vidioc-g-std.rst 2.0 KB
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.. -*- coding: utf-8; mode: rst -*-

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.. _VIDIOC_G_STD:
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********************************
ioctl VIDIOC_G_STD, VIDIOC_S_STD
********************************

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Name
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====
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VIDIOC_G_STD - VIDIOC_S_STD - Query or select the video standard of the current input
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Synopsis
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========

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.. c:function:: int ioctl( int fd, VIDIOC_G_STD, v4l2_std_id *argp )
    :name: VIDIOC_G_STD
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.. c:function:: int ioctl( int fd, VIDIOC_S_STD, const v4l2_std_id *argp )
    :name: VIDIOC_S_STD
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Arguments
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=========

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

``argp``


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

To query and select the current video standard applications use the
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:ref:`VIDIOC_G_STD <VIDIOC_G_STD>` and :ref:`VIDIOC_S_STD <VIDIOC_G_STD>` ioctls which take a pointer to a
:ref:`v4l2_std_id <v4l2-std-id>` type as argument. :ref:`VIDIOC_G_STD <VIDIOC_G_STD>`
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can return a single flag or a set of flags as in struct
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:c:type:`v4l2_standard` field ``id``. The flags must be
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unambiguous such that they appear in only one enumerated
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:c:type:`struct v4l2_standard <v4l2_standard>` structure.
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:ref:`VIDIOC_S_STD <VIDIOC_G_STD>` accepts one or more flags, being a write-only ioctl it
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does not return the actual new standard as :ref:`VIDIOC_G_STD <VIDIOC_G_STD>` does. When
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no flags are given or the current input does not support the requested
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standard the driver returns an ``EINVAL`` error code. When the standard set
is ambiguous drivers may return ``EINVAL`` or choose any of the requested
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standards. If the current input or output does not support standard
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video timings (e.g. if :ref:`VIDIOC_ENUMINPUT`
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does not set the ``V4L2_IN_CAP_STD`` flag), then ``ENODATA`` error code is
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returned.


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Return Value
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============

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
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    The :ref:`VIDIOC_S_STD <VIDIOC_G_STD>` parameter was unsuitable.
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ENODATA
    Standard video timings are not supported for this input or output.
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