- <title>Easier recipe to observe the cell phones around you</title>
- <link>http://people.skolelinux.org/pere/blog/Easier_recipe_to_observe_the_cell_phones_around_you.html</link>
- <guid isPermaLink="true">http://people.skolelinux.org/pere/blog/Easier_recipe_to_observe_the_cell_phones_around_you.html</guid>
- <pubDate>Sun, 24 Sep 2017 08:30:00 +0200</pubDate>
- <description><p>A little more than a month ago I wrote
-<a href="http://people.skolelinux.org/pere/blog/Simpler_recipe_on_how_to_make_a_simple__7_IMSI_Catcher_using_Debian.html">how
-to observe the SIM card ID (aka IMSI number) of mobile phones talking
-to nearby mobile phone base stations using Debian GNU/Linux and a
-cheap USB software defined radio</a>, and thus being able to pinpoint
-the location of people and equipment (like cars and trains) with an
-accuracy of a few kilometer. Since then we have worked to make the
-procedure even simpler, and it is now possible to do this without any
-manual frequency tuning and without building your own packages.</p>
-
-<p>The <a href="https://tracker.debian.org/pkg/gr-gsm">gr-gsm</a>
-package is now included in Debian testing and unstable, and the
-IMSI-catcher code no longer require root access to fetch and decode
-the GSM data collected using gr-gsm.</p>
-
-<p>Here is an updated recipe, using packages built by Debian and a git
-clone of two python scripts:</p>
-
-<ol>
-
-<li>Start with a Debian machine running the Buster version (aka
- testing).</li>
-
-<li>Run '<tt>apt install gr-gsm python-numpy python-scipy
- python-scapy</tt>' as root to install required packages.</li>
-
-<li>Fetch the code decoding GSM packages using '<tt>git clone
- github.com/Oros42/IMSI-catcher.git</tt>'.</li>
-
-<li>Insert USB software defined radio supported by GNU Radio.</li>
-
-<li>Enter the IMSI-catcher directory and run '<tt>python
- scan-and-livemon</tt>' to locate the frequency of nearby base
- stations and start listening for GSM packages on one of them.</li>
-
-<li>Enter the IMSI-catcher directory and run '<tt>python
- simple_IMSI-catcher.py</tt>' to display the collected information.</li>
-
-</ol>
-
-<p>Note, due to a bug somewhere the scan-and-livemon program (actually
-<a href="https://github.com/ptrkrysik/gr-gsm/issues/336">its underlying
-program grgsm_scanner</a>) do not work with the HackRF radio. It do
-work with RTL 8232 and other similar USB radio receivers you can get
-very cheaply
-(<a href="https://www.ebay.com/sch/items/?_nkw=rtl+2832">for example
-from ebay</a>), so for now the solution is to scan using the RTL radio
-and only use HackRF for fetching GSM data.</p>
-
-<p>As far as I can tell, a cell phone only show up on one of the
-frequencies at the time, so if you are going to track and count every
-cell phone around you, you need to listen to all the frequencies used.
-To listen to several frequencies, use the --numrecv argument to
-scan-and-livemon to use several receivers. Further, I am not sure if
-phones using 3G or 4G will show as talking GSM to base stations, so
-this approach might not see all phones around you. I typically see
-0-400 IMSI numbers an hour when looking around where I live.</p>
-
-<p>I've tried to run the scanner on a
-<a href="https://wiki.debian.org/RaspberryPi">Raspberry Pi 2 and 3
-running Debian Buster</a>, but the grgsm_livemon_headless process seem
-to be too CPU intensive to keep up. When GNU Radio print 'O' to
-stdout, I am told there it is caused by a buffer overflow between the
-radio and GNU Radio, caused by the program being unable to read the
-GSM data fast enough. If you see a stream of 'O's from the terminal
-where you started scan-and-livemon, you need a give the process more
-CPU power. Perhaps someone are able to optimize the code to a point
-where it become possible to set up RPi3 based GSM sniffers? I tried
-using Raspbian instead of Debian, but there seem to be something wrong
-with GNU Radio on raspbian, causing glibc to abort().</p>
+ <title>Streaming the Linux desktop to Kodi using VLC and RTSP</title>
+ <link>http://people.skolelinux.org/pere/blog/Streaming_the_Linux_desktop_to_Kodi_using_VLC_and_RTSP.html</link>
+ <guid isPermaLink="true">http://people.skolelinux.org/pere/blog/Streaming_the_Linux_desktop_to_Kodi_using_VLC_and_RTSP.html</guid>
+ <pubDate>Thu, 12 Jul 2018 02:00:00 +0200</pubDate>
+ <description><p>A while back, I was asked by a friend how to stream the desktop to
+my projector connected to Kodi. I sadly had to admit that I had no
+idea, as it was a task I never had tried. Since then, I have been
+looking for a way to do so, preferable without much extra software to
+install on either side. Today I found a way that seem to kind of
+work. Not great, but it is a start.</p>
+
+<p>I had a look at several approaches, for example
+<a href="https://github.com/mfoetsch/dlna_live_streaming">using uPnP
+DLNA as described in 2011</a>, but it required a uPnP server, fuse and
+local storage enough to store the stream locally. This is not going
+to work well for me, lacking enough free space, and it would
+impossible for my friend to get working.</p>
+
+<p>Next, it occurred to me that perhaps I could use VLC to create a
+video stream that Kodi could play. Preferably using
+broadcast/multicast, to avoid having to change any setup on the Kodi
