OpenBSD How to use a webcam
       ------------------------------------------------------------------------
       
       +----------------------------------------------------------------------+
       |                                                                      |
       |   Enabling Video Recording (OpenBSD 6.9)                             |
       |                                                                      |
       +----------------------------------------------------------------------+
       
       For privacy reasons, video recording is disabled by default in OpenBSD.
       The sysctl "kern.video.record" may be used to enable it. While recording
       is disabled, a blank video will be shown.
       
         # sysctl kern.video.record=1
         # echo kern.video.record=1 >> /etc/sysctl.conf
       
       +----------------------------------------------------------------------+
       |                                                                      |
       |   Supported Hardware                                                 |
       |                                                                      |
       +----------------------------------------------------------------------+
       
       Most webcams today implement the USB Video Class (UVC) specification,
       which is supported by the uvideo(4) device driver and attaches to the
       video(4) device. The manpage lists some supported devices, but there is
       a good chance that other devices work as well. For example, webcams in
       Lenovo Thinkpad laptops do usually work.
       
       A supported webcam (or other video device) shows up in dmesg like this:
         
         uvideo0 at uhub0 port 8 configuration 1 interface 0 "Azurewave \
             Integrated Camera" rev 2.01/69.05 addr 10
         video0 at uvideo0
         uvideo1 at uhub0 port 8 configuration 1 interface 2 "Azurewave \
             Integrated Camera" rev 2.01/69.05 addr 10
         video1 at uvideo1
       
       You see that an uvideo device was detected and has been attached to
       video0. This device will be accessible through /dev/video0.
       
       Modern laptops sometimes attach a second video device, which is the
       infrared camera for face recognition. The second camera does not produce
       a usable video stream.
       
       You can find the usable camera with the video(1) command:
       
         $ video -q -f /dev/video0
         video device /dev/video0:
           encodings: yuy2
           frame sizes (width x height, in pixels) and rates (in frames per 
           second):
                 320x180: 30
                 320x240: 30
                 352x288: 30
                 424x240: 30
                 640x360: 30
                 640x480: 30
                 848x480: 20
                 960x540: 15
                 1280x720: 10
           controls: brightness, contrast, saturation, hue, gamma, sharpness, 
           white_balance_temperature
         
         $ video -q -f /dev/video1
         video: /dev/video1 has no usable YUV encodings
       
       The usable camera device shows supported resolutions and frameratei.
       Note that the framerates only apply to the uncompressed YUY2 stream.
       More on that in "Recording a webcam stream"
       
       +----------------------------------------------------------------------+
       |                                                                      |
       |   Using a webcam as user                                             |
       |                                                                      |
       +----------------------------------------------------------------------+
       
       To use the webcam as regular user, you need to change the device
       permissions. Only root is allowed to access video devices by default.
       
       One way of allowing your user to access the video devices is to change
       he permissions from ~/.xsession. You can configure doas(1) to perform
       chmod(1) as superuser without asking for a password for your user.
       
         $ doas chown $USER /dev/video0
       
       +----------------------------------------------------------------------+
       |                                                                      |
       |   Recoding a webcam stream                                           |
       |                                                                      |
       +----------------------------------------------------------------------+
       
       This section uses ffplay and ffmpeg from graphics/ffmpeg. To find out
       what your camera is capable of, run the following command:
       
         $ ffplay -f v4l2 -list_formats all -i /dev/video0
         [...]
         [video4linux2,v4l2 @ 0x921f8420800] Raw : yuyv422 : YUYV : 640x480 \
             320x180 320x240 352x288 424x240 640x360 848x480 960x540 1280x720
         [video4linux2,v4l2 @ 0x921f8420800] Compressed: mjpeg : MJPEG : \
             1280x720 320x180 320x240 352x288 424x240 640x360 640x480 848x480
       
       At the end of the output, you'll find two lines similiar to the two
       above.
       
       The first line shows resolutions supported in the uncompressed YUYV
       format. The frame rates in this format can be very low. The second line
       shows the supported MJPEG compressed video resolutions, which deliver
       much higher framerates (usually 30fps or 60fps).
       
       Now try to play the webcam stream. Choose one of the MJPEG resolutions
       and run:
       
         $ ffplay -f v4l2 -input_format mjpeg -video_size 1280x720 -i /dev/video0
         [...]
         Input #0, video4linux2,v4l2, from '/dev/video0':B sq=    0B f=0/0
           Duration: N/A, start: 1599377893.546533, bitrate: N/A
             Stream #0:0: Video: mjpeg (Baseline), yuvj422p(pc, bt470bg/unknown\
                   /unknown), 1280x720, 30 fps, 30 tbr, 1000k tbn, 1000k tbc
       
       The webcam stream should be displayed. Ffplay also shows the used
       resolution and the framerate (fps) used.
       
       If this works, you can go ahead and record the video with ffmpeg:
          
         $ ffmpeg -f v4l2 -input_format mjpeg -video_size 1280x720 \
             -i /dev/video0 ~/video.mkv
       
       +----------------------------------------------------------------------+
       |                                                                      |
       |   Controlling webcam settings                                        |
       |                                                                      |
       +----------------------------------------------------------------------+
       
       Webcams usually have brightness, contrast and other controls. Video(1)
       allows you to alter these settings.
       
       First find out which supported controls your camera has:
       
         $ video -c
         brightness=128
         contrast=32
         saturation=64
         hue=0
         gamma=120
         sharpness=3
         white_balance_temperature=auto
       
       You can change for example the brightness setting to 200:
       
         $ video brightness=200
         brightness: 128 -> 200
       
       If you would like to reset all settings to their defaults, you can do so
       with:
       
         $ video -d
         $ video -c
         brightness=128
         contrast=32
         saturation=64
         hue=0
         gamma=120
         sharpness=3
         white_balance_temperature=auto
       
       Some settings, like the white_balance_temperature support automatic
       adjustments. You can set them to a fixed value or set them to "auto",
       which lets the camera decide and use whatever value it thinks is best.
       
       +----------------------------------------------------------------------+
       |                                                                      |
       |   Access webcam in firefox                                           |
       |                                                                      |
       +----------------------------------------------------------------------+
       
       Chromium has access to /dev/video and /dev/video0 by default. To allow
       Chromium to access other video devices, you need to add the device paths
       to /etc/chromium/unveil.main and /etc/chromium/unveil.utility_video
       
       +----------------------------------------------------------------------+
       |                                                                      |
       |   Access webcam in chromium                                          |
       |                                                                      |
       +----------------------------------------------------------------------+
       
       Firefox has access to /dev/video and /dev/video0 by default. To allow
       Firefox to access other video devices, you need to add the device paths
       o /etc/firefox/unveil.main.
       
       # Changelog:
       # * 2020-11-15: Created
       # * 2021-01-04: Changed styling