+ <item>
+ <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.m3u 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=1 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=1 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, but gstreamer
+seem to be doing a better job.</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>
+</description>
+ </item>
+
+ <item>
+ <title>What is the most supported MIME type in Debian in 2018?</title>
+ <link>http://people.skolelinux.org/pere/blog/What_is_the_most_supported_MIME_type_in_Debian_in_2018_.html</link>
+ <guid isPermaLink="true">http://people.skolelinux.org/pere/blog/What_is_the_most_supported_MIME_type_in_Debian_in_2018_.html</guid>
+ <pubDate>Mon, 9 Jul 2018 08:05:00 +0200</pubDate>
+ <description><p>Five years ago,
+<a href="http://people.skolelinux.org/pere/blog/What_is_the_most_supported_MIME_type_in_Debian_.html">I
+measured what the most supported MIME type in Debian was</a>, by
+analysing the desktop files in all packages in the archive. Since
+then, the DEP-11 AppStream system has been put into production, making
+the task a lot easier. This made me want to repeat the measurement,
+to see how much things changed. Here are the new numbers, for
+unstable only this time:
+
+<p><strong>Debian Unstable:</strong></p>
+
+<pre>
+ count MIME type
+ ----- -----------------------
+ 56 image/jpeg
+ 55 image/png
+ 49 image/tiff
+ 48 image/gif
+ 39 image/bmp
+ 38 text/plain
+ 37 audio/mpeg
+ 34 application/ogg
+ 33 audio/x-flac
+ 32 audio/x-mp3
+ 30 audio/x-wav
+ 30 audio/x-vorbis+ogg
+ 29 image/x-portable-pixmap
+ 27 inode/directory
+ 27 image/x-portable-bitmap
+ 27 audio/x-mpeg
+ 26 application/x-ogg
+ 25 audio/x-mpegurl
+ 25 audio/ogg
+ 24 text/html
+</pre>
+
+<p>The list was created like this using a sid chroot: "cat
+/var/lib/apt/lists/*sid*_dep11_Components-amd64.yml.gz| zcat | awk '/^
+- \S+\/\S+$/ {print $2 }' | sort | uniq -c | sort -nr | head -20"</p>
+
+<p>It is interesting to see how image formats have passed text/plain
+as the most announced supported MIME type. These days, thanks to the
+AppStream system, if you run into a file format you do not know, and
+want to figure out which packages support the format, you can find the
+MIME type of the file using "file --mime &lt;filename&gt;", and then
+look up all packages announcing support for this format in their
+AppStream metadata (XML or .desktop file) using "appstreamcli
+what-provides mimetype &lt;mime-type&gt;. For example if you, like
+me, want to know which packages support inode/directory, you can get a
+list like this:</p>
+
+<p><blockquote><pre>
+% appstreamcli what-provides mimetype inode/directory | grep Package: | sort
+Package: anjuta
+Package: audacious
+Package: baobab
+Package: cervisia
+Package: chirp
+Package: dolphin
+Package: doublecmd-common
+Package: easytag
+Package: enlightenment
+Package: ephoto
+Package: filelight
+Package: gwenview
+Package: k4dirstat
+Package: kaffeine
+Package: kdesvn
+Package: kid3
+Package: kid3-qt
+Package: nautilus
+Package: nemo
+Package: pcmanfm
+Package: pcmanfm-qt
+Package: qweborf
+Package: ranger
+Package: sirikali
+Package: spacefm
+Package: spacefm
+Package: vifm
+%
+</pre></blockquote></p>
+
+<p>Using the same method, I can quickly discover that the Sketchup file
+format is not yet supported by any package in Debian:</p>
+
+<p><blockquote><pre>
+% appstreamcli what-provides mimetype application/vnd.sketchup.skp
+Could not find component providing 'mimetype::application/vnd.sketchup.skp'.
