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Archive for July 2011

Getting the Lion to RoR


I’m in the process of upgrading to OSX 10.7 Lion. The install process went smooth, and I’m now testing and updating the many programs I have installed and use. Most of them seem to be fine.

OSX no longer comes with Ruby On Rails (RoR) preinstalled. That makes sense to me. The preinstalled versions of Rails always lagged behind, and the first one had to do was to update it all.

As expected, no Rails showed up initially after the upgrade. But having installed the latest version:

sudo gen install rails

all previous versions and gems remains available, as can be seen by running:

gem list

I also had to reinstall ImageMagick, used by various Rails applications for image rescaling, cropping, etc. Following the migration instructions at MacPorts I cleaned out all previously installed ports, and then reinstalled ImageMagick. That seemed to go smooth.

I have tested the various Rails applications that I am developing or testing locally, and the only problem I have observed is that Webrick, the default web server used for serving Development versions of the apps, struggles to deliver the content of the Public folder. I often got the following message, while images and CSS fail to show up:

rails ERROR NoMethodError: private method 'gsub!'

The workaround, according to this thread seems to be to install mongrel, and use mongrel as Development server rather than Webrick, with the command:

ruby script/server mongrel

The only thing left to test is Passenger for Deployment.

Screen capture of single window



I just discovered a new way of doing a screen capture of a single window on Mac OSX: After pressing CMD+SHIFT+4, hit the space bar.

Story of Isaac


The door it opened slowly,
My father he came in,
I was nine years old.
And he stood so tall above me,
His blue eyes they were shining
And his voice was very cold.
He said, “I’ve had a vision
And you know I’m strong and holy,
I must do what I’ve been told.”
So he started up the mountain,
I was running, he was walking,
And his axe was made of gold.

Well, the trees they got much smaller,
The lake a lady’s mirror,
We stopped to drink some wine.
Then he threw the bottle over.
Broke a minute later
And he put his hand on mine.
Thought I saw an eagle
But it might have been a vulture,
I never could decide.
Then my father built an altar,
He looked once behind his shoulder,
He knew I would not hide.

You who build these altars now
To sacrifice these children,
You must not do it anymore.
A scheme is not a vision
And you never have been tempted
By a demon or a god.
You who stand above them now,
Your hatchets blunt and bloody,
You were not there before,
When I lay upon a mountain
And my father’s hand was trembling
With the beauty of the world.

And if you call me brother now,
Forgive me if I inquire,
“Just according to whose plan?”
When it all comes down to dust
I will kill you if I must,
I will help you if I can.
When it all comes down to dust
I will help you if I must,
I will kill you if I can.
And mercy on our uniform,
Man of peace or man of war,
The peacock spreads his fan.

Leonard Cohen

Jostein Gundersen on his artistic research fellowship


Interview with Jostein Gundersen (in Norwegian) in 2009 when he concluded his research fellowship in the arts. The interview took place at Håkonshallen.

Josten is now teaching at the Grieg Academy, and is the artistic director of the early music ensemble Currentes.

Shoot and run using MIDI



Screenshot from the game as art (or art as game)
Jeff Koon must die!!! by Hunter Jonakin

I just learned from Nils Peters that the MIDI specification was extended in 2009 with a set of descriptors for Three Dimensional Sound Controllers. According to MMA “the advancement of the MIDI standard from simple stereo rendering to true three-dimensional sound rendering becomes the next logical step in MIDI evolution.”

The specification is motivated from use in gaming and virtual reality, and settles for using a spherical coordinate system rather than Cartesian, using “azimuth angle, elevation angle, and distance to describe the object, much like firing artillery.” I have never though of spherical coordinates in terms of “shoot and run” metaphores before, but then again I am a pasifist, so what is to be expected?



Parameters for distance attenuation in the MIDI specification.

The MIDI specification uses 14bit RPN (Registered Parameter Numbers) for parameters. There are several interesting points in the specification, including:

  • A navigational coordinate system is used. 0° is in front, +90° to the right and -90° to the left. 14 bit resolution azimuth is described wih a step size of 0.02°.
  • Elevation is full circle (-180° to 180°) rather than -90° to 90°.
  • Distance is defined as a ration to the maximum distance permitted: The distance ration parameter controls the ratio of the current distance that an object is away from the listener to the maximum distance. There are additional parameters for setting maximum distance, gain at maximum distance, and a reference distance ratio. The relationship between these parameters is illustrated above.

The specification also propose default equations for distance attenuation, and a second alternative attenuation scheme “found in the litterature”. This second scheme is the same that we use for distance attenuation in DBAP (Distance-based amplitude panning).


Also of interest at the MMA web site is a white paper from 2008 comparing MIDI and OSC.

Surround recordings as artistic material



Last fall BEK purchased a SoundField microphone. For me the ability to capture spatial information has led to a renewed interest in doing sound and field recordings. I have spent quite a bit of time investigating the work flow required for recording, encoding and decoding, as well as how the recordings might be used artistically in ways that I find meaningful.

Recently AudioFinder was updated to support display and playback of multichannel sound files. For me that helps a lot towards using AudioFinder as an audio assets application.

Also, this spring Harpex was released. Harpex is a parametric decoder of ambisonic signals, and I first heard of it from Natasha Barrett. I am really impressed with the decoding abilities of Harpex, it is producing way better spatial definition than the software decoding plugin that comes with the SoundField microphone itself. For real-time generative sound installations Harpex is pretty CPU-intensive, and I am not sure how well it will work to use it live, but for pre-processing of sound, it’s really good.

In addition, Harpex used as a plugin with AudioFinder helps me auditing spatial sound over headphones, which is useful when away from the studio.


In the last few weeks I have also worked on extending Distance-Based Amplitude Panning (DBAP) to support ambisonic sources. DBAP was first developed for the Living Room workshop/installation in Trondheim in 2003, and presented at ICMC 2009:

Most common techniques for spatialization require the listener to be positioned at a “sweet spot” surrounded by loudspeakers. For practical concert, stage, and installation applications such layouts may not be desirable. Distance-based amplitude panning (DBAP) offers an alternative panning-based spatialization method where no assumptions are made concerning the layout of the speaker array nor the position of the listener.

So far DBAP has been used for spatialisation of mono sources.

But my recent work on surround recordings, as well as a demonstration of research on source directivity at the SpatDIF meeting at IRCAM a year ago got me thinking about the possibility of using B-format signals as input to DBAP.

My hope is that this might produce sounding results with a spatial distribution and differentiation that goes beyond panning of mono sources, while also offering possibilities of a sculptural choreographing of sound that might be difficult to achieve through decoding alone.

DBAP with B-format sources have been developed as a Max external that eventually will make it into Jamoma, and a Jamoma module to go along with it.

I have tested it out at my studios with seven speakers positioned the similarly to the help patch screenshot above, and the initial tests are promising. The effect, as compared to mono DBAP, is subtle, but gets closer towards crating scenographic illusions through sound alone.

Today I’ll be doing a large scale test at Håkonshallen.


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