<link>http://people.skolelinux.org/pere/blog/</link>
<atom:link href="http://people.skolelinux.org/pere/blog/index.rss" rel="self" type="application/rss+xml" />
+ <item>
+ <title>Time for an official MIME type for patches?</title>
+ <link>http://people.skolelinux.org/pere/blog/Time_for_an_official_MIME_type_for_patches_.html</link>
+ <guid isPermaLink="true">http://people.skolelinux.org/pere/blog/Time_for_an_official_MIME_type_for_patches_.html</guid>
+ <pubDate>Thu, 1 Nov 2018 08:15:00 +0100</pubDate>
+ <description><p>As part of my involvement in
+<a href="https://gitlab.com/OsloMet-ABI/nikita-noark5-core">the Nikita
+archive API project</a>, I've been importing a fairly large lump of
+emails into a test instance of the archive to see how well this would
+go. I picked a subset of <a href="https://notmuchmail.org/">my
+notmuch email database</a>, all public emails sent to me via
+@lists.debian.org, giving me a set of around 216 000 emails to import.
+In the process, I had a look at the various attachments included in
+these emails, to figure out what to do with attachments, and noticed
+that one of the most common attachment formats do not have
+<a href="https://www.iana.org/assignments/media-types/media-types.xhtml">an
+official MIME type</a> registered with IANA/IETF. The output from
+diff, ie the input for patch, is on the top 10 list of formats
+included in these emails. At the moment people seem to use either
+text/x-patch or text/x-diff, but neither is officially registered. It
+would be better if one official MIME type were registered and used
+everywhere.</p>
+
+<p>To try to get one official MIME type for these files, I've brought
+up the topic on
+<a href="https://www.ietf.org/mailman/listinfo/media-types">the
+media-types mailing list</a>. If you are interested in discussion
+which MIME type to use as the official for patch files, or involved in
+making software using a MIME type for patches, perhaps you would like
+to join the discussion?</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>Measuring the speaker frequency response using the AUDMES free software GUI - nice free software</title>
+ <link>http://people.skolelinux.org/pere/blog/Measuring_the_speaker_frequency_response_using_the_AUDMES_free_software_GUI___nice_free_software.html</link>
+ <guid isPermaLink="true">http://people.skolelinux.org/pere/blog/Measuring_the_speaker_frequency_response_using_the_AUDMES_free_software_GUI___nice_free_software.html</guid>
+ <pubDate>Mon, 22 Oct 2018 08:40:00 +0200</pubDate>
+ <description><p><img src="http://people.skolelinux.org/pere/blog/images/2018-10-22-audmes-measure-speakers.png" align="right" width="40%"/></p>
+
+<p>My current home stereo is a patchwork of various pieces I got on
+flee markeds over the years. It is amazing what kind of equipment
+show up there. I've been wondering for a while if it was possible to
+measure how well this equipment is working together, and decided to
+see how far I could get using free software. After trawling the web I
+came across an article from DIY Audio and Video on
+<a href="https://www.diyaudioandvideo.com/Tutorial/SpeakerResponseTesting/">Speaker
+Testing and Analysis</a> describing how to test speakers, and it listing
+several software options, among them
+<a href="https://sourceforge.net/projects/audmes/">AUDio MEasurement
+System (AUDMES)</a>. It is the only free software system I could find
+focusing on measuring speakers and audio frequency response. In the
+process I also found an interesting article from NOVO on
+<a href="http://novo.press/understanding-speaker-specifications-and-frequency-response/">Understanding
+Speaker Specifications and Frequency Response</a> and an article from
+ecoustics on
+<a href="https://www.ecoustics.com/articles/understanding-speaker-frequency-response/">Understanding
+Speaker Frequency Response</a>, with a lot of information on what to
+look for and how to interpret the graphs. Armed with this knowledge,
+I set out to measure the state of my speakers.</p>
+
+<p>The first hurdle was that AUDMES hadn't seen a commit for 10 years
+and did not build with current compilers and libraries. I got in
+touch with its author, who no longer was spending time on the program
+but gave me write access to the subversion repository on Sourceforge.
