | reserved[32] |

## DV Timing types

&cs-str;
Timing type | value | Description
V4L2_DV_BT_656_1120 | 0 | BT.656/1120 timings

## DV BT Timing standards

&cs-str;
Timing standard | Description
V4L2_DV_BT_STD_CEA861 | The timings follow the CEA-861 Digital TV Profile standard
V4L2_DV_BT_STD_DMT | The timings follow the VESA Discrete Monitor Timings standard
V4L2_DV_BT_STD_CVT | The timings follow the VESA Coordinated Video Timings standard
V4L2_DV_BT_STD_GTF | The timings follow the VESA Generalized Timings Formula standard

## DV BT Timing flags

&cs-str;
Flag | Description
V4L2_DV_FL_REDUCED_BLANKING | CVT/GTF specific: the timings use reduced blanking (CVT) or the 'Secondary GTF' curve (GTF). In both cases the horizontal and/or vertical blanking intervals are reduced, allowing a higher resolution over the same bandwidth. This is a read-only flag, applications must not set this.
V4L2_DV_FL_CAN_REDUCE_FPS | CEA-861 specific: set for CEA-861 formats with a framerate that is a multiple of six. These formats can be optionally played at 1 / 1.001 speed to be compatible with 60 Hz based standards such as NTSC and PAL-M that use a framerate of 29.97 frames per second. If the transmitter can't generate such frequencies, then the flag will also be cleared. This is a read-only flag, applications must not set this.
V4L2_DV_FL_REDUCED_FPS | CEA-861 specific: only valid for video transmitters, the flag is cleared by receivers. It is also only valid for formats with the V4L2_DV_FL_CAN_REDUCE_FPS flag set, for other formats the flag will be cleared by the driver. If the application sets this flag, then the pixelclock used to set up the transmitter is divided by 1.001 to make it compatible with NTSC framerates. If the transmitter can't generate such frequencies, then the flag will also be cleared.
V4L2_DV_FL_HALF_LINE | Specific to interlaced formats: if set, then field 1 (aka the odd field) is really one half-line longer and field 2 (aka the even field) is really one half-line shorter, so each field has exactly the same number of half-lines. Whether half-lines can be detected or used depends on the hardware.