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Page 1 ï~~TOWARDS AN INTERCHANGE FORMAT FOR SPATIAL AUDIO SCENES Gary Kendall Northwestern University Evanston, US soon SARC, Belfast Nils Peters McGill University, CIRMMT Montreal, Canada Matthias Geier Deutsche Telekom Laboratories Berlin, Germany ABSTRACT This extended abstract outlines a proposal for an ICMC panel discussion with the intention to set on the development of a file format to create, store and share spatial audio scenes across 2D/3D audio applications and concert venues. This discussion shall include composers, sonic artists, researchers and developers in order to make such a format widely acceptable. Keywords: Panel Discussion, 3D Audio, Spatial Music, Scene Description, Spatial Perception, Standardization, Portability 1. INITIAL PROBLEM Several spatialization algorithms and many software implementations exist to create spatialized soundfields. We found that many spatialization algorithms use a selfcontained syntax and storage-format, wherein sequences of control messages (e.g. trajectories to move a sound in space) programmed for one application are incompatible with any other implementation. Furthermore, as shown in Figure 1, more and more concert halls and research facilities are equipped with a large number of loudspeakers. Although these venues might provide a good environment for 3D audio applications, they often differ in terms of room size, their technical specifications and the applied audio rendering concept. The lack of a common format for controlling spatialization across different rendering platforms and venues complicates the portability of compositions and requires manual synchronization and conversion of control data - a time consuming affair. Incompatible data formats also prevent collaboration between researchers and institutions. Therefore we call for the collaborative development of a format to describe spatial audio information in a structured way to support real-time and non-real-time applications. 2. EXISTING SCENE DESCRIPTION FORMATS Over the years several formats and frameworks were developed with the intention to allow for platformindependent playback and re-usability of scene elements, as there were among others: * MPEG-4 Advanced AudioBIFF,  * OpenAL,  * X3D, 1 * XML3DAUDIO,  * Audio3D,  * SSP,  However, no format has established itself in the spatial audio community because these formats are primary tailored to multimedia and gaming applications and do not necessarily consider the special requirements of spatial music performances in concert venues. Furthermore it is the authors opinion that artists were not sufficiently involved in the development of these formats. Efforts have been made recently towards the outlined problem e.g. in  and , but discussion with the community is needed to cover all needs and to create a common format which everyone is willing to use. 3. HIGH-LEVEL SPATIAL DESCRIPTORS In addition to low level information, high-level spatial descriptors are necessary in order to create a meaningful and interchangeable scene description. The authors of  and  created a vocabulary of spatial-perceptual attributes for describing the organization of reproduced sound sources. 4. ICMC PANEL DISCUSSION 4.1. Purpose The ICMC is the oldest conference for computer music - an event with reputation where developers, musicians and composers exchange ideas. Through our research, we know that there are different groups, working on such format to describe audio scenes. To develop a well accepted format, we want to bring these groups together to share and enhance their ideas with the community. 4.2. Potential discussion-topics * The challenge of porting spatial music from a studio into concert venues * Hardware specifications * Scaling of scenes 1http://www.web3d.org/x3d/
Page 2 ï~~* Organization and handling of sources groups m K Necessary source parameters Av....ta f Requirements for deterministic/interactive scenes s Differences between 2D and 3D scene description * Authoring and storage in the sameformat? * Integration into existing systems.loth3D * Synchronization to controllers and video devices 05. References  M. Geier, J. Ahrens, A. Mhl, S. Spors, J. Loh, and K. Bredies. The SoundScape Renderer: A versatile software framework for spatial audio reproduction. In WFS Workshop, Ilmenau, Germany, Sept. 2007.  J. Herder. Sound Spatialization Framework: An Audio Toolkit for Virtual Environments. Journal of the 3D-Forum Society, Japan, 12(3):17-22, 1998.  G. Hiebert. OpenAL 1.1 Specification and Reference, 2005. http://openAL, org.  H. Hoffmann, R. Dachselt, and K. Meissner. An independent declarative 3D audio format on the basis of XML. In ICAD, 2003.  G. S. Kendall. The artistic play of spatial organization: Spatial Attributes, Scene Analysis and Auditory Spatial Schemata. In Proceedings of the 2007 International Computer Music Conference, volume 1, pages 63-68, Copenhagen, Denmark, 2007.  N. Peters, S. Ferguson, and S. McAdams. Towards a Spatial Sound Description Interchange Format (SpatDIF). Cana- K' dian Acoustics, 35(3):64-65, Sept. 2007.  G. Potard and I. Burnett. Using XML Schemas to Create and Encode Interactive 3-D Audio Scenes for Multimedia and Virtual Reality Applications. Lecture Notes In Computer Science, pages 193-203, 2002.  F. Rumsey. Spatial quality evaluation for reproduced sound: Terminology, meaning, and a scene-based paradigm. J. Audio Eng. Soc., 50(9):651-666, 2002.  R. Vaananen and J. Huopaniemi. Advanced AudioBIFS: virtual acoustics modeling in MPEG-4 scene description. IEEE Transactions on Multimedia, 6(5):661-675, 2004........................:..... ii................................................................. i ii:C~.t.i. i:.i... i i:::::::4::::::: \::.............:::44:::::::.......:::::::::::::::::::::::.::: ii:::::: i:'' \4. Figure 1. Several electroacoustic concert venues, from top to down: BEAST UK, IEM Austria, SARC Northern Ireland, ZKM Germany, IRCAM France