X-Git-Url: https://pere.pagekite.me/gitweb/homepage.git/blobdiff_plain/48242bda221d48f034db275c4758ac81cc92d31b..7e36d7f1ee3064b18e93a22e424476eb8b4e0b64:/blog/index.html?ds=inline diff --git a/blog/index.html b/blog/index.html index 95d6887c41..cb89379d47 100644 --- a/blog/index.html +++ b/blog/index.html @@ -19,6 +19,235 @@ +
+
Measuring the speaker frequency response using the AUDMES free software GUI - nice free software
+
22nd October 2018
+

+ +

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 +Speaker +Testing and Analysis describing how to test speakers, and it listing +several software options, among them +AUDio MEasurement +System (AUDMES). 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 +Understanding +Speaker Specifications and Frequency Response and an article from +ecoustics on +Understanding +Speaker Frequency Response, 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.

+ +

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.

+ +

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 +Free Hearing Test +Software, 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.

+ +

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 include +in Debian? 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 REW, +but I want something that can be developed also when the vendor +looses interest.

+ +

As usual, if you use Bitcoin and want to show your support of my +activities, please send Bitcoin donations to my address +15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b.

+
+
+ + + Tags: english, nice free software. + + +
+
+
+ +
+
Web browser integration of VLC with Bittorrent support
+
21st October 2018
+

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 +NRK, Linux distributors like +Debian and +Ubuntu, and of course the +Internet archive. + +

Almost a month ago +a new +package adding Bittorrent support to VLC became available in +Debian testing and unstable. To test it, simply install it like +this:

+ +

+apt install vlc-plugin-bittorrent
+

+ +

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 +Internet +Archive page with movies using a web browser and click on the +torrent link to start streaming the movie.

+ +

Note, there is still some misfeatures in the plugin. One is the +fact that it will hang and +block VLC +from exiting until the torrent streaming starts. Another is the +fact that it +will pick +and play a random file in a multi file torrent. 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.

+ +

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.

+ +

As usual, if you use Bitcoin and want to show your support of my +activities, please send Bitcoin donations to my address +15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b.

+
+
+ + + Tags: english, verkidetfri, video. + + +
+
+
+ +
+
Release 0.2 of free software archive system Nikita announced
+
18th October 2018
+

This morning, the new release of the +Nikita +Noark 5 core project was +announced +on the project mailing list. 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): + +

+ +

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(-).

+ +

If free and open standardized archiving API sound interesting to +you, please contact us on IRC +(#nikita on +irc.freenode.net) or email +(nikita-noark +mailing list).

+ +

As usual, if you use Bitcoin and want to show your support of my +activities, please send Bitcoin donations to my address +15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b.

+
+
+ + + Tags: english, nuug, offentlig innsyn, standard. + + +
+
+
+
Fetching trusted timestamps using the rfc3161ng python module
8th October 2018
@@ -538,225 +767,6 @@ activities, please send Bitcoin donations to my address
-
-
Privacy respecting health monitor / fitness tracker?
-
7th August 2018
-

Dear lazyweb,

- -

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 only 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.

- -

As usual, if you use Bitcoin and want to show your support of my -activities, please send Bitcoin donations to my address -15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b.

-
-
- - - Tags: english. - - -
-
-
- -
-
Sharing images with friends and family using RSS and EXIF/XMP metadata
-
31st July 2018
-

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 -<enclosure> RSS tag), but was unable to find a current supplier -of such frames. In the end I gave up that approach.

- -

Some months ago, I discovered that -XScreensaver 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 -Kodi (both using -OpenELEC and -LibreELEC) provide the -Feedreader -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.

- -

Armed with motivation and a test photo frame, I set out to generate -a RSS feed for the Kodi instance. I adjusted my Freedombox 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.

- -

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:

- -
-exiftool -headline='The RSS image title' \
-  -description='The RSS image description.' \
-  -subject+=for-family photo.jpeg
-
- -

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.

- -

Are there better ways to do this? Get in touch if you have better -suggestions.

- -

As usual, if you use Bitcoin and want to show your support of my -activities, please send Bitcoin donations to my address -15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b.

-
-
- - - Tags: debian, english. - - -
-
-
- -
-
Simple streaming the Linux desktop to Kodi using GStreamer and RTP
-
12th July 2018
-

Last night, I wrote -a -recipe to stream a Linux desktop using VLC to a instance of Kodi. -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.

- -

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 -the JSON-RPC API in -Kodi 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.

- -
-#!/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"
-
- -

I hope you find the approach useful. I know I do.

- -

As usual, if you use Bitcoin and want to show your support of my -activities, please send Bitcoin donations to my address -15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b.

-
-
- - - Tags: debian, english, kodi, video. - - -
-
-
-

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