Category: Computers

Welcome again!

Hi, and welcome back on my blog.

Following the progressive migration from epot.org to jepoirrier.net, you landed on the new address for my blog: http://www.jepoirrier.net/blog (new RSS feed here).

The migration process was easy, thanks to the WordPress eXtended RSS that contains posts, pages, comments, custom fields, categories, and tags. But there are two things left I wanted to keep: existing users and images which links are hard-coded in various posts.

For the links to images, I just replaced the old URL by the new one in VIM: :%s/old_path/new_path/g and voilà!

For the existing users, I just exported data from tables wp_users and wp_usermeta. So if you had an account on my previous blog (mandatory to post comments), you can use the same login and password! 🙂

Building on the move, I also changed links to more “sexy” permalink and allowed Gravatar for all comments (if you don’t have a gravatar, an identicon will be automatically generated for you).

One more thing to do: an automated redirection from the old pages/RSS to this one. I guess it would take the form of a HTTP 301 Redirection but I have still to automate the transformation of the 272 URLs …

See you here for the next post!

Photo credit: “We’ve moved” by Brian Gurrola on Flickr (CC-by-sa).

Using Mantis with a reduced mail() function

Mantis is a free web-based bug tracker. As most web trackers, it uses e-mail to notify testers and developers about the evolutions of issues they have reported or they just follow. For that purpose, Mantis uses Codeworx PHP Mailer class that gives you the opportunity to use the PHP mail() function, sendmail or a SMTP server to send those e-mails.

The use of the PHP mail() function is the default option. Unfortunately, some web hosting companies limits the PHP mail() function by forbidding the use of the 4th and 5th (optional) parameters. The result is that you can’t use the e-mail functionality of PHP mailer / Mantis because they use the 4th parameter.

The solution is to edit the file class.phpmailer.php in the directory mantis-dir/core/phpmailer/. Inside the file, look for the two lines containing the string “@mail” and replace the 4th argument by the e-mail address where the e-mail will be sent from. Example:

   $rt = @mail($to, $this->EncodeHeader($this->Subject), $body,
         "From: \"mybugs - Mantis bug tracker\" <me@domaine.tld>");
}
else
   $rt = @mail($to, $this->EncodeHeader($this->Subject), $body,
         "From: \"mybugs - Mantis bug tracker\" <me@domaine.tld>");

Now you have a fully functional bug tracker 🙂

FOSDEM 2009 and Gemvid 0.6c

This year, I only went for the Saturday afternoon session of FOSDEM 2009, the Free and Open Source software developers’ European Meeting. Two years ago, I mentioned the general trend that more women were interested in free/open source software/movement and this trend continues. But this time, I also noticed some really cute babies … and my son Neel-Alexandre was one of them of course! Although he’s only 7-month-old, he was really interested in the FreeBSD, Linux and Firefox mascots (respectively a red daemon, Tux the penguin and a fox). You are never too young to taste the truth 😉

I also gave a lightning talk about Gemvid, my solution to monitor rats general activity. I tried to explain most biological information needed to understand the principles and I think people were really interested in this software, something with an application a bit different than the previous talks. I updated the Gemvid website and I uploaded the latest revision (0.6c) that was “analysing” the audience from my laptop during the talk. Finally, I also uploaded the presentation (PDF, 1.3Mb) and you can directly see it below.

Non-invasive animal monitoring with Gemvidhttp://static.slideshare.net/swf/ssplayer2.swf?doc=090207gemvid-1234047158004992-1&rel=0&stripped_title=noninvasive-animal-monitoring-with-gemvid

View more presentations from jepoirrier. (tags: gemvid science)

See you next year, for the next version?

Baby movements during sleep

After a while, here is why I got a TV tuner for my Linux laptop, took screen captures and wrote a script to add a timestamp on pictures … I wanted to know how my (then 5-month-old) son was sleeping (his mom can be reassured: I was not planning to put electrodes on his scalp 😉 ).

