linux/Documentation/media/uapi/v4l/vidioc-g-dv-timings.rst

.. -*- coding: utf-8; mode: rst -*-

.. _VIDIOC_G_DV_TIMINGS:

**********************************************
ioctl VIDIOC_G_DV_TIMINGS, VIDIOC_S_DV_TIMINGS
**********************************************

Name
====

VIDIOC_G_DV_TIMINGS - VIDIOC_S_DV_TIMINGS - VIDIOC_SUBDEV_G_DV_TIMINGS - VIDIOC_SUBDEV_S_DV_TIMINGS - Get or set DV timings for input or output


Synopsis
========

.. cpp:function:: int ioctl( int fd, int request, struct v4l2_dv_timings *argp )


Arguments
=========

``fd``
    File descriptor returned by :ref:`open() <func-open>`.

``request``
    VIDIOC_G_DV_TIMINGS, VIDIOC_S_DV_TIMINGS,
    VIDIOC_SUBDEV_G_DV_TIMINGS, VIDIOC_SUBDEV_S_DV_TIMINGS

``argp``


Description
===========

To set DV timings for the input or output, applications use the
:ref:`VIDIOC_S_DV_TIMINGS <VIDIOC_G_DV_TIMINGS>` ioctl and to get the current timings,
applications use the :ref:`VIDIOC_G_DV_TIMINGS <VIDIOC_G_DV_TIMINGS>` ioctl. The detailed timing
information is filled in using the structure struct
:ref:`v4l2_dv_timings <v4l2-dv-timings>`. These ioctls take a
pointer to the struct :ref:`v4l2_dv_timings <v4l2-dv-timings>`
structure as argument. If the ioctl is not supported or the timing
values are not correct, the driver returns ``EINVAL`` error code.

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


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
:ref:`Generic Error Codes <gen-errors>` chapter.

EINVAL
    This ioctl is not supported, or the :ref:`VIDIOC_S_DV_TIMINGS <VIDIOC_G_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.


.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|

.. _v4l2-bt-timings:

.. flat-table:: struct v4l2_bt_timings
    :header-rows:  0
    :stub-columns: 0
    :widths:       1 1 2


    -  .. row 1

       -  __u32

       -  ``width``

       -  Width of the active video in pixels.

    -  .. row 2

       -  __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.

    -  .. row 3

       -  __u32

       -  ``interlaced``

       -  Progressive (``V4L2_DV_PROGRESSIVE``) or interlaced (``V4L2_DV_INTERLACED``).

    -  .. row 4

       -  __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.

    -  .. row 5

       -  __u64

       -  ``pixelclock``

       -  Pixel clock in Hz. Ex. 74.25MHz->74250000

    -  .. row 6

       -  __u32

       -  ``hfrontporch``

       -  Horizontal front porch in pixels

    -  .. row 7

       -  __u32

       -  ``hsync``

       -  Horizontal sync length in pixels

    -  .. row 8

       -  __u32

       -  ``hbackporch``

       -  Horizontal back porch in pixels

    -  .. row 9

       -  __u32

       -  ``vfrontporch``

       -  Vertical front porch in lines. For interlaced formats this refers
	  to the odd field (aka field 1).

    -  .. row 10

       -  __u32

       -  ``vsync``

       -  Vertical sync length in lines. For interlaced formats this refers
	  to the odd field (aka field 1).

    -  .. row 11

       -  __u32

       -  ``vbackporch``

       -  Vertical back porch in lines. For interlaced formats this refers
	  to the odd field (aka field 1).

    -  .. row 12

       -  __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.

    -  .. row 13

       -  __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.

    -  .. row 14

       -  __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.

    -  .. row 15

       -  __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
	  :ref:`dv-bt-standards` for a list of standards.

    -  .. row 16

       -  __u32

       -  ``flags``

       -  Several flags giving more information about the format. See
	  :ref:`dv-bt-flags` for a description of the flags.



.. tabularcolumns:: |p{3.5cm}|p{3.5cm}|p{7.0cm}|p{3.5cm}|

.. _v4l2-dv-timings:

.. flat-table:: struct v4l2_dv_timings
    :header-rows:  0
    :stub-columns: 0
    :widths:       1 1 2 1


    -  .. row 1

       -  __u32

       -  ``type``

       -
       -  Type of DV timings as listed in :ref:`dv-timing-types`.

    -  .. row 2

       -  union

       -
       -

    -  .. row 3

       -
       -  struct :ref:`v4l2_bt_timings <v4l2-bt-timings>`

       -  ``bt``

       -  Timings defined by BT.656/1120 specifications

    -  .. row 4

       -
       -  __u32

       -  ``reserved``\ [32]

       -

.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|

.. _dv-timing-types:

.. flat-table:: DV Timing types
    :header-rows:  0
    :stub-columns: 0
    :widths:       1 1 2


    -  .. row 1

       -  Timing type

       -  value

       -  Description

    -  .. row 2

       -
       -
       -

    -  .. row 3

       -  ``V4L2_DV_BT_656_1120``

       -  0

       -  BT.656/1120 timings



.. _dv-bt-standards:

.. flat-table:: DV BT Timing standards
    :header-rows:  0
    :stub-columns: 0


    -  .. row 1

       -  Timing standard

       -  Description

    -  .. row 3

       -  ``V4L2_DV_BT_STD_CEA861``

       -  The timings follow the CEA-861 Digital TV Profile standard

    -  .. row 4

       -  ``V4L2_DV_BT_STD_DMT``

       -  The timings follow the VESA Discrete Monitor Timings standard

    -  .. row 5

       -  ``V4L2_DV_BT_STD_CVT``

       -  The timings follow the VESA Coordinated Video Timings standard

    -  .. row 6

       -  ``V4L2_DV_BT_STD_GTF``

       -  The timings follow the VESA Generalized Timings Formula standard


.. tabularcolumns:: |p{6.0cm}|p{11.5cm}|

.. _dv-bt-flags:

.. flat-table:: DV BT Timing flags
    :header-rows:  0
    :stub-columns: 0


    -  .. row 1

       -  Flag

       -  Description

    -  .. row 3

       -  ``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.

    -  .. row 4

       -  ``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.

    -  .. row 5

       -  ``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.

    -  .. row 6

       -  ``V4L2_DV_FL_HALF_LINE``

       -  Specific to interlaced formats: if set, then the vertical
	  frontporch of field 1 (aka the odd field) is really one half-line
	  longer and the vertical backporch of 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.

    -  .. row 7

       -  ``V4L2_DV_FL_IS_CE_VIDEO``

       -  If set, then this is a Consumer Electronics (CE) video format.
	  Such formats differ from other formats (commonly called IT
	  formats) in that if R'G'B' encoding is used then by default the
	  R'G'B' values use limited range (i.e. 16-235) as opposed to full
	  range (i.e. 0-255). All formats defined in CEA-861 except for the
	  640x480p59.94 format are CE formats.