.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later .. c:namespace:: V4L .. _VIDIOC_OVERLAY: ******************** ioctl VIDIOC_OVERLAY ******************** Name ==== VIDIOC_OVERLAY - Start or stop video overlay Synopsis ======== .. c:macro:: VIDIOC_OVERLAY ``int ioctl(int fd, VIDIOC_OVERLAY, const int *argp)`` Arguments ========= ``fd`` File descriptor returned by :c:func:`open()`. ``argp`` Pointer to an integer. Description =========== This ioctl is part of the :ref:`video overlay ` I/O method. Applications call :ref:`VIDIOC_OVERLAY` to start or stop the overlay. It takes a pointer to an integer which must be set to zero by the application to stop overlay, to one to start. Drivers do not support :ref:`VIDIOC_STREAMON` or :ref:`VIDIOC_STREAMOFF ` with ``V4L2_BUF_TYPE_VIDEO_OVERLAY``. 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 ` chapter. EINVAL The overlay parameters have not been set up. See :ref:`overlay` for the necessary steps.