+The end result is that now the code build on Linux and is capable of
+saving and loading the collected frequency response data in CSV
+format. The application is quite nice and flexible, and I was able to
+select the input and output audio interfaces independently. This made
+it possible to use a USB mixer as the input source, while sending
+output via my laptop headphone connection. I lacked the hardware and
+cabling to figure out a different way to get independent cabling to
+speakers and microphone.</p>
+
+<p>Using this setup I could see how a large range of high frequencies
+apparently were not making it out of my speakers. The picture show
+the frequency response measurement of one of the speakers. Note the
+frequency lines seem to be slightly misaligned, compared to the CSV
+output from the program. I can not hear several of these are high
+frequencies, according to measurement from
+<a href="http://freehearingtestsoftware.com">Free Hearing Test
+Software</a>, an freeware system to measure your hearing (still
+looking for a free software alternative), so I do not know if they are
+coming out out the speakers. I thus do not quite know how to figure
+out if the missing frequencies is a problem with the microphone, the
+amplifier or the speakers, but I managed to rule out the audio card in my
+PC by measuring my Bose noise canceling headset using its own
+microphone. This setup was able to see the high frequency tones, so
+the problem with my stereo had to be in the amplifier or speakers.</p>
+
+<p>Anyway, to try to role out one factor I ended up picking up a new
+set of speakers at a flee marked, and these work a lot better than the
+old speakers, so I guess the microphone and amplifier is OK. If you
+need to measure your own speakers, check out AUDMES. If more people
+get involved, perhaps the project could become good enough to
+<a href="https://bugs.debian.org/910876">include in Debian</a>? And if
+you know of some other free software to measure speakers and amplifier
+performance, please let me know. I am aware of the freeware option
+<a href="https://www.roomeqwizard.com/">REW</a>, but I want something
+that can be developed also when the vendor looses interest.</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>Web browser integration of VLC with Bittorrent support</title>
+ <link>http://people.skolelinux.org/pere/blog/Web_browser_integration_of_VLC_with_Bittorrent_support.html</link>
+ <guid isPermaLink="true">http://people.skolelinux.org/pere/blog/Web_browser_integration_of_VLC_with_Bittorrent_support.html</guid>
+ <pubDate>Sun, 21 Oct 2018 09:50:00 +0200</pubDate>
+ <description><p>Bittorrent is as far as I know, currently the most efficient way to
+distribute content on the Internet. It is used all by all sorts of
+content providers, from national TV stations like
+<a href="https://www.nrk.no/">NRK</a>, Linux distributors like
+<a href="https://www.debian.org/">Debian</a> and
+<a href="https://www.ubuntu.com/">Ubuntu</a>, and of course the
+<a href="https://archive.org/">Internet archive</A>.
+
+<p>Almost a month ago
+<a href="https://tracker.debian.org/pkg/vlc-plugin-bittorrent">a new
+package adding Bittorrent support to VLC</a> became available in
+Debian testing and unstable. To test it, simply install it like
+this:</p>
+
+<p><pre>
+apt install vlc-plugin-bittorrent
+</pre></p>
+
+<p>Since the plugin was made available for the first time in Debian,
+several improvements have been made to it. In version 2.2-4, now
+available in both testing and unstable, a desktop file is provided to
+teach browsers to start VLC when the user click on torrent files or
+magnet links. The last part is thanks to me finally understanding
+what the strange x-scheme-handler style MIME types in desktop files
+are used for. By adding x-scheme-handler/magnet to the MimeType entry
+in the desktop file, at least the browsers Firefox and Chromium will
+suggest to start VLC when selecting a magnet URI on a web page. The
+end result is that now, with the plugin installed in Buster and Sid,
+one can visit any
+<a href="https://archive.org/details/CopyingIsNotTheft1080p">Internet
+Archive page with movies</a> using a web browser and click on the
+torrent link to start streaming the movie.</p>
+
+<p>Note, there is still some misfeatures in the plugin. One is the
+fact that it will hang and
+<a href="https://github.com/johang/vlc-bittorrent/issues/13">block VLC
+from exiting until the torrent streaming starts</a>. Another is the
+fact that it
+<a href="https://github.com/johang/vlc-bittorrent/issues/9">will pick
+and play a random file in a multi file torrent</a>. This is not
+always the video file you want. Combined with the first it can be a
+bit hard to get the video streaming going. But when it work, it seem
+to do a good job.</p>
+
+<p>For the Debian packaging, I would love to find a good way to test
+if the plugin work with VLC using autopkgtest. I tried, but do not
