autolapse

An automated octoprint timelapse generator

Concept

• The script polls the Octoprint API via localhost.
• It reads both the toolhead status and the job status.
• It uses the job status to extract the job name and create a target directory for the timelapse images.
• It uses the toolhead status to decide when to be active: It takes a snapshot via curl every 4 seconds as long as the head is above 120 °C.
• If curl fails, it calls the script "/home/pi/recam.sh" which restarts the webcamd service.

Motivation

• Octoprint's builtin timelapse stops at the end of the print file. Its post-roll option just appends the last picture, which usually is the print head still printing.
• By using the time delay of the print head cooling down, my script adds a generous amount of real post-roll pictures.

Prerequisites

• A working Octoprint installation
• An API key for getting access, which you'll need to enter in the ma_autolapse.sh file instead of "YOUR-API-KEY" (two locations in the file)
• A webcam connected to the Pi, whose output is accessible as JPEG still picture

Setup

• Add this start command to the /etc/rc.local file, above the final "exit 0" command:
• /home/pi/ma_autolapse.sh &
• Make sure that the script recam.sh runs without requiring the sudo password.

Hints, notes

• Octoprint 1.4 has changed the JSON output, rendering the previous Regexp used to extract the filename and progress invalid. Pick the right patterns for your Octoprint from the comments at the beginning of the ma_autolapse.sh file.
• Running the Raspberry off a USB SSD drive is highly recommended over using a microSD card, both for speed and durability.
• For best results, set the raspberry camera to fixed exposure and fixed white balance. This is accessible through the file /boot/octopi.txt
• My config line for the camera options reads like this:
• camera_raspi_options="-ev -2 -usestills -fps 2 -x 1920 -y 1080 -awb off --awbgainR 1.7 --awbgainB 1.5 -ex fixedfps -quality 50 -roi 0.2,0.2,0.6,0.6 "
  • "-ev 2" reduces the brightness. I have a black print bed, so the camera tends to overcompensate.
  • "-usestills" switches to still image mode. This improves picture quality over video mode (which compresses much stronger)
  • "-fps 2" reduces picture rate to 2 / second. Enough to see what's going on, less CPU required.
  • "-x 1920 -y 1080" use FullHD picture size
  • "-awb off --awbgainR 1.7 --awbgainB 1.5" locks the white balance. Green is always the reference at 1.0, Red and Blue are set to compensate the LED lighting I use.
  • "-ex fixedfps" sets the exposure mode.
  • "-quality 50" defines compression
  • "-roi 0.2,0.2,0.6,0.6" tells the camera to only use the center 60% of the sensor, with 20% offset to the left and top (basically zooming in a bit)