X-Git-Url: http://pere.pagekite.me/gitweb/homepage.git/blobdiff_plain/a5f4bdf4e8b5407e0e69b78fc77db623de7d967c..5ee2584c6469e6d4e3dd98b13ff5ef44fa65ad0b:/blog/archive/2018/10/index.html diff --git a/blog/archive/2018/10/index.html b/blog/archive/2018/10/index.html index e9d9c4549b..ca588807c3 100644 --- a/blog/archive/2018/10/index.html +++ b/blog/archive/2018/10/index.html @@ -21,6 +21,371 @@

Entries from October 2018.

+
+
+ 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, noark5, nuug, offentlig innsyn, standard. + + +
+
+
+ +
+
+ Fetching trusted timestamps using the rfc3161ng python module +
+
+ 8th October 2018 +
+
+

I have earlier covered the basics of trusted timestamping using the +'openssl ts' client. See blog post for +2014, +2016 +and +2017 +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 +the +rfc3161 library 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 +the rfc3161ng library, +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 +available in +Debian, and a few days ago it entered Debian unstable and testing.

+ +

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:

+ +
+#!/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()
+
+ +

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.

+ +

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, noark5, sikkerhet. + + +
+
+
+
Automatic Google Drive sync using grive in Debian @@ -104,6 +469,38 @@ activities, please send Bitcoin donations to my address

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