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Logitech webcams

This page is updated to the 2.0.0 release

Drivers & information

Logitech HD Webcams are compatible with Galicaster. They provide HD and Full HD videos. Other Logitech UVC webcams will work but most of them don't provide a fair resolution-framerate ratio.

Technical data

  • Vendor: Logitech
  • Models c920 and BCC950
  • Resolution: upto Full HD
  • Format: YUV or JPEG
  • Connector: USB 2.0
  • Signal: RAW
  • Drivers: pre-installed on Ubuntu 12
  • Plugin: v4l2
  • Price: around 100 €

Driver installation

The driver is included in the linux kernel - uvcvideo.

Device identification

  1. Find the Device name attribute:
  • udevadm info --attribute-walk --name=/dev/video0 | grep name
    • Usual Device IDs:
      • Logitech c910 on Ubuntu 16.04: UVC Camera (046d:0821)
  1. Fix access path
  • With sudo create or modify the file: /etc/udev/rules.d/galicaster.rules
  • Add the line: KERNEL=="video[0-9]*", ATTR{name}=="UVC Camera (046d:0821)", GROUP="video", SYMLINK+="logitech" Change ATTR{name} to the one obtained previously.

Device configuration

To probe the possible parameteres we recommend using guvcview, which will show the possible values to each parameter. Later, to fix the parameters use the video4linux2 CLI configuration and compound your configuration on a script:

To list the parameters:

  • v4l2-ctl -d /dev/video0 -L

Useful commands

  • Powerline frequency: v4l2-ctl -d /dev/logitech -c power_line_frequency=1 (1: 50 Hz 2: 60 Hz)
  • Autofocus: v4l2-ctl -d /dev/logitech -c focus_auto=1 (0:disable, 1:enable)
  • Exposure: v4l2-ctl -d /dev/logitech -c exposure_auto=0 (0:auto, 1:manual, 2:shutter, 3:aperture)

Module configuration

Admitted values:

  • name: Name assigned to the device.
  • device: Device type: v4l2
  • flavor: Matterhorn "flavor" associated to the track. (presenter|presentation|other)
  • location: Device's mount point in the system (e.g. /dev/video0 or /dev/logitech).
  • file: The file name where the track will be recorded. (default:CAMERA.avi)
  • videocrop: Margin in pixels to be cutted. Useful to set a 4:3 proportion on a HD webcam.videocrop-top, videocrop-bottom, videocrop-left, videocrop-right. (optional)
  • caps: GStreamer cappabilities of the device (mimetype=TYPE, framerate=X/Y,width=A,height=B)

Caps magic:

  • type: (image/jpeg | video/x-raw)
    • image/jpeg usually provides better framerate-resolution ratio, leaving de transcoding to the software
  • framerate: 24/1,25/1 or 30/1 for full motion 10/1 15/1 for testing.
  • resolution:
    • width=800,height=600, width=640,height=480, width=1024,height=768
    • panorarmic: width=1280,height=720 - width=1920,height=1080
  • Use guvcview to know wich capabilities are compatible with your device.

Example:

[track1]
name = Webcam
device = v4l2
flavor = presenter
location = /dev/logitech
file = WEBCAM.avi
caps = image/jpeg,framerate=24/1,width=1280,height=720
videocrop-left = 160
videocrop-right = 160

Troubleshooting

USB Amplifiers
USB amplifiers should be extended. Spirals along the wire will cause inductancy and thus damaging the signal Also, some USB extensors have been reported to fail occasionally.

FAQ

  1. Why is the preview jumpy?
  • The application may drop frames if is not capable of preview them fast enough. If the recording is jumpy too your computer may be not powerful enough capturing the video at the current framerate and resolution. Try lower parameters and close any other application that may affect CPU performance.
  1. Why is image is blurry?
  • This devices usually have autofocus cappabalities, set a custom focus and disable the autofocus.
  1. If I disconnect the webcam, will I lost the recording?
  • Most certainly, the system is very sensitive with USB devices so during a recording the device must remain plugged.
  1. I'm using an USB extensor but I'm getting errors.
  • USB wires can transmit information without losses up to 3 meters. To reach a longer distance you need a wire with an amplifier. There are amplified chords up to 20 meters. These chords should be fully extended, since inductancy can affect the signal.