+side when starting such stream. Unfortunately, the only recipe I
+could find using multicast used the rtp protocol, and this protocol
+seem to not be supported by Kodi.</p>
+
+<p>On the other hand, the rtsp protocol is working! Unfortunately I
+have to specify the IP address of the streaming machine in both the
+sending command and the file on the Kodi server. But it is showing my
+desktop, and thus allow us to have a shared look on the big screen at
+the programs I work on.</p>
+
+<p>I did not spend much time investigating codeces. I combined the
+rtp and rtsp recipes from
+<a href="https://wiki.videolan.org/Documentation:Streaming_HowTo/Command_Line_Examples/">the
+VLC Streaming HowTo/Command Line Examples</a>, and was able to get
+this working on the desktop/streaming end.</p>
+
+<blockquote><pre>
+vlc screen:// --sout \
+ '#transcode{vcodec=mp4v,acodec=mpga,vb=800,ab=128}:rtp{dst=projector.local,port=1234,sdp=rtsp://192.168.11.4:8080/test.sdp}'
+</pre></blockquote>
+
+<p>I ssh-ed into my Kodi box and created a file like this with the
+same IP address:</p>
+
+<blockquote><pre>
+echo rtsp://192.168.11.4:8080/test.sdp \
+ > /storage/videos/screenstream.m3u
+</pre></blockquote>
+
+<p>Note the 192.168.11.4 IP address is my desktops IP address. As far
+as I can tell the IP must be hardcoded for this to work. In other
+words, if someone elses machine is going to do the steaming, you have
+to update screenstream.m4u on the Kodi machine and adjust the vlc
+recipe. To get started, locate the file in Kodi and select the m3u
+file while the VLC stream is running. The desktop then show up in my
+big screen. :)</p>
+
+<p>When using the same technique to stream a video file with audio,
+the audio quality is really bad. No idea if the problem is package
+loss or bad parameters for the transcode. I do not know VLC nor Kodi
+enough to tell.</p>
+
+<p><strong>Update 2018-07-12</strong>: Johannes Schauer send me a few
+succestions and reminded me about an important step. The "screen:"
+input source is only available once the vlc-plugin-access-extra
+package is installed on Debian. Without it, you will see this error
+message: "VLC is unable to open the MRL 'screen://'. Check the log
+for details." He further found that it is possible to drop some parts
+of the VLC command line to reduce the amount of hardcoded information.
+It is also useful to consider using cvlc to avoid having the VLC
+window in the desktop view. In sum, this give us this command line on
+the source end
+
+<blockquote><pre>
+cvlc screen:// --sout \
+ '#transcode{vcodec=mp4v,acodec=mpga,vb=800,ab=128}:rtp{sdp=rtsp://:8080/}'
+</pre></blockquote>
+
+<p>and this on the Kodi end<p>
+
+<blockquote><pre>
+echo rtsp://192.168.11.4:8080/ \
+ > /storage/videos/screenstream.m3u
+</pre></blockquote>
+
+<p>Still bad image quality, though. But I did discover that streaming
+a DVD using dvdsimple:///dev/dvd as the source had excellent video and
+audio quality, so I guess the issue is in the input or transcoding
+parts, not the rtsp part. I've tried to change the vb and ab
+parameters to use more bandwidth, but it did not make a
+difference.</p>
+
+<p>I further received a suggestion from Einar Haraldseid to try using
+gstreamer instead of VLC, and this proved to work great! He also
+provided me with the trick to get Kodi to use a multicast stream as
+its source. By using this monstrous oneliner, I can stream my desktop
+with good video quality in reasonable framerate to the 239.255.0.1
+multicast address on port 1234:
+
+<blockquote><pre>
+gst-launch-1.0 ximagesrc use-damage=0 ! video/x-raw,framerate=30/1 ! \
+ videoconvert ! queue2 ! \
+ x264enc bitrate=8000 speed-preset=superfast tune=zerolatency qp-min=30 \
+ key-int-max=15 bframes=2 ! video/x-h264,profile=high ! queue2 ! \
+ mpegtsmux alignment=7 name=mux ! rndbuffersize max=1316 min=1316 ! \
+ udpsink host=239.255.0.1 port=1234 ttl-mc=0 auto-multicast=1 sync=0 \
+ pulsesrc device=$(pactl list | grep -A2 'Source #' | \
+ grep 'Name: .*\.monitor$' | cut -d" " -f2|head -1) ! \
+ audioconvert ! queue2 ! avenc_aac ! queue2 ! mux.
+</pre></blockquote>
+
+<p>and this on the Kodi end<p>
+
+<blockquote><pre>
+echo udp://@239.255.0.1:1234 \
+ > /storage/videos/screenstream.m3u
+</pre></blockquote>
+
+<p>Note the trick to pick a valid pulseaudio source. It might not
+pick the one you need. This approach will of course lead to trouble
+if more than one source uses the same multicast port and address.
+Note the ttl-mc=0 setting, which limit the multicast packages to the
+local network. If the value is increased, your screen will be
+broadcasted further, one network "hop" for each increase (read up on
+multicast to learn more. :)!</p>
+
+<p>Having cracked how to get Kodi to receive multicast streams, I
+could use this VLC command to stream to the same multicast address.
+The image quality is way better than the rtsp approach.</p>
+
+<blockquote><pre>
+cvlc screen:// --sout '#transcode{vcodec=mp4v,acodec=mpga,vb=800,ab=128}:rtp{mux=ts,dst=239.255.0.1,port=1234,sdp=sap}'
+</pre></blockquote>
+
+<p>As usual, if you use Bitcoin and want to show your support of my
+activities, please send Bitcoin donations to my address
+<b><a href="bitcoin:15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b">15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b</a></b>.</p>