- <title>Idea for storing trusted timestamps in a Noark 5 archive</title>
- <link>http://people.skolelinux.org/pere/blog/Idea_for_storing_trusted_timestamps_in_a_Noark_5_archive.html</link>
- <guid isPermaLink="true">http://people.skolelinux.org/pere/blog/Idea_for_storing_trusted_timestamps_in_a_Noark_5_archive.html</guid>
- <pubDate>Wed, 7 Jun 2017 21:40:00 +0200</pubDate>
- <description><p><em>This is a copy of
-<a href="https://lists.nuug.no/pipermail/nikita-noark/2017-June/000297.html">an
-email I posted to the nikita-noark mailing list</a>. Please follow up
-there if you would like to discuss this topic. The background is that
-we are making a free software archive system based on the Norwegian
-<a href="https://www.arkivverket.no/forvaltning-og-utvikling/regelverk-og-standarder/noark-standarden">Noark
-5 standard</a> for government archives.</em></p>
-
-<p>I've been wondering a bit lately how trusted timestamps could be
-stored in Noark 5.
-<a href="https://en.wikipedia.org/wiki/Trusted_timestamping">Trusted
-timestamps</a> can be used to verify that some information
-(document/file/checksum/metadata) have not been changed since a
-specific time in the past. This is useful to verify the integrity of
-the documents in the archive.</p>
-
-<p>Then it occured to me, perhaps the trusted timestamps could be
-stored as dokument variants (ie dokumentobjekt referered to from
-dokumentbeskrivelse) with the filename set to the hash it is
-stamping?</p>
-
-<p>Given a "dokumentbeskrivelse" with an associated "dokumentobjekt",
-a new dokumentobjekt is associated with "dokumentbeskrivelse" with the
-same attributes as the stamped dokumentobjekt except these
-attributes:</p>
-
-<ul>
-
-<li>format -> "RFC3161"
-<li>mimeType -> "application/timestamp-reply"
-<li>formatDetaljer -> "&lt;source URL for timestamp service&gt;"
-<li>filenavn -> "&lt;sjekksum&gt;.tsr"
-
-</ul>
-
-<p>This assume a service following
-<a href="https://tools.ietf.org/html/rfc3161">IETF RFC 3161</a> is
-used, which specifiy the given MIME type for replies and the .tsr file
-ending for the content of such trusted timestamp. As far as I can
-tell from the Noark 5 specifications, it is OK to have several
-variants/renderings of a dokument attached to a given
-dokumentbeskrivelse objekt. It might be stretching it a bit to make
-some of these variants represent crypto-signatures useful for
-verifying the document integrity instead of representing the dokument
-itself.</p>
-
-<p>Using the source of the service in formatDetaljer allow several
-timestamping services to be used. This is useful to spread the risk
-of key compromise over several organisations. It would only be a
-problem to trust the timestamps if all of the organisations are
-compromised.</p>
-
-<p>The following oneliner on Linux can be used to generate the tsr
-file. $input is the path to the file to checksum, and $sha256 is the
-SHA-256 checksum of the file (ie the "<sjekksum>.tsr" value mentioned
-above).</p>
+ <title>Simple streaming the Linux desktop to Kodi using GStreamer and RTP</title>
+ <link>http://people.skolelinux.org/pere/blog/Simple_streaming_the_Linux_desktop_to_Kodi_using_GStreamer_and_RTP.html</link>
+ <guid isPermaLink="true">http://people.skolelinux.org/pere/blog/Simple_streaming_the_Linux_desktop_to_Kodi_using_GStreamer_and_RTP.html</guid>
+ <pubDate>Thu, 12 Jul 2018 17:55:00 +0200</pubDate>
+ <description><p>Last night, I wrote
+<a href="http://people.skolelinux.org/pere/blog/Streaming_the_Linux_desktop_to_Kodi_using_VLC_and_RTSP.html">a
+recipe to stream a Linux desktop using VLC to a instance of Kodi</a>.