+know enough of the inner workings of VLC to get it working. For now
+the autopkgtest script is only checking if the .so file was
+successfully loaded by VLC. If you have any suggestions, please
+submit a patch to the Debian bug tracking system.</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>Release 0.2 of free software archive system Nikita announced</title>
+ <link>http://people.skolelinux.org/pere/blog/Release_0_2_of_free_software_archive_system_Nikita_announced.html</link>
+ <guid isPermaLink="true">http://people.skolelinux.org/pere/blog/Release_0_2_of_free_software_archive_system_Nikita_announced.html</guid>
+ <pubDate>Thu, 18 Oct 2018 14:40:00 +0200</pubDate>
+ <description><p>This morning, the new release of the
+<a href="https://gitlab.com/OsloMet-ABI/nikita-noark5-core/">Nikita
+Noark 5 core project</a> was
+<a href="https://lists.nuug.no/pipermail/nikita-noark/2018-October/000406.html">announced
+on the project mailing list</a>. The free software solution is an
+implementation of the Norwegian archive standard Noark 5 used by
+government offices in Norway. These were the changes in version 0.2
+since version 0.1.1 (from NEWS.md):
+
+<ul>
+ <li>Fix typos in REL names</li>
+ <li>Tidy up error message reporting</li>
+ <li>Fix issue where we used Integer.valueOf(), not Integer.getInteger()</li>
+ <li>Change some String handling to StringBuffer</li>
+ <li>Fix error reporting</li>
+ <li>Code tidy-up</li>
+ <li>Fix issue using static non-synchronized SimpleDateFormat to avoid
+ race conditions</li>
+ <li>Fix problem where deserialisers were treating integers as strings</li>
+ <li>Update methods to make them null-safe</li>
+ <li>Fix many issues reported by coverity</li>
+ <li>Improve equals(), compareTo() and hash() in domain model</li>
+ <li>Improvements to the domain model for metadata classes</li>
+ <li>Fix CORS issues when downloading document</li>
+ <li>Implementation of case-handling with registryEntry and document upload</li>
+ <li>Better support in Javascript for OPTIONS</li>
+ <li>Adding concept description of mail integration</li>
+ <li>Improve setting of default values for GET on ny-journalpost</li>
+ <li>Better handling of required values during deserialisation </li>
+ <li>Changed tilknyttetDato (M620) from date to dateTime</li>
+ <li>Corrected some opprettetDato (M600) (de)serialisation errors.</li>
+ <li>Improve parse error reporting.</li>
+ <li>Started on OData search and filtering.</li>
+ <li>Added Contributor Covenant Code of Conduct to project.</li>
+ <li>Moved repository and project from Github to Gitlab.</li>
+ <li>Restructured repository, moved code into src/ and web/.</li>
+ <li>Updated code to use Spring Boot version 2.</li>
+ <li>Added support for OAuth2 authentication.</li>
+ <li>Fixed several bugs discovered by Coverity.</li>
+ <li>Corrected handling of date/datetime fields.</li>
+ <li>Improved error reporting when rejecting during deserializatoin.</li>
+ <li>Adjusted default values provided for ny-arkivdel, ny-mappe,
+ ny-saksmappe, ny-journalpost and ny-dokumentbeskrivelse.</li>
+ <li>Several fixes for korrespondansepart*.</li>
+ <li>Updated web GUI:
+ <ul>
+ <li>Now handle both file upload and download.</li>
+ <li>Uses new OAuth2 authentication for login.</li>
+ <li>Forms now fetches default values from API using GET.</li>
+ <li>Added RFC 822 (email), TIFF and JPEG to list of possible file formats.</li>
+ </ul></li>
+</ul>
+
+<p>The changes and improvements are extensive. Running diffstat on
+the changes between git tab 0.1.1 and 0.2 show 1098 files changed,
+108666 insertions(+), 54066 deletions(-).</p>
+
+<p>If free and open standardized archiving API sound interesting to
+you, please contact us on IRC
+(<a href="irc://irc.freenode.net/%23nikita">#nikita on
+irc.freenode.net</a>) or email
+(<a href="https://lists.nuug.no/mailman/listinfo/nikita-noark">nikita-noark
+mailing list</a>).</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>Fetching trusted timestamps using the rfc3161ng python module</title>
+ <link>http://people.skolelinux.org/pere/blog/Fetching_trusted_timestamps_using_the_rfc3161ng_python_module.html</link>
+ <guid isPermaLink="true">http://people.skolelinux.org/pere/blog/Fetching_trusted_timestamps_using_the_rfc3161ng_python_module.html</guid>
+ <pubDate>Mon, 8 Oct 2018 12:30:00 +0200</pubDate>
+ <description><p>I have earlier covered the basics of trusted timestamping using the
+'openssl ts' client. See blog post for
+<a href="http://people.skolelinux.org/pere/blog/Public_Trusted_Timestamping_services_for_everyone.html">2014</a>,
+<a href="http://people.skolelinux.org/pere/blog/syslog_trusted_timestamp___chain_of_trusted_timestamps_for_your_syslog.html">2016</a>
+and
+<a href="http://people.skolelinux.org/pere/blog/Idea_for_storing_trusted_timestamps_in_a_Noark_5_archive.html">2017</a>
+for those stories. But some times I want to integrate the timestamping
+in other code, and recently I needed to integrate it into Python.
