Source Repository for "Grüne Signale"
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green-signals is the source code for "Grüne Signale" digital signage solution.


"Grüne Signale" offers a digital signage platform intended for use in showrooms. Main goal is to run a slideshow presenting end-user customizable contents with low efforts and budget required to set it up.

  • Low Budget solution
  • Low Knowledge requirements
  • All based on OpenSource modules and OpenSource itself
  • Playback of Images and Videos (muted)
  • Media files can be delivered in nested folders
  • Playback of Media follows alpabetical order
  • Easy to configure
  • Easy content updates via media download (zipped)
  • Once set up it shall run unattended
  • Written in Python 3


  • Raspberry Pi computer with Power supply, HDMI cable and SD-Card
  • Display with HDMI input (best with HDMI CEC support)
  • this can be a dedicated computer monitor or a TV Set
  • the Display should support FullHD Resolution (native 1920x1080)
  • LAN or WLAN connection
  • Mouse and Keyboard only needed for initial setup
  • VLC Application (included in Full Raspian Image)
  • Python-VLC module (used for playback, installed from
  • Pillow module (used to scale down oversized images, installed from
  • requests module (used for downloading slideshow data, installed from
  • Cloud account for automated media update (we suggest to use "Grüne Wolke")
  • The media files need to be provided as ZIP-File containing the images and videos

Media formats

  • Images in JPG or PNG format, same display duration for all images as configured
  • Videos in MOV, M4V or MP4 format
  • All media shall have 16:9 landscape format
  • media with a different aspect ratio will show black borders
  • All media will be scaled to fill the screen
  • Best resolution is 1920x1080 pixels (FullHD)
  • images larger than 1920x1080 are scaled down after download, which is quite slow on the Raspberry Pi
  • Video clips are muted during playback
  • Video clips should start and end with blending from/to a black frame (playback could flicker)

Environmental Topics

  • A Raspberry Pi computer has low energy consumption (usually less than 10W)
  • It can be configured for a safe shut down at night time (reduce light pollution)
  • A diplay supporting HDMI CEC will automatically switch to StandBy
  • Power for Raspberry Pi and display shall be turned off by a timer device
  • set the timer a few minutes after scheduled shut down of the Raspberry Pi computer
  • when the power is switched back on in the morning, The slideshow will autoomatically start and in background update the media files

Development Environment

  • The project is developed on a Raspberry Pi 400, any Raspberry Pi model (except Pico) is fine
  • Raspberry Pi 1 and Zero models may partially work (limitatons with video playback)
  • The project is intended to run on "Raspberry Pi OS" (based on Debian Buster)
  • support for other platforms is possible, but not tested


  • create setup script (
  • run pip3 install python-vlc
  • run pip3 install python-crontab
  • add green-signals to auto-start
  • write configuration file
  • user friendly GUI
  • configuration script (included in
  • add cronjob for safe shutdown at given time (obsolete, handled internally)
  • validation that remote URL points to a ZIP file.
  • improve on-barding
  • so far only dummy images for intial slideshow
  • provide manual in media slides and as documentation (Wiki?)
  • tutorials and other on-boarding guides (maybe with "Grünstreifen")
  • testing, testing
  • and more testing in real world ;-)


Chatbegruenung, Channel netzbegruenung-digitalsignage Stefan Schmidt-Bilkenroth,