Martin Gasser

Detecting harmonic change in musical audio

We propose a novel method for detecting changes in the harmonic content of musical audio signals. Our method uses a new model for Equal Tempered Pitch Class Space. This model maps 12-bin chroma vectors to the interior space of a 6-D polytope; pitch classes are mapped onto the vertices of this polytope. Close harmonic relations such as fifths and thirds appear as small Euclidian distances. We calculate the Euclidian distance between analysis frames n +1 and n -1 to develop a harmonic change measure for frame n. A peak in the detection function denotes a transition from one harmonically stable region to another. Initial experiments show that the algorithm can successfully detect harmonic changes such as chord boundaries in polyphonic audio recordings.

Case study: visual analysis of complex, time-dependent simulation results of a diesel exhaust system

In previous work we have presented visualization techniques that provide engineers with a high degree of interactivity and flexibility for analyzing large, time-dependent, and high-dimensional data sets resulting from CFD (computational fluid dynamics) simulations. In this case study we apply our techniques in the fields of the automotive engineering industry and demonstrate how users benefit from using them during their routine analysis, as well as for exploring new phenomena. For coping with some of the special requirements in this application, we adapted and extended parts of the system. A comparison of two related cases of a diesel exhaust system is presented, and some important questions about these cases are addressed.

Limitations of interactive music recommendation based on audio content

We present a study on the limitations of an interactive music recommendation service based on automatic computation of audio similarity. Songs which are, according to the audio similarity function, similar to very many other songs and hence appear unwantedly often in recommendation lists keep a significant proportion of the audio collection from being recommended at all. This problem is studied in-depth with a series of computer experiments including analysis of alternative audio similarity functions and comparison with actual download data.

Interactive Focus+Context Analysis of Large, Time-Dependent Flow Simulation Data

The visualization of time-dependent simulation data, such as data sets from computational fluid dynamics (CFD) simulation, is still a very challenging task. In this paper, we present a new approach for the interactive visual analysis of flow simulation data, which is especially targeted at the analysis of time-dependent data. This supports the flexible specification and visualization of flow features in an interactive setup of multiple linked views. Special emphasis is put on new mechanisms to capture time-dependent features (i.e. flow features that are inherently dependent on time). We propose the integration of attribute derivation into the process of interactive visual analysis to enable the subsequent user access to otherwise implicit properties of the unsteady data in our interactive feature specification framework. All views of this flow analysis setup are linked, in the sense that the features in focus are consistently emphasized in the visualization (more colorful, less transparent) whereas the rest of the data are only shown as context in reduced style. In addition to introducing our new approach, we also demonstrate its use in the context of several application examples.