Tag Archives: motion capture

Musikkteknologidagene 2012

Alexander holding a keynote lecture at Musikkteknologidagene 2012 (Photo: Nathan Wolek).

Last week I held a keynote lecture at the Norwegian music technology conference Musikkteknologidagene, by (and at) the Norwegian Academy of Music and NOTAM. The talk was titled: “Embodying the human body in music technology”, and was an attempt at explaining why I believe we need to put more emphasis on human-friendly technologies, and why the field of music cognition is very much connected to that of music technology. I got a comment that it would have been better to exchange “embodying” with “embedding” in my title, and I totally agree. So now I already have a title for my next talk!

Sverm demo
One of the “pieces” we did for the Sverm demo at Musikkteknologidagene 2012: three performers standing still and controlling a sine tone each based on their micromovements.

Besides my talk, we also did a small performance of parts of the Sverm project that I am working on together with an interdisciplinary group of sound, movement and light artists. We showed three parts: (1) very slow movement with changing lights (2) sonification of the micromovements of people standing still (3) micromovement interaction with granular synthesis. This showcase was based on the work we have done since the last performance and seminar.

Besides the things I was involved in myself during Musikkteknologidagene, I was very happy about being “back” at the conference after a couple of years of “absence” (I had enough with organising NIME last year). It is great to find that the conference is still alive and manages to gather people doing interesting stuff in and with music technology in Norway.

Sverm talking
Alexander talking about the Sverm project and fourMs motion capture lab at Musikkteknologidagene 2012 (Photo: Nathan Wolek).

When I started up the conference series back in 2005, the idea was to create a meeting place for music technology people in Norway. Fortunately, NOTAM has taken on the responsibility of finding and supporting local organisers that can host it every year. So far it has been bouncing back and forth between Oslo, Trondheim and Bergen, and I think it is now time that it moves on to Kristiansand, Tromsø and Stavanger. All these cities now have small active music technology communities, and some very interesting festivals (Punkt, Insomnia, Numusic) that it could be connected to.

As expected, the number of people attending the conference has been going up and down over the years. In general I find that it is always difficult to get people from Oslo to attend, something that I find slightly embarassing, but which can probably be explained by the overwhelming amount of interesting things happening in this comparably little capital at any point in time.

We had the first snow this year during Musikkteknologidagene, a good time to stay indoors at NOTAM listening to presentations.

The first years of Musikkteknologidagene we mainly spent on informing each other of what we are all doing, really just getting to know each other. Over the years the focus has been shifted more towards “real” presentations, and all the presentations I heard this year were very interesting and inspiring. This is a good sign that the field of music technology has matured in Norway. Several institutions have been able to start up research and educational programs in fields somehow related to music technology, and I think we are about to reach a critical mass of groups of people involved in the field, not only a bunch of individual researchers and artists trying to survive. This year we agreed that we are now going to make a communal effort of building up a database of all institutions and individuals involved in the field, and develop a roadmap along the lines of what was made in the S2S2 project.

All in all, this year’s Musikkteknologidagene was a fun experience, and I am already looking forwards to next year’s edition.

Paper #2 at SMC 2012: Noise level in IR mocap systems

Yesterday I presented a paper on motiongrams at the Sound and Music Computing conference in Copenhagen. Today I will present the paper A study of the noise-level in two infrared marker-based motion capture systems. This is a quite nerdy, in-depth study of the noise-level of two of our motion capture systems.


With musical applications in mind, this paper reports on the level of noise observed in two commercial infrared marker-based motion capture systems: one high-end (Qualisys) and one affordable (OptiTrack). We have tested how various features (calibration volume, marker size, sampling frequency, etc.) influence the noise level of markers lying still, and fixed to subjects standing still. The conclusion is that the motion observed in humans standing still is usually considerably higher than the noise level of the systems. Dependent on the system and its calibration, however, the signal-to-noise-ratio may in some cases be problematic.


  • Full paper [PDF]
  • Poster [PDF]


Jensenius, A. R., Nymoen, K., Skogstad, S. A., and Voldsund, A. (2012). A study of the noise-level in two infrared marker-based motion capture systems. In Proceedings of the 9th Sound and Music Computing Conference, pages 258–263, Copenhagen.


   Address = {Copenhagen},
   Author = {Jensenius, Alexander Refsum and Nymoen, Kristian and Skogstad, St{\aa}le A. and Voldsund, Arve},
   Booktitle = {Proceedings of the 9th Sound and Music Computing Conference},
   Pages = {258--263},
   Title = {A Study of the Noise-Level in Two Infrared Marker-Based Motion Capture Systems},
   Year = {2012}}


Yesterday Miles Phillips suggested that the word “motionlessness” may be what I am after when it comes to describing the act of standing still. He further pointed me to a web site with a list of the world records for motionlessness. The rules to compete in motionlessness is as follows:

  1. The record is for continuously standing motionless.
  2. You must stand: sitting is not allowed.
  3. No facial movements are allowed other then the involuntary blinking of the eye.
  4. Deep breathing is permitted provided it does not involve observable movement notably greater than that in normal breathing.
  5. No rest breaks are allowed at any point during the event.
  6. The venue for such an event should be such that the general public can view.

But from my point of view, being interested in micromovements, I would be very curious to see how still these record holders actually were.

At the ArtsIT conference next month I will present the results of a study on standstill that I have conducted together with Kari Anne Bjerkestrand. I have given a sneak peek of the data earlier, and below is another figure with plots of motion capture data from the study. The plots show data of a marker placed on the neck, from six different 10-minute long standstill recordings of myself and Kari Anne. It is only the vertical position of the marker that is plotted.

Arj c7 selected5

From the plots we can see that the running marker displacement was at the scale of only a few millimeters, with a maximum displacement of less than 10mm. It can be argued that this is not much, but it certainly is not absolutely still.

One thing is the quantitative data, another is our subjective experience of standing still. Even though we tried our best to stand physically still, we could easily notice how we were swaying back and forth, doing postural adjustments, etc. Observing the video recordings of ourselves afterwards, it is also possible to see these micromovements through visual inspection only.

Based on these findings, I would be very curious to see how still a person can actually stand, not only measured in hours and minutes, but also in millimeters. So to any aspiring world record breakers: please come and do your next attempt in our lab!

Open lab

We have slowly been moving into our new lab spaces over the last weeks. The official opening of the labs is scheduled for Friday 26 September, but we had a pre-opening “Open lab” for the new music students last week, and here are some of the pictures research coordinator Anne Cathrine Wesnes shot during the presentation.

Here I am telling the students a little about our new research group, and showing the main room:

Showing some realtime video analysis tools, including motion history images and motiongrams:
Video analysis
Demonstrating our new Optitrack motion capture system:
Motion capture
Kristian Nymoen showing the “self-playing piano”, a Disklavier controlled by the movements of two Polhemus electromagnetic trackers.