Morphex's blogologue (Life, technology, music, politics, business, mental health and more)

This is the blog of Morten W. Petersen, aka. morphex in various places. I blog about my life, and what I find interesting and/or important. This is a personal blog without any editor or a lot of oversight so treat it as such. :)

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Taking a look at my Python surveil(lance) app

So, I created this surveillance app in Python, to surveil ( the room where I spend most of my time, just to make sure that nobody else visits it, without my approval.

Before I wrote this app, I saw there were different applications out there, that could do some sort of surveillance, but I guess I recognized early on that I could easily mail images to myself, and that this was a good approach as it kind of disconnects the surveil app from outside dependencies, at least it doesn't have to have an internet connection up absolutely all the time, to function.

Another feature of mailing myself images compiled into videos, is that as soon as it comes into (in my case) GMail's system, there is a record of the video, and it is because of that, difficult to manipulate data, when a mail has been delivered.

Python was the language of choice, because I wanted to make things easy for myself, and Python is the language I've worked with the most, and it is easy to read and write things in Python.

Before this, I had dabbled a bit with ffmpeg, playing around with videos, adding effects to them and so on.

I'd say fortunately I dabbled with ffmpeg, because it is quite a powerful video processing package. The command line is not intuitive and user friendly, but once the command line is right, ffmpeg seems to be pretty stable.

I read about Python and the GIL (Global Interpreter Lock) today, and I remember this from years back. I guess over 90% of the programming work I've done to date, is in Python and Zope 2. Zope 2 had a way around the GIL and exploiting all CPU cores, and that was running a main database server, and then having several database clients/applications on each of their on process, which effectively went around the GIL, as each application was one process to the operating system. This worked well as the system was built for few writes to the database and many reads.

So, fortunately I dabbled with ffmpeg before this project, because I soon realized that threading could be a bit of a headache, so I opted for running ffmpeg as a subprocess of the surveil app, and using shell scripting and files to pass messages; so when ffmpeg is done processing a set of images into a video, it creates a file, and a thread with a loop in the surveil app monitors for these files, then mails the video and deletes the files related to that video afterwards.

Python is simple and intuitive, and that's the main reason I think, that it became my programming language of choice. It was easy to get started, interesting to explore Python via the interpreter, and there was an advanced web system which used Python as the main programming language.

Years back, I was pretty much obsessed with cross-platform portability, but with this surveil app, I'm creating a temporary (RAM-based) file system which is Linux-specific, and I'd be happy if it runs on *nix/POSIX systems. It's all in keeping things simple.

So I guess the point of this post was to underline that, yes, Python has a GIL, but in most instances it is a non-issue, and if there are CPU-intensive things, these can be forked out to a command-line tool, or you could even have an extension in C which does the heavy lifting. If I hadn't learnt ffmpeg, I could easily have spent a lot more time writing this app.

Another point that is worth mentioning, is the file for this project, is easy to read, and goes with the Python style of simplicity, and goes one step beyond being a config file, it also has some (easy to understand) logic.

This project is a mix of different systems; Python to glue it all together, *nix file systems and scripting in a middle layer, and the ffmpeg application for the heavy-duty work. As far as I can tell, this is all good and stable, although the surveil app reboots about every 24 hours, so it is hard to know how well it runs with a 100% uptime.

[Permalink] [By morphex] [A surveillance app (Python tree here I come!) (Atom feed)] [23 Oct 15:26 Europe/Oslo]

Adding (mandatory) SMTP authentication to my surveil app

So, I was thinking a bit lately, about adding a small feature to my surveillance app, so that it would send a mail whenever it was started.

Went about to add that this evening, when I discovered that there were large gaps in time between mailed videos in my Surveillance folder/label.

After some searching and debugging, I found that the SMTP server (GMail's in this case), was rejecting emails from my IP. I guess that's just an automated response, when over time, I sent emails to myself,, from myself and at some point that gets flagged as spam, because I wasn't logged in before sending emails.

Anyway, I guess it was naive to try to run something without logging into an SMTP with spam being what it is, so I added (mandatory) support for logging into the outgoing SMTP server today.

In addition to this, I guess it is nice to have the ability to reboot the host regularly, as a host system might for some reason become bogged down. So I added a config option to specify the amount of time between each reboot, in

I think the config file is quite neat, because Python is neat; one can add config options, and even some logic to deal with config options in one file, and it seems natural.

At the end of the config file as it was on that commit, there is a statement that adds 5-60 minutes of delay to the reboot interval specified above - so that it is a bit harder to predict when a surveillance camera is rebooted.

[Permalink] [By morphex] [A surveillance app (Python tree here I come!) (Atom feed)] [15 Oct 00:57 Europe/Oslo]

Changes to my Python surveillance (webcam, web camera) app

So, I created a surveillance app a week ago, because I felt it would be comforting to be able to see if somebody had been into my room.

Since then, I had to make the mailer code, the codes that mails a compiled video to the given email address, a bit more robust:

As I one day discovered that the last mail sent to me with a video, was sent at 03:34, and looking at the log for surveil, I could see that DNS had stopped working.

Today I added another mailer feature, which is simply moving the mailer code into its own function, and then running that code as a loop forever, in a separate thread:

Other notable changes are a separate configuration file, as well as parsing the output from fswebcam when a picture is taken, and if an error is detected, re-get the image:

Finally, I added a script that can be started from Cron, so that the surveil app starts running as soon as the laptop/desktop/demoboard - whatever, boots up.

I added the script, because it's easy to forget to include the PATH etc. - which leads to confusion, irritation and so on, when automating things.

Of all the things I did summarized here, I think the mailer hack is the best; I simply moved some code around and fired up another thread, so that images are taken and videos created and mailed, without delays which could create gaps in time where the room was not surveilled.

[Permalink] [By morphex] [A surveillance app (Python tree here I come!) (Atom feed)] [24 Sep 15:01 Europe/Oslo]

A surveillance app (Python tree here I come!)

So, lately I've been taking it very easy on the activities front, since I've had a court-related matter to get to see the kids.

So I've had some ideas, urges etc. to do technical stuff, artsy stuff etc. - and today I wrote myself a script that will run on a PC, or a demo board like Raspberry Pi, Orange Pi etc. - and take pictures on a webcam, and merge these pictures taken over time into a video, and mail them.

I started with Python (2), but figured that now is the time to take the plunge to Python 3 and don't look back.

I have to say, Python 3 isn't difficult, there are some changes in conventions etc. but nothing big.

So I was able to be productive in Python 3 straight away, and wrote this script:

Which will do what I mentioned above. And here's the source code tree as it was when I wrote this post:

This video was generated from this script:

And impressively enough, each image the video was generated from, was 55-78 KB, while the entire video with 18 images was ~120 KB. I guess VP9 is effective at compressing, at the same time, a lot of the objects in the video are static.

[Permalink] [By morphex] [Python and web (Atom feed)] [17 Sep 00:08 Europe/Oslo]