.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
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.. c:namespace:: V4L
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.. _VIDIOC_OVERLAY:
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********************
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ioctl VIDIOC_OVERLAY
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********************
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Name
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====
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VIDIOC_OVERLAY - Start or stop video overlay
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Synopsis
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========
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.. c:macro:: VIDIOC_OVERLAY
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``int ioctl(int fd, VIDIOC_OVERLAY, const int *argp)``
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Arguments
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=========
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``fd``
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File descriptor returned by :c:func:`open()`.
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``argp``
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Pointer to an integer.
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Description
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===========
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This ioctl is part of the :ref:`video overlay <overlay>` I/O method.
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Applications call :ref:`VIDIOC_OVERLAY` to start or stop the overlay. It
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takes a pointer to an integer which must be set to zero by the
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application to stop overlay, to one to start.
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Drivers do not support :ref:`VIDIOC_STREAMON` or
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:ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>` with
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``V4L2_BUF_TYPE_VIDEO_OVERLAY``.
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Return Value
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============
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On success 0 is returned, on error -1 and the ``errno`` variable is set
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appropriately. The generic error codes are described at the
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:ref:`Generic Error Codes <gen-errors>` chapter.
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EINVAL
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The overlay parameters have not been set up. See :ref:`overlay`
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for the necessary steps.
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