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provisioning Azure vm’s in bulk using Terraform

For a demo I put together this script, it will provision a group of vm’s in an existing azure vnet. I thought this might be a 5-minute job, but it took me quite a while.

moving ip addresses to another device without downtime: scenarios

For the impatient: arpsend !

We all know the problem: you replace a firewall with another model, correctly configure everything and lose connectivity.

After a few hours, things automagically start working again. Read more »

Ubuntu Linux under vmware: network interfaces

I’m quite busy with VMware these days. I actually believe VMware’s dogma “the virtual machine is more robust and qualitatively better than the physical machine” is correct.

However, after installing two VM’s running Ubuntu Linux to do some failover testing, I noticed something odd about the numbering of the network interfaces. Good old eth0 was missing. Instead, there was an eth1 present…

Now I had this issue in the past, but always worked around it by just using eth1 instead of eth0. But maybe it would be better to find out about this and fix it “the right way”.

The problem is caused by the copying of the virtual machines. I have a VM template which I use as a base image. I then copy and customise this image when I need to implement new VM’s. The process goes like this: Read more »

Cover art resizing

One of the more heated debates involving audio tags is: do you organize your files using one directory for every album and put the cover art into a single file into that album (‘folder.jpg’) or do you embed the cover art into the tags of each and every file? Myself, I embed it into all files.

  • the cover art is always with the file, no matter where I copy it to
  • I do not have to put every album into one folder
  • what about single files? You have to embed the art then since creating a folder for one single file seems…strange.

Read more »

Digital audio players: iTunes

ITunes

Note: this article was originally posted on April 11th, 2007. Some of the mentioned extensions are no longer compatible with later iTunes versions.

Why?

ITunes is Apple’s audio player with versions for both Mac and PC. You can say a lot of things about it:

  • It always seems to ‘know better’
  • It is limited in supported playback formats
  • It feels a bit slow

Yet, : Read more »

MP3 compression settings

A lot of misconceptions exist about audio compression. Bear in mind that the whole idea behind it is to store digital audio but not have it take up too much space on your hard drive. Uncompressed audio is in wav format. You can compress it in 2 ways:

  • Lossless compression: no information is lost, compression is about 50%.
  • Lossy compression: the codec used tries to determine parts of the file you won’t be able to hear anyway and throws them away. The rest is compressed. Compression is determined by either the bitrate you want to give or the quality you want to give. Compression depends upon the bitrate used but can typically be around 80% while staying transparant.

So, no codec (mp3, ogg, aac, …) can ever be said to provide better or worse sound quality. What can be said is that different codecs need a different bitrate (and so, file size) to reach the same quality.

We’ll be compressing lossy. mp3 is an old codec and in theory newer ones such as aac should need a lower bitrate to get the same quality. However…When using the lame mp3 encoder you have an encoder which has excellent tuning. The advantage of using mp3 is that it’s universally supported on all devices. (indeed, most people think about mp3’s when talking about digital audio.) Also note that a song encoded with the same bitrate but by different encoders may have a very diffent quality for different encodings. When encoding to mp3 and if quality is the goal (instead of speed) always use lame! So, MP3 is what we’ll be using here… Read more »

Tagging audio files

There are a few ways I can think of for an audio player to show you all relevant information (artist, title, release year, …) about an audio file.

  • derive it on-the-fly from the filename.
    • disadvantages:
      • only a limited amount of fields can be entered before file names become too long
      • changing a field would require you to rename the file, which will make programs no longer find the file.
      • you need to take care when naming your files, changing your filename format afterwards may be difficult.
    • advantages:
      • ummmm…not sure…
  • derive it from metadata added to the file.
    • disadvantages:
      • a lot of fields are standardized, but some are not. (album artist anyone?)
      • file becomes (only slightly) bigger
    • advantages:
      • very flexible: you can add fields whenever you want

Read more »

The old Leminator Linux section

I originally wrote this website with the idea of posting some information about 2 topics: Linux and old computer emulation (this was back around 1998).

You can find the content of the old site here (though I fear the information is not that relevant anymore). Only the Linux-related information is left.