- <title>A program should be able to open its own files on Linux</title>
- <link>http://people.skolelinux.org/pere/blog/A_program_should_be_able_to_open_its_own_files_on_Linux.html</link>
- <guid isPermaLink="true">http://people.skolelinux.org/pere/blog/A_program_should_be_able_to_open_its_own_files_on_Linux.html</guid>
- <pubDate>Sun, 5 Jun 2016 08:30:00 +0200</pubDate>
- <description><p>Many years ago, when koffice was fresh and with few users, I
-decided to test its presentation tool when making the slides for a
-talk I was giving for NUUG on Japhar, a free Java virtual machine. I
-wrote the first draft of the slides, saved the result and went to bed
-the day before I would give the talk. The next day I took a plane to
-the location where the meeting should take place, and on the plane I
-started up koffice again to polish the talk a bit, only to discover
-that kpresenter refused to load its own data file. I cursed a bit and
-started making the slides again from memory, to have something to
-present when I arrived. I tested that the saved files could be
-loaded, and the day seemed to be rescued. I continued to polish the
-slides until I suddenly discovered that the saved file could no longer
-be loaded into kpresenter. In the end I had to rewrite the slides
-three times, condensing the content until the talk became shorter and
-shorter. After the talk I was able to pinpoint the problem &ndash;
-kpresenter wrote inline images in a way itself could not understand.
-Eventually that bug was fixed and kpresenter ended up being a great
-program to make slides. The point I'm trying to make is that we
-expect a program to be able to load its own data files, and it is
-embarrassing to its developers if it can't.</p>
-
-<p>Did you ever experience a program failing to load its own data
-files from the desktop file browser? It is not a uncommon problem. A
-while back I discovered that the screencast recorder
-gtk-recordmydesktop would save an Ogg Theora video file the KDE file
-browser would refuse to open. No video player claimed to understand
-such file. I tracked down the cause being <tt>file --mime-type</tt>
-returning the application/ogg MIME type, which no video player I had
-installed listed as a MIME type they would understand. I asked for
-<a href="http://bugs.gw.com/view.php?id=382">file to change its
-behavour</a> and use the MIME type video/ogg instead. I also asked
-several video players to add video/ogg to their desktop files, to give
-the file browser an idea what to do about Ogg Theora files. After a
-while, the desktop file browsers in Debian started to handle the
-output from gtk-recordmydesktop properly.</p>
-
-<p>But history repeats itself. A few days ago I tested the music
-system Rosegarden again, and I discovered that the KDE and xfce file
-browsers did not know what to do with the Rosegarden project files
-(*.rg). I've reported <a href="http://bugs.debian.org/825993">the
-rosegarden problem to BTS</a> and a fix is commited to git and will be
-included in the next upload. To increase the chance of me remembering
-how to fix the problem next time some program fail to load its files
-from the file browser, here are some notes on how to fix it.</p>
-
-<p>The file browsers in Debian in general operates on MIME types.
-There are two sources for the MIME type of a given file. The output from
-<tt>file --mime-type</tt> mentioned above, and the content of the
-shared MIME type registry (under /usr/share/mime/). The file MIME
-type is mapped to programs supporting the MIME type, and this
-information is collected from
-<a href="https://www.freedesktop.org/wiki/Specifications/desktop-entry-spec/">the
-desktop files</a> available in /usr/share/applications/. If there is
-one desktop file claiming support for the MIME type of the file, it is
-activated when asking to open a given file. If there are more, one
-can normally select which one to use by right-clicking on the file and
-selecting the wanted one using 'Open with' or similar. In general
-this work well. But it depend on each program picking a good MIME
-type (preferably
-<a href="http://www.iana.org/assignments/media-types/media-types.xhtml">a
-MIME type registered with IANA</a>), file and/or the shared MIME
-registry recognizing the file and the desktop file to list the MIME
-type in its list of supported MIME types.</p>
-
-<p>The <tt>/usr/share/mime/packages/rosegarden.xml</tt> entry for
-<a href="http://www.freedesktop.org/wiki/Specifications/shared-mime-info-spec">the
-Shared MIME database</a> look like this:</p>
-
-<p><blockquote><pre>
-&lt;?xml version="1.0" encoding="UTF-8"?&gt;
-&lt;mime-info xmlns="http://www.freedesktop.org/standards/shared-mime-info"&gt;
- &lt;mime-type type="audio/x-rosegarden"&gt;
- &lt;sub-class-of type="application/x-gzip"/&gt;