+After searching a bit, I found
+<a href="https://dev.entrouvert.org/projects/python-rfc3161">the
+rfc3161 library</a> which seemed like a good fit, but I soon
+discovered it only worked for python version 2, and I needed something
+that work with python version 3. Luckily I next came across
+<a href="https://github.com/trbs/rfc3161ng/">the rfc3161ng library</a>,
+a fork of the original rfc3161 library. Not only is it working with
+python 3, it have fixed a few of the bugs in the original library, and
+it has an active maintainer. I decided to wrap it up and make it
+<a href="https://tracker.debian.org/pkg/python-rfc3161ng">available in
+Debian</a>, and a few days ago it entered Debian unstable and testing.</p>
+
+<p>Using the library is fairly straight forward. The only slightly
+problematic step is to fetch the required certificates to verify the
+timestamp. For some services it is straight forward, while for others
+I have not yet figured out how to do it. Here is a small standalone
+code example based on of the integration tests in the library code:</p>
+
+<pre>
+#!/usr/bin/python3
+
+"""
+
+Python 3 script demonstrating how to use the rfc3161ng module to
+get trusted timestamps.
+
+The license of this code is the same as the license of the rfc3161ng
+library, ie MIT/BSD.
+
+"""
+
+import os
+import pyasn1.codec.der
+import rfc3161ng
+import subprocess
+import tempfile
+import urllib.request
+
+def store(f, data):
+ f.write(data)
+ f.flush()
+ f.seek(0)
+
+def fetch(url, f=None):
+ response = urllib.request.urlopen(url)
+ data = response.read()
+ if f:
+ store(f, data)
+ return data
+
+def main():
+ with tempfile.NamedTemporaryFile() as cert_f,\
+ tempfile.NamedTemporaryFile() as ca_f,\
+ tempfile.NamedTemporaryFile() as msg_f,\
+ tempfile.NamedTemporaryFile() as tsr_f:
+
+ # First fetch certificates used by service
+ certificate_data = fetch('https://freetsa.org/files/tsa.crt', cert_f)
+ ca_data_data = fetch('https://freetsa.org/files/cacert.pem', ca_f)
+
+ # Then timestamp the message
+ timestamper = \
+ rfc3161ng.RemoteTimestamper('http://freetsa.org/tsr',
+ certificate=certificate_data)
+ data = b"Python forever!\n"
+ tsr = timestamper(data=data, return_tsr=True)
+
+ # Finally, convert message and response to something 'openssl ts' can verify
+ store(msg_f, data)
+ store(tsr_f, pyasn1.codec.der.encoder.encode(tsr))
+ args = ["openssl", "ts", "-verify",
+ "-data", msg_f.name,
+ "-in", tsr_f.name,
+ "-CAfile", ca_f.name,
+ "-untrusted", cert_f.name]
+ subprocess.check_call(args)
+
+if '__main__' == __name__:
+ main()
+</pre>
+
+<p>The code fetches the required certificates, store them as temporary
+files, timestamp a simple message, store the message and timestamp to
+disk and ask 'openssl ts' to verify the timestamp. A timestamp is
+around 1.5 kiB in size, and should be fairly easy to store for future
+use.</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>Automatic Google Drive sync using grive in Debian</title>
<link>http://people.skolelinux.org/pere/blog/Automatic_Google_Drive_sync_using_grive_in_Debian.html</link>
</description>
</item>
- <item>
- <title>A bit more on privacy respecting health monitor / fitness tracker</title>
- <link>http://people.skolelinux.org/pere/blog/A_bit_more_on_privacy_respecting_health_monitor___fitness_tracker.html</link>
- <guid isPermaLink="true">http://people.skolelinux.org/pere/blog/A_bit_more_on_privacy_respecting_health_monitor___fitness_tracker.html</guid>
- <pubDate>Mon, 13 Aug 2018 09:00:00 +0200</pubDate>
- <description><p>A few days ago, I wondered if there are any privacy respecting
-health monitors and/or fitness trackers available for sale these days.
