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Why we need SpatDIF:<br><br>There are a lot of different spatailization concepts in even more implementations available (VBAP, Ambisonics, Higher Order Ambisonics, WFS, DBAP, Spatialisateur, Virtual Microphone Control,...) <br><br>We realized that each spatialization algorithm uses a self-contained syntax and data format, wherein sequences of control messages (e.g. trajectories to move a sound in space) programmed for one venue are incompatible with another implementation.<br>Like the recently opened <a href="http://www.mat.ucsb.edu/allosphere/">Allosphere</a> in St. Barbara, more and more concert halls and research facilities are assembled which contain a large number of loudspeakers. Although these venues provide an acoustically optimized environment for 3D audio applications they might differ in terms of room size, their technical specifications and the applied audio rendering concept. Because there is no standardized format for controlling spatialization across different venues and rendering platforms the portability of compositions across venues is complicated because one has to synchronize and convert control data manually.<br>Moreover, software that cannot efficiently interchange information prevents also collaboration between researchers and institutions. Therefore we call for developing of the Spatial Sound Description Interchange format - an open standard to describe spatial audio informations in a structured way in which both real time and non-real time applications are supported.<br><br><ol><li itsalltext_uid="1c311k172s24312z2a27343e2u2z2x342q1i1c37201t1p1p" id="itsalltext_generated_id__1"><b>Coordinate sytstem conventions</b><br><br>We will have to decide whether to use an allocentric (relative to a fixed external framework) or egocentric (relative to the perceiver) perspective (Blesser and Salter, 2006, p. 49), or at least how to distinguish between the two. This will make a difference e.g. in immersive VR applications using binaural audio played back over headphones.<br><br>We will also have to define coordinate system conventions. It is suggested to adapt the system used by Blauert (1996) p. 14: A right-handed Cartesian coordinate system with <i>x</i>- and <i>y</i>-axes forming the horizontal plane, <i>x</i> pointing forward and <i>y</i> to the right. <i>z</i> is the vertical direction, pointing up. Spherical coordinates are definend according to standard mathematical conventions, see e.g. Lossius (2007) p. 12.<br><br></li><li itsalltext_uid="1c311k172s24312z2a27343e2u2z2x342q1i1c37201t1p1p" id="itsalltext_generated_id__1"><b>Description of position:</b><br><br>Position in the three-dimensional space should be described according to a namespace that is not specific to spatialisation only, but also usable e.g. for description of positions in OpenGL. <br><br>Positions should be describable in both Cartesian and spherical coordinates. The UnitLib should offer possibilities for translation between the two:<br>
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/xyz - x-axis y-axis z-axis<br>
/aed - azimuth elevation distance<br>
<br>Absolute positions should be used. The reason for this is that in the case of a source, absolute position is required for air filtering and Doppler shift.<br><br>Proposed syntax describing position for a source:<br><br>Position of sound source #3 in Cartesian coordinates:<br>/source/3/xyz -0.5 0.5 0.0<br> <br>Position of sound source #3 in spherical coordinates<br>/source/3/aed 23.0 0.0 1.0<br><br>If relative positions are to be used, we need to be able to define/describe the unit used (meter or feets).<br>There is a Case in the [UnitLib] page about absolute/relative coordinates for Spatialization<br><br>
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</li><li>Moreover I see the demand to control just one dimension at the time<br><br>e.g.<br><br>/SpatDIF/Src/3/a 23.0 set the azimut of Sound Source 3 to 23 degree<br>/SpatDIF/Src/3/x -0.93 ....<br><br></li><li>the messages in 1. and 2. are absolute values. I think it is really <br>helpfull to have also a possibility to change a message relative to the <br>current position.<br> <br><br>e.g. <br><br>/SpatDIF/Src/3/z- decreases the current z-value of Source 3 by one default unit step<br>/SpatDIF/Src/3/a+ 5 increases the azimut angel by 5 units steps<br> <br>That size of the default unit step must be defined somewhere before.<br>This message is very powerful if you use wildcards in the OSC command: <br>e.g. you could rotate or lift up all sound sources, but keep their <br>spatial relation to each other, by just one command:<br><br>/SpatDIF/Src/*/a+ 5 <br>/SpatDIF/Src/*/z-<br><br><b>Comments: </b>Can be done using :inc and :dec<br><br>Number of steps added to the feature tracker</li>
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<li><b>Loudspeaker</b><br><br>usually the spatialisation algorithm has to know where the speakers are placed to apply the right signal to each loudspeaker.<br>
Loudspeakers should be defined in absolute coordinates, as every other parameter.<br>
There is a Case in the [UnitLib] page about absolute/relative coordinates for Spatialization, because we may wish to define positions using "natural" units such as meters... The reference point is also metionned on this page (as noticed by Nils : When I think about Trond's DBAP where you don't have a reference
point/sweet spot in the middle of your speaker layout, you might also
want to set the speaker from a self-defined point in your listening room.)<br>
While loudspeakers don't usually remain static, this could not be the case... and we could use virtual (moving) loudspeakers for doing FX sends as does Mathieu in his system.<br>
<br></li>
<li><b>List of possible spatialization parameters : </b><br>
<b> Technical parameters : </b><br>
for sources : position (together : /xyz or /aed or separately : /x, /y, /e, etc...), position shift (:inc), spread ? ...<br>
for loudspeakers : position...<br>
<b> Perceptual parameters : </b><br>
<br></li>
</ol>
<br><h2>References:</h2>Peters N. , Ferguson S. and McAdams S.: <a href="http://www.music.mcgill.ca/%7Enils/papers/CAA2007_Peters_et_al-SpatDIF.pdf">"Towards a Spatial Sound Description Interchange Format (SpatDIF)"</a>, to appear in Proc. of the 2007 Annual Conference of the Canadian Acoustical Association, Montreal, Oct. 2007<br><br>SpatDIF proposal presentation at the Jamoma Spatialization workshop 2007 in Bergen by Nils Peters--> ask Trond or Nils <br><br>Blauert, J. (1996): Spatial hearing. The psychoacoustics of human sound localization. Revised edition. The MIT Press.<br><br>Blesser, B. & L.R. Salter (2007): Spaces speak, are you listening? Experiencing aural architecture. The MIT Press.<br><br>Lossius, T. (2007): <a href="http://www.bek.no/%7Elossius/text/fellowship_report.pdf">Sound - Space - Body. Reflections on artistic practice.</a> Thesis in partial fulfillment of the research fellowship in the arts. Bergen National Academy of the Arts.<br><br>Zbyszyski M. and Freed A.: <a href="http://www.cnmat.berkeley.edu/ICMC2005/pdf/zbyszynski_ICMC3.pdf">Control of VST plug-ins using OSC</a>. In Proceedings of the International Computer Music Conference, pages 263–266, Barcelona, Spain, 2005.<br><br><br><br>
<li>Moved Points :<br>
The old proposal about position and the point about the active flags have been moved to : [Spatialization : Archived Discussions]<br>
The point about starttime has been moved to [Cue Management]<br>
The point about ramps in :+/:inc, has been moved to the [Ramp Lib] and added to the feature tracker.<br>
</li>