Get the Flash Player to see this player.

var s1 = new SWFObject(“../videos/player.swf”,”ply”,”360″,”240″,”9″,”#FFFFFF”);
s1.addParam(“allowfullscreen”,”false”);
s1.addParam(“allowscriptaccess”,”sameDomain”);
s1.addParam(“flashvars”,”file=../videos/081129-night.flv&image=../videos/081129-night.jpg”);
s1.write(“container”);

Following this, I had interesting discussions with my dad about sleep patterns in babies. It could also be interesting to hybridize what we did for Gemvid and this simple solution in order to be able to quantify human/baby movements during sleep. My little knowledge of OpenCV can then come in handy for the motion and pattern detection …

Some additional technical details : Video was made from 321 TV screen captures (1 every 2 minutes) and played back at 1 frame per second. It was converted with FFmpeg (LGPL) and the Flash player is JW FLV Media Player (CC by-nc-sa). Ok: Flash is not free.

Awk oneliner to find a string in text files

If you want to know the name of files containing a special string, grep -c is your friend. But you also get names of files not containing your string (with count = 0). If you only want the names of files containing “mystring”, awk can help you:

grep -c "mystring" * | awk ' !/:0/ '

And if you don’t even want the number of times “mystring” appears (on 1 line):

grep -c "mystring" * | awk ' !/:0/ '| awk '{split($0, a, ":"); print a[1]}'

Any other ideas?

Short script to add a timestamp on pictures

Here is a short script (1.6kb) to add a timestamp on all PNG pictures in a directory. It requires Python and the Python Image Library (PIL). In order to use it, modify some parameters in the beginning to suit your needs (images directory, font file and size, etc.) and launch ./timestampFiles.py. Here is a before/after example (size of pictures is reduced to fit in this blog):

Before/after example of adding a timestamp to a picture

Note 1: the font is not included in the script. Here, I used FreeSans which is a true free font (GNU GPL with font exception). It is available here (local copy, just the FreeSans font, 753kb).

Note 2: I chose to convert PNG images to JPG ones for 2 reasons. First, my capture script gives me PNG images (see previous posts). Second, I want to be able to copy all JPG pictures in a MJPEG movie. It shouldn’t be difficult to change the different file formats to suit your needs (ask me if you can’t do that).

Note 3: I guess this would also have been possible using a bash script and imagemagick, Perl or any other programming language 😉

Taking automated screenshots from a live video camera

Following my previous post, I attached a video camera to the composite input of my tv tuner. One good thing I didn’t noticed yesterday is that mplayer can be told to directly use pvr:// as a source instead of the generic tv:// (with many options). So you just have to enter mplayer pvr:// -tv device=/dev/video1:input=0 in order to watch tv.

Noticed the input=0 above? This tells the tuner to take the video signal from the tv (read the mplayer man page to see how to change the channel). Now, since I connected my video camera to the composite video in, I need to tell mplayer to use it with input=1. One last thing: taking a screenshot in mplayer is done by pressing the ‘s’ key (with option -vf screenshot. In summary, the image below was taken with mplayer pvr:// -tv device=/dev/video1:input=1:noaudio -vo x11 -vf screenshot
 (camera facing the screen).

blurry capture of computer screen taken by camera connected to tv tuner

Now I want to take one screenshot every 5 seconds, even when I’m not there to press the ‘s’ key! For this purpose, we need to use a fifo file and mplayer in slave mode. Mplayer in slave mode will listen to commands we automatically send into the fifo file (by a different process, see below). This is how we do this:

mkfifo myfifofile.tmp
mplayer -slave -input file=myfifofile.tmp pvr:// -tv device=/dev/video1:input=1:noaudio -vo x11 -vf screenshot

And from another console, we can type echo "screenshot 0" >> myfifofile.tmp to take the screenshot. To automate all this, the following simple bash code is sufficient:

#!/bin/bash
# will send mplayer screenshot command every 5 seconds to fifo file
# stop this with Ctrl + C
LIMIT=0
while [ $LIMIT -lt 1 ]; do
echo "screenshot 0" >> myfifofile.tmp
sleep 5
done

In the end, stop the bash script with Ctrl + C and quit mplayer with echo "quit" >> myfifofile.tmp.

