Let’s say you want to monitor a room and have a running linux machine(in our case ubuntu) with a webcam attached.

Problems that could appear:

• Recording continuously for a long period can result in extremely large video files, especially when uncompressed, and a pretty high CPU usage.
• In the case above you would have to compress and “logrotate” your video streams periodically
• Maybe you do not want to record anything if nothing happens

Our solution:

$ sudo apt-get install webcam


use the following configuration file (webcam.conf)


[grab]
device = /dev/video0
text = "my office %Y-%m-%d %H:%M:%S"
infofile = filename
fg_red = 255
fg_green = 255
fg_blue = 255
width = 320
height = 240
delay = 5
wait = 0
rotate = 0
top = 0
left = 0
bottom = -1
right = -1
quality = 80
trigger = 175
once = 0
archive = take %Y-%m-%d %H:%M:%S

[ftp]
dir = /path/to/images/temp
file = webcam_l.jpeg
tmp = uploading_l.jpeg
passive = 0
debug = 0
auto = 0
local = 1
ssh = 0


And now run


$ webcam webcam.conf &


Now you will get a JPG image from your webcam (quality = 80) every 5 seconds (delay = 5) but only if something changed. The “something changed”-condition is given by the setting trigger = 175.