+%
+</pre></blockquote></p>
+
+<p>Yesterday I used it to figure out which packages support the STL 3D
+format:</p>
+
+<p><blockquote><pre>
+% appstreamcli what-provides mimetype application/sla|grep Package
+Package: cura
+Package: meshlab
+Package: printrun
+%
+</pre></blockquote></p>
+
+<p>PS: A new version of Cura was uploaded to Debian yesterday.</p>
+
+<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>
+</description>
+ </item>
+
+ <item>
+ <title>Debian APT upgrade without enough free space on the disk...</title>
+ <link>http://people.skolelinux.org/pere/blog/Debian_APT_upgrade_without_enough_free_space_on_the_disk___.html</link>
+ <guid isPermaLink="true">http://people.skolelinux.org/pere/blog/Debian_APT_upgrade_without_enough_free_space_on_the_disk___.html</guid>
+ <pubDate>Sun, 8 Jul 2018 12:10:00 +0200</pubDate>
+ <description><p>Quite regularly, I let my Debian Sid/Unstable chroot stay untouch
+for a while, and when I need to update it there is not enough free
+space on the disk for apt to do a normal 'apt upgrade'. I normally
+would resolve the issue by doing 'apt install &lt;somepackages&gt;' to
+upgrade only some of the packages in one batch, until the amount of
+packages to download fall below the amount of free space available.
+Today, I had about 500 packages to upgrade, and after a while I got
+tired of trying to install chunks of packages manually. I concluded
+that I did not have the spare hours required to complete the task, and
+decided to see if I could automate it. I came up with this small
+script which I call 'apt-in-chunks':</p>
+
+<p><blockquote><pre>
+#!/bin/sh
+#
+# Upgrade packages when the disk is too full to upgrade every
+# upgradable package in one lump. Fetching packages to upgrade using
+# apt, and then installing using dpkg, to avoid changing the package
+# flag for manual/automatic.
+
+set -e
+
+ignore() {
+ if [ "$1" ]; then
+ grep -v "$1"
+ else
+ cat
+ fi
+}
+
+for p in $(apt list --upgradable | ignore "$@" |cut -d/ -f1 | grep -v '^Listing...'); do
+ echo "Upgrading $p"
+ apt clean
+ apt install --download-only -y $p
+ for f in /var/cache/apt/archives/*.deb; do
+ if [ -e "$f" ]; then
+ dpkg -i /var/cache/apt/archives/*.deb
+ break
+ fi
+ done
+done
+</pre></blockquote></p>
+
+<p>The script will extract the list of packages to upgrade, try to
+download the packages needed to upgrade one package, install the
+downloaded packages using dpkg. The idea is to upgrade packages
+without changing the APT mark for the package (ie the one recording of
+the package was manually requested or pulled in as a dependency). To
+use it, simply run it as root from the command line. If it fail, try
+'apt install -f' to clean up the mess and run the script again. This
+might happen if the new packages conflict with one of the old
+packages. dpkg is unable to remove, while apt can do this.</p>
+
+<p>It take one option, a package to ignore in the list of packages to
+upgrade. The option to ignore a package is there to be able to skip
+the packages that are simply too large to unpack. Today this was
+'ghc', but I have run into other large packages causing similar
+problems earlier (like TeX).</p>
+
+<p>Update 2018-07-08: Thanks to Paul Wise, I am aware of two
+alternative ways to handle this. The "unattended-upgrades
+--minimal-upgrade-steps" option will try to calculate upgrade sets for
+each package to upgrade, and then upgrade them in order, smallest set
+first. It might be a better option than my above mentioned script.
+Also, "aptutude upgrade" can upgrade single packages, thus avoiding
+the need for using "dpkg -i" in the script above.</p>
+
+<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>
+</description>
+ </item>
+
+ <item>
+ <title>The worlds only stone power plant?</title>
+ <link>http://people.skolelinux.org/pere/blog/The_worlds_only_stone_power_plant_.html</link>
+ <guid isPermaLink="true">http://people.skolelinux.org/pere/blog/The_worlds_only_stone_power_plant_.html</guid>
+ <pubDate>Sat, 30 Jun 2018 10:35:00 +0200</pubDate>
+ <description><p>So far, at least hydro-electric power, coal power, wind power,
+solar power, and wood power are well known. Until a few days ago, I
+had never heard of stone power. Then I learn about a quarry in a
+mountain in
+<a href="https://en.wikipedia.org/wiki/Bremanger">Bremanger</a> i
+Norway, where
+<a href="https://www.bontrup.com/en/activities/raw-materials/bremanger-quarry/">the
+Bremanger Quarry</a> company is extracting stone and dumping the stone
+into a shaft leading to its shipping harbour. This downward movement
+in this shaft is used to produce electricity. In short, it is using
+falling rocks instead of falling water to produce electricity, and
+according to its own statements it is producing more power than it is
+using, and selling the surplus electricity to the Norwegian power
+grid. I find the concept truly amazing. Is this the worlds only
+stone power plant?</p>
+
+<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>
+</description>
+ </item>
+
projects / homepage.git / blobdiff