A first step toward TV on my Linux laptop

I recently got a Hauppauge WinTV-PVR-USB2 (a TV tuner, video recorder and FM receiver) because I read it was well supported on GNU/Linux. The following post explains how I installed it on a Fedora Core 9. If you want to install it with another Linux distribution, some information may vary but most of the following steps will be exactly the same.

First connect the USB device, the list of USB devices shows my system has recognised it:

[root@localhost ~]# lsusb
Bus 002 Device 003: ID 2040:2900 Hauppauge
...
[root@localhost ~]# dmesg
usbcore: registered new interface driver pvrusb2
pvrusb2: Hauppauge WinTV-PVR-USB2 MPEG2 Encoder/Tuner : V4L in-tree version
pvrusb2: Debug mask is 31 (0x1f)
firmware: requesting v4l-pvrusb2-29xxx-01.fw
pvrusb2: ***WARNING*** Device fx2 controller firmware seems to be missing.
pvrusb2: Did you install the pvrusb2 firmware files in their proper location?
pvrusb2: request_firmware unable to locate fx2 controller file v4l-pvrusb2-29xxx-01.fw
pvrusb2: Failure uploading firmware1
pvrusb2: Device initialization was not successful.
pvrusb2: Giving up since device microcontroller firmware appears to be missing.

Although my tuner is fully recognised, the system needs a firmware in order to make it work. Where is the firmware? A quick search on a well-known search engine redirects us to Mike Isely’s website where he explains how to get the driver (Mike actually also wrote the driver for this TV tuner). Although I got the CD with drivers for Windows, I prefer to use the latest driver that can be found on the Hauppage support website. Mike also writes you can get the driver from the ivtv project.

So I uncompress the driver in the “win_driver” directory and launch Mike Isely’s fwextract.pl script:

[jepoirrier@localhost hauppauge]$ mkdir win_driver
[jepoirrier@localhost hauppauge]$ unzip hauppauge_cd_3.4d1.zip -d win_driver/
[jepoirrier@localhost hauppauge]$ ./fwextract.pl

The script extracted 4 drivers (2 decoders and 2 encoders) and dmesg already told me the two I need: v4l-pvrusb2-29xxx-01.fw and v4l-cx2341x-enc.fw (as encoder). To know where to put these files, check a little bit on the web (this depends on your GNU/Linux distribution). On the Fedora Core 9, it’s in /lib/firmware, so:

[root@localhost hauppauge]# cp v4l-cx2341x-enc.fw /lib/firmware
[root@localhost hauppauge]# cp v4l-pvrusb2-29xxx-01.fw /lib/firmware

Unplug your USB cable, re-plug it and a dmesg should give you a long list of what your system detected, the most interesting part being the last line where it request the firmware and doesn’t stop: firmware: requesting v4l-cx2341x-enc.fw 🙂 Now check your video devices and you should have an additional /dev/videox:

[root@localhost hauppauge]# ls /dev/vid*
/dev/video /dev/video0 /dev/video1

In my case, /dev/video1 is the one I need …

Now, how to watch TV? TVTIME seems to be good but, unfortunately, my video card driver doesn’t support hardware YUY2 overlay (I have an ATI Radeon Mobility HD 2600 with the open source radeon driver). No problem: mplayer /dev/video1 shows a very beautiful snow. Now I need an antenna or a cable to connect to my tuner …

mplayer -vo x11 /dev/video1 -vf and then s

Pixel lapse under Linux

pixel-lapse under Linux

Finally, I got a working pixel lapse software under Linux 🙂 It’s a bit late (and I have to work tomorrow), code is rather dirty but I’ll publish it as soon as possible (btw that’s why I needed a webcam and a library to read it yesterday). Originally,

"pixel lapse" photography is the process of creating an image one pixel at a time. Beginning in the upper left corner, pixels are captured sequentially at a set rate until the entire image is formed.

Unfortunately, their software only runs on MacOS and Windows and requires Quicktime. Here, I "only" use OpenCV which is free and available under all the OS mentioned in this post. More details soon …

The “full-size” (640×480) image is here on Flickr

Edit on November 5th, 2008: version 0.1 of the software is available here.