Consturction timelapse project

crontab.conf

* 8-16 * * 1-5 ffmpeg -f video4linux2 -s 1920x1080 -i /dev/video0 -vframes 1 /home/kwyn/timelapse/$(date "-%Y-%m-%d_%H:%M:%S")-snapshot.jpeg

timelapse-notes.md

Webcam Timelapse Project

Need to take photos ever few minutes for the sake of creating a timelapse. I destroyed everything updating a graphics driver and learned my lesson for not keeping a lab notebooks for my side project. This is my second go around.

Configuring your webcam.

I have a logitech C920 HD webcam. After some sluthing on google I found the right utility package to use to control the webcam. sudo apt-get install v4l-utils You can find which devices exist by using v4l2-ctl --list-devices Once that's installed it's useful to list the controls available to my webcam v4l2-ctl -d /dev/video0 --list-ctrls

                     brightness 0x00980900 (int)    : min=0 max=255 step=1 default=128 value=128
                       contrast 0x00980901 (int)    : min=0 max=255 step=1 default=128 value=128
                     saturation 0x00980902 (int)    : min=0 max=255 step=1 default=128 value=128
 white_balance_temperature_auto 0x0098090c (bool)   : default=1 value=1
                           gain 0x00980913 (int)    : min=0 max=255 step=1 default=0 value=0
           power_line_frequency 0x00980918 (menu)   : min=0 max=2 default=2 value=2
      white_balance_temperature 0x0098091a (int)    : min=2000 max=6500 step=1 default=4000 value=4000 flags=inactive
                      sharpness 0x0098091b (int)    : min=0 max=255 step=1 default=128 value=128
         backlight_compensation 0x0098091c (int)    : min=0 max=1 step=1 default=0 value=0
                  exposure_auto 0x009a0901 (menu)   : min=0 max=3 default=3 value=3
              exposure_absolute 0x009a0902 (int)    : min=3 max=2047 step=1 default=250 value=250 flags=inactive
         exposure_auto_priority 0x009a0903 (bool)   : default=0 value=1
                   pan_absolute 0x009a0908 (int)    : min=-36000 max=36000 step=3600 default=0 value=0
                  tilt_absolute 0x009a0909 (int)    : min=-36000 max=36000 step=3600 default=0 value=0
                 focus_absolute 0x009a090a (int)    : min=0 max=250 step=5 default=0 value=0 flags=inactive
                     focus_auto 0x009a090c (bool)   : default=1 value=1
                  zoom_absolute 0x009a090d (int)    : min=100 max=500 step=1 default=100 value=100

I found that turning off all automatic utilities otherwise you get a weird flicker in the video as the camera constantly autofocuses

v4l2-ctl -d /dev/video0 --set-ctrl=exposure_auto=1
v4l2-ctl -d /dev/video0 --set-ctrl=focus_auto=0

Then I needed a thing to take photos with the camera ffmpeg seemed to be the best candidate for that. You can take a photo of a single still with this command ffmpeg -f video4linux2 -s 1920x1080 -i /dev/video0 -vframes 1 test.jpg So if we combined that with a cron job well, we have a timelapse capability on our hands don't we!

Oh but wait I need to be able to time stamp each file name... How can I do that? Well we can use Bash's ability to interpolate in comination with the built in bash date utility $(date "-%Y-%m-%d_%H:%M:%S")-snapshot

And this is a useful tutorial for stitching together the stills http://www.netinstructions.com/creating-automatic-timelapses-with-webcams-on-linux/