-I would like to buy one, but do not want to share my personal data
-with strangers, nor be forced to have a mobile phone to get data out
-of the unit. I've received some ideas, and would like to share them
-with you.
-
-One interesting data point was a pointer to a Free Software app for
-Android named
-<a href="https://github.com/Freeyourgadget/Gadgetbridge/">Gadgetbridge</a>.
-It provide cloudless collection and storing of data from a variety of
-trackers. Its
-<a href="https://github.com/Freeyourgadget/Gadgetbridge/#supported-devices">list
-of supported devices</a> is a good indicator for units where the
-protocol is fairly open, as it is obviously being handled by Free
-Software. Other units are reportedly encrypting the collected
-information with their own public key, making sure only the vendor
-cloud service is able to extract data from the unit. The people
-contacting me about Gadgetbirde said they were using
-<a href="https://us.amazfit.com/shop/bip?variant=336750">Amazfit
-Bip</a> and
-<a href="http://www.xiaomimi6phone.com/xiaomi-mi-band-3-features-release-date-rumors/">Xiaomi
-Band 3</a>.</p>
-
-<p>I also got a suggestion to look at some of the units from Garmin.
-I was told their GPS watches can be connected via USB and show up as a
-USB storage device with
-<a href="https://www.gpsbabel.org/htmldoc-development/fmt_garmin_fit.html">Garmin
-FIT files</a> containing the collected measurements. While
-proprietary, FIT files apparently can be read at least by
-<a href="https://www.gpsbabel.org">GPSBabel</a> and the
-<a href="https://apps.nextcloud.com/apps/gpxpod">GpxPod</a> Nextcloud
-app. It is unclear to me if they can read step count and heart rate
-data. The person I talked to was using a
-<a href="https://buy.garmin.com/en-US/US/p/564291">Garmin Forerunner
-935</a>, which is a fairly expensive unit. I doubt it is worth it for
-a unit where the vendor clearly is trying its best to move from open
-to closed systems. I still remember when Garmin dropped NMEA support
-in its GPSes.</p>
-
-<p>A final idea was to build ones own unit, perhaps by basing it on a
-wearable hardware platforms like
-<a href="https://learn.adafruit.com/flora-geo-watch">the Flora Geo
-Watch</a>. Sound like fun, but I had more money than time to spend on
-the topic, so I suspect it will have to wait for another time.</p>
-
-<p>While I was working on tracking down links, I came across an
-inspiring TED talk by Dave Debronkart about
-<a href="https://archive.org/details/DavedeBronkart_2010X">being a
-e-patient</a>, and discovered the web site
-<a href="https://participatorymedicine.org/epatients/">Participatory
-Medicine</a>. If you too want to track your own health and fitness
-without having information about your private life floating around on
-computers owned by others, I recommend checking it out.</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>Privacy respecting health monitor / fitness tracker?</title>
- <link>http://people.skolelinux.org/pere/blog/Privacy_respecting_health_monitor___fitness_tracker_.html</link>
- <guid isPermaLink="true">http://people.skolelinux.org/pere/blog/Privacy_respecting_health_monitor___fitness_tracker_.html</guid>
- <pubDate>Tue, 7 Aug 2018 16:00:00 +0200</pubDate>
- <description><p>Dear lazyweb,</p>
-
-<p>I wonder, is there a fitness tracker / health monitor available for
-sale today that respect the users privacy? With this I mean a
-watch/bracelet capable of measuring pulse rate and other
-fitness/health related values (and by all means, also the correct time
-and location if possible), which is <strong>only</strong> provided for
-me to extract/read from the unit with computer without a radio beacon
-and Internet connection. In other words, it do not depend on a cell
-phone app, and do make the measurements available via other peoples
-computer (aka "the cloud"). The collected data should be available
-using only free software. I'm not interested in depending on some
-non-free software that will leave me high and dry some time in the
-future. I've been unable to find any such unit. I would like to buy
-it. The ones I have seen for sale here in Norway are proud to report
-that they share my health data with strangers (aka "cloud enabled").