+During the day I received valuable feedback, and thanks to the
+suggestions I have been able to rewrite the recipe into a much simpler
+approach requiring no setup at all. It is a single script that take
+care of it all.</p>
+
+<p>This new script uses GStreamer instead of VLC to capture the
+desktop and stream it to Kodi. This fixed the video quality issue I
+saw initially. It further removes the need to add a m3u file on the
+Kodi machine, as it instead connects to
+<a href="https://kodi.wiki/view/JSON-RPC_API/v8">the JSON-RPC API in
+Kodi</a> and simply ask Kodi to play from the stream created using
+GStreamer. Streaming the desktop to Kodi now become trivial. Copy
+the script below, run it with the DNS name or IP address of the kodi
+server to stream to as the only argument, and watch your screen show
+up on the Kodi screen. Note, it depend on multicast on the local
+network, so if you need to stream outside the local network, the
+script must be modified. Also note, I have no idea if audio work, as
+I only care about the picture part.</p>
+
+<blockquote><pre>
+#!/bin/sh
+#
+# Stream the Linux desktop view to Kodi. See
+# http://people.skolelinux.org/pere/blog/Streaming_the_Linux_desktop_to_Kodi_using_VLC_and_RTSP.html
+# for backgorund information.
+
+# Make sure the stream is stopped in Kodi and the gstreamer process is
+# killed if something go wrong (for example if curl is unable to find the
+# kodi server). Do the same when interrupting this script.
+kodicmd() {
+ host="$1"
+ cmd="$2"
+ params="$3"
+ curl --silent --header 'Content-Type: application/json' \
+ --data-binary "{ \"id\": 1, \"jsonrpc\": \"2.0\", \"method\": \"$cmd\", \"params\": $params }" \
+ "http://$host/jsonrpc"
+}
+cleanup() {
+ if [ -n "$kodihost" ] ; then
+ # Stop the playing when we end
+ playerid=$(kodicmd "$kodihost" Player.GetActivePlayers "{}" |
+ jq .result[].playerid)
+ kodicmd "$kodihost" Player.Stop "{ \"playerid\" : $playerid }" > /dev/null
+ fi
+ if [ "$gstpid" ] && kill -0 "$gstpid" >/dev/null 2>&1; then
+ kill "$gstpid"
+ fi
+}
+trap cleanup EXIT INT
+
+if [ -n "$1" ]; then
+ kodihost=$1
+ shift
+else
+ kodihost=kodi.local
+fi
+
+mcast=239.255.0.1
+mcastport=1234
+mcastttl=1
+
+pasrc=$(pactl list | grep -A2 'Source #' | grep 'Name: .*\.monitor$' | \
+ cut -d" " -f2|head -1)
+gst-launch-1.0 ximagesrc use-damage=0 ! video/x-raw,framerate=30/1 ! \
+ videoconvert ! queue2 ! \
+ x264enc bitrate=8000 speed-preset=superfast tune=zerolatency qp-min=30 \
+ key-int-max=15 bframes=2 ! video/x-h264,profile=high ! queue2 ! \
+ mpegtsmux alignment=7 name=mux ! rndbuffersize max=1316 min=1316 ! \
+ udpsink host=$mcast port=$mcastport ttl-mc=$mcastttl auto-multicast=1 sync=0 \
+ pulsesrc device=$pasrc ! audioconvert ! queue2 ! avenc_aac ! queue2 ! mux. \
+ > /dev/null 2>&1 &
+gstpid=$!
+
+# Give stream a second to get going
+sleep 1
+
+# Ask kodi to start streaming using its JSON-RPC API
+kodicmd "$kodihost" Player.Open \
+ "{\"item\": { \"file\": \"udp://@$mcast:$mcastport\" } }" > /dev/null
+
+# wait for gst to end
+wait "$gstpid"
+</pre></blockquote>
+
+<p>I hope you find the approach useful. I know I do.</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>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>PS: See
+<ahref="http://people.skolelinux.org/pere/blog/Simple_streaming_the_Linux_desktop_to_Kodi_using_GStreamer_and_RTP.html">the
+followup post</a> for a even better approach.</p>
+
+<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>
projects / homepage.git / blobdiff