V4L2.md

V4l2 device module

This page is updated to the 2.1 version

V4L2 module is the most generic device module for Galicaster. It is valid for devices and cards compatible with video4linux2 interface. For recommended devices, please check the list on right side of the screen. For more detailed information check out each device page or contact the Community spaces.

The V4L2 device module includes certain features:

• Cropping
• Mjpeg recording
• Framerate safeguard - to prevent dropped frames.

Module Compatibility

• UVC webcams -
  • We recommend Logitech c920, and CBC950.
  • List of UVC available devices
• Datapath RGB1Vision 1ES
  • Best used with datapath module
• Hauppauge PVR-350 and PVR-250
  • Best used with hauppauge module
• Epiphan frammegrabers
  • Best used with Epiphan module
• Bluecherry cards
• Osprey cards

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).
• file: The file name where the track will be recorded. (The path is automatically assembled)
• videocrop: Margin in pixels to be removed. 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.

Use GVUCView tool to know wich capabilities are compatible with your device

Caps

V4L2 devices accepts two types of signal inputs - RAW and MJPEG - and multiple resolution-framerate combinations. A simplified Gstreamer capabilities string is formed by type, resolution and framerate among other parameters:

• Type: image/jpeg | video/x-raw
• Framerate: X/Y. Examples: 30/1, 25/1, 24/1, 10/1
• Resolution: width=A,height=B. A and B being length in pixels Then, a complete caps string looks like:

image/jpeg, framerate=24/1, width=1280, height=720
video/x-raw, framerate=30/1, width=1280, height=1024

Examples:

For a Logitech c920

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

For a Datapath RGBVision e1s

[track1]
name = Slides
device = v4l2
location = /dev/screen
file = SCREEN.avi
flavor = presentation
caps = video/x-raw,framerate=30/1,width=1024,height=768