- &lt;comment&gt;Rosegarden project file&lt;/comment&gt;
- &lt;glob pattern="*.rg"/&gt;
- &lt;/mime-type&gt;
-&lt;/mime-info&gt;
-</pre></blockquote></p>
-
-<p>This states that audio/x-rosegarden is a kind of application/x-gzip
-(it is a gzipped XML file). Note, it is much better to use an
-official MIME type registered with IANA than it is to make up ones own
-unofficial ones like the x-rosegarden type used by rosegarden.</p>
-
-<p>The desktop file of the rosegarden program failed to list
-audio/x-rosegarden in its list of supported MIME types, causing the
-file browsers to have no idea what to do with *.rg files:</p>
-
-<p><blockquote><pre>
-% grep Mime /usr/share/applications/rosegarden.desktop
-MimeType=audio/x-rosegarden-composition;audio/x-rosegarden-device;audio/x-rosegarden-project;audio/x-rosegarden-template;audio/midi;
-X-KDE-NativeMimeType=audio/x-rosegarden-composition
-%
-</pre></blockquote></p>
-
-<p>The fix was to add "audio/x-rosegarden;" at the end of the
-MimeType= line.</p>
-
-<p>If you run into a file which fail to open the correct program when
-selected from the file browser, please check out the output from
-<tt>file --mime-type</tt> for the file, ensure the file ending and
-MIME type is registered somewhere under /usr/share/mime/ and check
-that some desktop file under /usr/share/applications/ is claiming
-support for this MIME type. If not, please report a bug to have it
-fixed. :)</p>
+ <title>Visualizing GSM radio chatter using gr-gsm and Hopglass</title>
+ <link>http://people.skolelinux.org/pere/blog/Visualizing_GSM_radio_chatter_using_gr_gsm_and_Hopglass.html</link>
+ <guid isPermaLink="true">http://people.skolelinux.org/pere/blog/Visualizing_GSM_radio_chatter_using_gr_gsm_and_Hopglass.html</guid>
+ <pubDate>Fri, 29 Sep 2017 10:30:00 +0200</pubDate>
+ <description><p>Every mobile phone announce its existence over radio to the nearby
+mobile cell towers. And this radio chatter is available for anyone
+with a radio receiver capable of receiving them. Details about the
+mobile phones with very good accuracy is of course collected by the
+phone companies, but this is not the topic of this blog post. The
+mobile phone radio chatter make it possible to figure out when a cell
+phone is nearby, as it include the SIM card ID (IMSI). By paying
+attention over time, one can see when a phone arrive and when it leave
+an area. I believe it would be nice to make this information more
+available to the general public, to make more people aware of how
+their phones are announcing their whereabouts to anyone that care to
+listen.</p>
+
+<p>I am very happy to report that we managed to get something
+visualizing this information up and running for
+<a href="http://norwaymakers.org/osf17">Oslo Skaperfestival 2017</a>
+(Oslo Makers Festival) taking place today and tomorrow at Deichmanske
+library. The solution is based on the
+<a href="http://people.skolelinux.org/pere/blog/Easier_recipe_to_observe_the_cell_phones_around_you.html">simple
+recipe for listening to GSM chatter</a> I posted a few days ago, and
+will show up at the stand of <a href="http://sonen.ifi.uio.no/">Åpen
+Sone from the Computer Science department of the University of
+Oslo</a>. The presentation will show the nearby mobile phones (aka
+IMSIs) as dots in a web browser graph, with lines to the dot
+representing mobile base station it is talking to. It was working in
+the lab yesterday, and was moved into place this morning.</p>
+
+<p>We set up a fairly powerful desktop machine using Debian
+Buster/Testing with several (five, I believe) RTL2838 DVB-T receivers
+connected and visualize the visible cell phone towers using an
+<a href="https://github.com/marlow925/hopglass">English version of
+Hopglass</a>. A fairly powerfull machine is needed as the
+grgsm_livemon_headless processes from
+<a href="https://tracker.debian.org/pkg/gr-gsm">gr-gsm</a> converting
+the radio signal to data packages is quite CPU intensive.</p>
+
+<p>The frequencies to listen to, are identified using a slightly
+patched scan-and-livemon (to set the --args values for each receiver),
+and the Hopglass data is generated using the
+<a href="https://github.com/petterreinholdtsen/IMSI-catcher/tree/meshviewer-output">patches
+in my meshviewer-output branch</a>. For some reason we could not get
+more than four SDRs working. There is also a geographical map trying
+to show the location of the base stations, but I believe their
+coordinates are hardcoded to some random location in Germany, I
+believe. The code should be replaced with code to look up location in
+a text file, a sqlite database or one of the online databases
+mentioned in
+<a href="https://github.com/Oros42/IMSI-catcher/issues/14">the github
+issue for the topic</a>.
+
+<p>If this sound interesting, visit the stand at the festival!</p>
projects / homepage.git / blobdiff