.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later .. c:namespace:: V4L .. _capture: *********************** Video Capture Interface *********************** Video capture devices sample an analog video signal and store the digitized images in memory. Today nearly all devices can capture at full 25 or 30 frames/second. With this interface applications can control the capture process and move images from the driver into user space. Conventionally V4L2 video capture 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 for video output devices. Querying Capabilities ===================== Devices supporting the video capture interface set the ``V4L2_CAP_VIDEO_CAPTURE`` or ``V4L2_CAP_VIDEO_CAPTURE_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:`video overlay ` (``V4L2_CAP_VIDEO_OVERLAY``) and the :ref:`raw VBI capture ` (``V4L2_CAP_VBI_CAPTURE``) interface. At least one of the read/write or streaming I/O methods must be supported. Tuners and audio inputs are optional. Supplemental Functions ====================== Video capture devices shall support :ref:`audio input