-Is there an alternative? I'm not interested in giving money to people
-requiring me to accept "privacy terms" to allow myself to measure my
-own health.</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>Sharing images with friends and family using RSS and EXIF/XMP metadata</title>
- <link>http://people.skolelinux.org/pere/blog/Sharing_images_with_friends_and_family_using_RSS_and_EXIF_XMP_metadata.html</link>
- <guid isPermaLink="true">http://people.skolelinux.org/pere/blog/Sharing_images_with_friends_and_family_using_RSS_and_EXIF_XMP_metadata.html</guid>
- <pubDate>Tue, 31 Jul 2018 23:30:00 +0200</pubDate>
- <description><p>For a while now, I have looked for a sensible way to share images
-with my family using a self hosted solution, as it is unacceptable to
-place images from my personal life under the control of strangers
-working for data hoarders like Google or Dropbox. The last few days I
-have drafted an approach that might work out, and I would like to
-share it with you. I would like to publish images on a server under
-my control, and point some Internet connected display units using some
-free and open standard to the images I published. As my primary
-language is not limited to ASCII, I need to store metadata using
-UTF-8. Many years ago, I hoped to find a digital photo frame capable
-of reading a RSS feed with image references (aka using the
-&lt;enclosure&gt; RSS tag), but was unable to find a current supplier
-of such frames. In the end I gave up that approach.</p>
-
-<p>Some months ago, I discovered that
-<a href="https://www.jwz.org/xscreensaver/">XScreensaver</a> is able to
-read images from a RSS feed, and used it to set up a screen saver on
-my home info screen, showing images from the Daily images feed from
-NASA. This proved to work well. More recently I discovered that
-<a href="https://kodi.tv">Kodi</a> (both using
-<a href="https://www.openelec.tv/">OpenELEC</a> and
-<a href="https://libreelec.tv">LibreELEC</a>) provide the
-<a href="https://github.com/grinsted/script.screensaver.feedreader">Feedreader</a>
-screen saver capable of reading a RSS feed with images and news. For
-fun, I used it this summer to test Kodi on my parents TV by hooking up
-a Raspberry PI unit with LibreELEC, and wanted to provide them with a
-screen saver showing selected pictures from my selection.</p>
-
-<p>Armed with motivation and a test photo frame, I set out to generate
-a RSS feed for the Kodi instance. I adjusted my <a
-href="https://freedombox.org/">Freedombox</a> instance, created
-/var/www/html/privatepictures/, wrote a small Perl script to extract
-title and description metadata from the photo files and generate the
-RSS file. I ended up using Perl instead of python, as the
-libimage-exiftool-perl Debian package seemed to handle the EXIF/XMP
-tags I ended up using, while python3-exif did not. The relevant EXIF
-tags only support ASCII, so I had to find better alternatives. XMP
-seem to have the support I need.</p>
-
-<p>I am a bit unsure which EXIF/XMP tags to use, as I would like to
-use tags that can be easily added/updated using normal free software
-photo managing software. I ended up using the tags set using this
-exiftool command, as these tags can also be set using digiKam:</p>
-
-<blockquote><pre>
-exiftool -headline='The RSS image title' \
- -description='The RSS image description.' \
- -subject+=for-family photo.jpeg
-</pre></blockquote>
-
-<p>I initially tried the "-title" and "keyword" tags, but they were
-invisible in digiKam, so I changed to "-headline" and "-subject". I
-use the keyword/subject 'for-family' to flag that the photo should be
-shared with my family. Images with this keyword set are located and
-copied into my Freedombox for the RSS generating script to find.</p>
-
-<p>Are there better ways to do this? Get in touch if you have better
-suggestions.</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>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>
-
</channel>
</rss>
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