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Fixing Linux Webcams


  v4l2-ctl --list-devices
  v4l2-ctl -d /dev/video0 --list-ctrls
  v4l2-ctl --get-ctrl=white_balance_temperature
  v4l2-ctl --set-ctrl=white_balance_temperature=4000
  v4l2-ctl --set-ctrl=white_balance_temperature=4000 -d /dev/video0
  v4l2-ctl --set-ctrl=white_balance_temperature_auto=1
  v4l2-ctl --set-ctrl=white_balance_temperature_auto=0
  v4l2-ctl --set-ctrl=white_balance_temperature_auto=4000
  v4l2-ctl --set-ctrl=exposure_auto=3
  v4l2-ctl --set-ctrl=exposure_auto_priority=0
  v4l2-ctl --set-ctrl=exposure_absolute=250
  v4l2-ctl --set-ctrl=exposure_absolute=0
  v4l2-ctl --set-ctrl=exposure_absolute=250
  v4l2-ctl --set-ctrl=gain=0
  v4l2-ctl -d /dev/video0 --list-ctrls
  v4l2-ctl --set-ctrl=white_balance_temperature_auto=4000
  v4l2-ctl --set-ctrl=white_balance_temperature_auto=0
  v4l2-ctl --set-ctrl=white_balance_temperature=4000
 v4l2-ctl -d /dev/video0 --list-ctrls



This article is great:   https://www.kurokesu.com/main/2016/01/16/manual-usb-camera-settings-in-linux/


v4l2-ctl -d /dev/video0 --list-ctrls
                     brightness 0x00980900 (int)    : min=0 max=255 step=1 default=128 value=128
                       contrast 0x00980901 (int)    : min=0 max=255 step=1 default=128 value=128
                     saturation 0x00980902 (int)    : min=0 max=255 step=1 default=128 value=128
 white_balance_temperature_auto 0x0098090c (bool)   : default=1 value=0
                           gain 0x00980913 (int)    : min=0 max=255 step=1 default=0 value=0
           power_line_frequency 0x00980918 (menu)   : min=0 max=2 default=2 value=2
      white_balance_temperature 0x0098091a (int)    : min=2000 max=6500 step=1 default=4000 value=4000
                      sharpness 0x0098091b (int)    : min=0 max=255 step=1 default=128 value=128
         backlight_compensation 0x0098091c (int)    : min=0 max=1 step=1 default=0 value=0
                  exposure_auto 0x009a0901 (menu)   : min=0 max=3 default=3 value=3
              exposure_absolute 0x009a0902 (int)    : min=3 max=2047 step=1 default=250 value=83 flags=inactive
         exposure_auto_priority 0x009a0903 (bool)   : default=0 value=0
                   pan_absolute 0x009a0908 (int)    : min=-36000 max=36000 step=3600 default=0 value=0
                  tilt_absolute 0x009a0909 (int)    : min=-36000 max=36000 step=3600 default=0 value=0
                 focus_absolute 0x009a090a (int)    : min=0 max=250 step=5 default=0 value=0 flags=inactive
                     focus_auto 0x009a090c (bool)   : default=1 value=1
                  zoom_absolute 0x009a090d (int)    : min=100 max=500 step=1 default=100 value=100




v4l2-ctl --list-devices
HD Pro Webcam C920 (usb-70090000.xusb-2.2):
/dev/video0


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