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- .. -*- coding: utf-8; mode: rst -*-
- .. _VIDIOC_G_OUTPUT:
- **************************************
- ioctl VIDIOC_G_OUTPUT, VIDIOC_S_OUTPUT
- **************************************
- Name
- ====
- VIDIOC_G_OUTPUT - VIDIOC_S_OUTPUT - Query or select the current video output
- Synopsis
- ========
- .. c:function:: int ioctl( int fd, VIDIOC_G_OUTPUT, int *argp )
- :name: VIDIOC_G_OUTPUT
- .. c:function:: int ioctl( int fd, VIDIOC_S_OUTPUT, int *argp )
- :name: VIDIOC_S_OUTPUT
- Arguments
- =========
- ``fd``
- File descriptor returned by :ref:`open() <func-open>`.
- ``argp``
- Description
- ===========
- To query the current video output applications call the
- :ref:`VIDIOC_G_OUTPUT <VIDIOC_G_OUTPUT>` ioctl with a pointer to an integer where the driver
- stores the number of the output, as in the struct
- :c:type:`v4l2_output` ``index`` field. This ioctl will
- fail only when there are no video outputs, returning the ``EINVAL`` error
- code.
- To select a video output applications store the number of the desired
- output in an integer and call the :ref:`VIDIOC_S_OUTPUT <VIDIOC_G_OUTPUT>` ioctl with a
- pointer to this integer. Side effects are possible. For example outputs
- may support different video standards, so the driver may implicitly
- switch the current standard. standard. Because of these possible side
- effects applications must select an output before querying or
- negotiating any other parameters.
- Information about video outputs is available using the
- :ref:`VIDIOC_ENUMOUTPUT` ioctl.
- 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
- The number of the video output is out of bounds, or there are no
- video outputs at all.
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