Rose of Jericho

Shortnote

Linux has quite a minimal support for video processing, even after decades of development it is difficult to find a software package that is seamlessly able to stream from a retail webcam. Amongst the software tried was:

  • ffmpeg and ffserver - even with the latest development branch, these two crash like there is no tomorrow, they either go out with segmentation fault, just die silently, bail out with indecipherable errors or just never work as they are supposed to.
  • vlc - aside the fact that it attempts to install (the other) half of the distribution in package dependencies, vlc seems good as a player but a horrible piece of rubbish when it comes to streaming. It either does not work, or you have to write a mile-long command line just to stream a webcam - not to mention that it wants transcode as well to convert formats.
  • motion - this looked promising, it worked once and then just stopped working for absolutely no reason.

The last one tried was fswebcam which, is not an ideal streaming software, but at least manages to snap a picture off the video device. One could mention that the infamous crap linux kernel needs to be upgraded as well, otherwise some webcams do not manage to snap at high resolutions, corrupting the image in the process. As it would be expected from Linux, instead of being able to perform a straight-forward task, you end up having to recompile the kernel.

So the way to go has been to use jQuery and AJAX in order to seamlessly refresh a static image once it changes while polling every 1s for changes. This is similar to the collaborative coding idea, just easier to accomplish.

Overview

Setup

  • Create a user for fswebcam and give it the appropriate permissions to be able to dump a jpeg in a folder accessible by the webserver.
  • Create a HTML file using the provided template below (note that the image being refreshed is called jericho.jpg, you can change this to whatever it has to be).
  • Create /etc/init.d/fswebcam on a debian system and run update-rc.d fswebcam defaults in order to make the script start on boot.

Rose of Jericho

Also known as Selaginella Lepidophylla, and easily confused with Anastatica, the Rose of Jericho is a plant classified by ITIS as:

+- Kingdom - Plantae - plantes, Planta, Vegetal, plants
+-- Subkingdom - Viridaeplantae  - green plants
+--- Infrakingdom - Streptophyta - land plants
+---- Division - Tracheophyta - vascular plants, tracheophytes
+----- Subdivision - Pteridophytina - pteridophytes, pteridófita
+------ Class - Lycopodiopsida
+------- Subclass - Lycopodiidae
+-------- Order - Selaginellales - spikemosses
+--------- Family - Selaginellaceae
+---------- Genus - Selaginella P. Beauv. - lesser clubmoss, spikemoss
+----------- Species - Selaginella lepidophylla (Hook. & Grev.) Spring - flower of stone

On of its outstanding qualities is that it manages to survive in the harshest of environments. When there is no water available, it curls up into a ball and waits for the wind to blow it away and when it touches water it opens up. Remarkable perhaps, is the speed with which it curls up and unfolds, which can be observed in real-time, without needing to cameras to fast-forward the process. The unfolding process lasts somewhere between 30m and 1h30m.

It is classified by NatureServe as G4, apparently secure and not at risk of extinction. Of course, with such resilience, it is unlikely that it will ever perish.

Lastly, it seems to drink a lot of water! :-)

Living Conditions

The Rose of Jericho likes the sun and plenty of water, it is placed in this experiment in an aluminum basket, with a light-collimator pointing on top of it. The aluminum basket is meant to reflect the light back onto the rose and the collimator is made by wrapping a low-powered neon bulb in aluminum foil in order to concentrate the beam at the rose.

Since the bulb may burst, given the wrapping, a fan is placed in the background to cool down the setup. This also funnels more air to the rose.

Index


web/webcam_streaming.txt · Last modified: 2022/04/19 08:28 by 127.0.0.1

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