HON’s Wiki # Video4Linux 2 (V4L2)

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• Setup
• Usage

A tool to manage video input devices (mainly webcams).

Setup

• Install: apt install v4l-utils

Usage

• Show video devices:
  • List devices: v4l2-ctl --list-devices
  • Show brief device info: v4l2-ctl [-d <dev>] --info
  • Show extended device info: v4l2-ctl [-d <dev>] --all
  • Show device formats: v4l2-ctl [-d <dev>] --info --list-formats
  • Show device settings: v4l2-ctl [-d <dev>] --info --list-ctrls
  • If no device is specified, it defaults to /dev/video0.
  • Certain devices show up as multiple /dev/video* files. Typically there’s one video capture device and one metadata capture device. Use the command above to find out.
• Modify video device properties:
  • Show properties with min, max and current values: v4l2-ctl [-d <dev>] --all
  • Different webcams come with different properties and property names.
  • Change a property (non-permanent): v4l2-ctl [-d <dev>] -c <property>=<value>
  • Properties may be modified while the device is in use.
  • As property changes are not permanent, you may want to set them in a script or something.
  • Higher exposure may lead to reduced frame rate. To make it brighter you may increase the gain instead.
  • Focus and white balance can typically be left at auto. Brightness, contrast and saturation should typically be left at default.
  • Logitech C920 and similar:
    • Disable auto focus: focus_auto=0
    • Disable auto exposure: exposure_auto=1
    • Set exposure manually (after auto is disabled): exposure_absolute=250
    • Set gain: gain=250
    • Disable auto white balance: white_balance_temperature_auto=0
    • Set white balance manually (after auto is disabled): white_balance_temperature=4000
    • Set brightness, contrast and saturation (generally not needed): brightness=128, contrast=128, saturation=128

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