.. Permission is granted to copy, distribute and/or modify this .. document under the terms of the GNU Free Documentation License, .. Version 1.1 or any later version published by the Free Software .. Foundation, with no Invariant Sections, no Front-Cover Texts .. and no Back-Cover Texts. A copy of the license is included at .. Documentation/media/uapi/fdl-appendix.rst. .. .. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections .. _output: ********************** Video Output Interface ********************** Video output devices encode stills or image sequences as analog video signal. With this interface applications can control the encoding process and move images from user space to the driver. Conventionally V4L2 video output devices are accessed through character device special files named ``/dev/video`` and ``/dev/video0`` to ``/dev/video63`` with major number 81 and minor numbers 0 to 63. ``/dev/video`` is typically a symbolic link to the preferred video device. .. note:: The same device file names are used also for video capture devices. Querying Capabilities ===================== Devices supporting the video output interface set the ``V4L2_CAP_VIDEO_OUTPUT`` or ``V4L2_CAP_VIDEO_OUTPUT_MPLANE`` flag in the ``capabilities`` field of struct :c:type:`v4l2_capability` returned by the :ref:`VIDIOC_QUERYCAP` ioctl. As secondary device functions they may also support the :ref:`raw VBI output ` (``V4L2_CAP_VBI_OUTPUT``) interface. At least one of the read/write or streaming I/O methods must be supported. Modulators and audio outputs are optional. Supplemental Functions ====================== Video output devices shall support :ref:`audio output