Videoüberwachung mit Linux

Hardware

video4linux (V4L) devices

You need to install your camera with the right driver. It is out of scope of this document to tell you how to do this and it depends on which type of camera.

Once installed the camera(s) will have the device names /dev/video0, /dev/video1, /dev/video2...

FreeBSD has a different naming of devices. When you build Motion for FreeBSD the default device name is /dev/bktr0. Under FreeBSD a TV card has a special device for controlling the tuner (e.g. /dev/tuner0). The option tunerdevice is only valid when Motion is built and running under FreeBSD. For Linux do not include this option in the config file (remove or comment out).

USB cameras take a lot of bandwidth. A USB camera connected to a USB 1.1 port or hub consumes all the bandwidth. Even with a small framesize and low framerate you should not expect to have more than one camera per USB 1.1 controller. If you need more than 1 USB camera add extra USB PCI cards to your computer. There exists cards that have 4 inputs each with their own controller and with full bandwidth. Many 4-input cards only have 1 controller. USB cameras do not have the feature of selecting input channels. To disable the input selection the option input must be set to the value 8 for USB cameras.

Composite video cards are normally made with a chip called BT878 (older cards have a BT848). They all use the Linux driver called 'bttv'.

There are cards with more then one video input but still only one BT878 chip. They have a video multiplexer which input is selected with the config option input. Input channel numbers start at 0 (which is why the value 8 and not 0 disables input selection). There are video capture cards available with 4 or 8 inputs but only one chip. They present themselves as one single video device and you select input using the 'input' option. If you define e.g. 4 thread config files with the same videodevice name but different input numbers Motion automatically goes into round robin mode. See the round robin section for more information. Many TV tuner cards have the input channels: TV Tuner = 0, Standard composite video = 1, S-VHS = 3. Other have TV=0, composite video 1= 1, composite video = 2, S-VHS = 3. For video capture cards input 1 is normally the composite video input.

Some capture cards are specially made for surveillance with for example 4 inputs. Others have a TV tuner, a composite input (phono socket) and perhaps also a S-VHS input. For all these cards the inputs are numbered. The numbering varies from card to card so the easiest is to experiment for 5 minutes with a program that can show the videostream. Use a program such as Camstream or xawtv to experiment with the values.

If you use the TV tuner input you also need to set the frequency of the TV channel using the option frequency. Otherwise set 'frequency' to 0.

Finally you need to set the TV norm. Values: 0 (PAL), 1 (NTSC), 2 (SECAM), 3 (PAL NC no colour). Default is 0 (PAL). If your camera is a PAL black and white you may get a better result with norm=3 (PAL no colour).

If the netcam_url option is defined all the video4linux options are ignored so make sure the netcam_url option is commented out if you do not need it.

Software

• motion
  • Motion is a program that monitors the video signal from cameras. It is able to detect if a significant part of the picture has changed; in other words, it can detect motion.
• ZoneMinder
  • A full-featured, open source, state-of-the-art video surveillance software system.