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< p class = "warning" >
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Ardour's VBAP panner is currently in development, and its semantics may
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change in the near future, possibly affecting mixes using it. It is advised not
to rely on it for important production work while the dust settles.< br / >
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The Panner only works in fixed static mode, it does not support
automation playback.
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< / p >
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< p >
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< dfn > < abbr title = "Vector-base Amplitude Panning" > VBAP< / abbr > < / dfn >
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is a versatile and straightforward method to pan a source around over an
arbitrary number of speakers on a horizontal polygon or a 3D surface,
even if the speaker layout is highly irregular.
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< / p >
< h2 > Basic concepts< / h2 >
< p >
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VBAP was developed by Ville Pulkki at Aalto University, Helsinki, in 1997.
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It works by distributing the signal to the speakers nearest to the desired
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direction with appropriate weightings, aiming to create a maximally sharp
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phantom source by using as few speakers as possible:
< / p >
< ul >
< li > one speaker, if the desired direction coincides with a speaker
location,< / li >
< li > two speakers, if the desired direction is on the line between two
speakers,< / li >
< li > and three speakers in the general 3D case.< / li >
< / ul >
< p >
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Thus, if the panner is moved onto a speaker, only this speaker will get any
signal. This is handy when precise 1:1 routing is needed.
< / p >
< p >
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The drawback of VBAP is that a moving source will constantly change its
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apparent sharpness, as it transitions between the three states mentioned above.
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< / p >
< p >
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An < dfn > horizontal< / dfn > VBAP panner has one parameter, the < dfn > azimuth
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angle< / dfn > . A < dfn > full-sphere< / dfn > panner offers an additional
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< dfn > elevation angle< / dfn > control.
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< / p >
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< p class = "note" >
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More elaborate implementations of VBAP also include a
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< dfn > spread< / dfn > parameter, which will distribute the signal over a
greater number of speakers in order to maintain constant (but no longer
maximal) sharpness, regardless of position. Ardour's VBAP panner does not
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currently include this feature.
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< / p >
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< h2 > Speaker layout< / h2 >
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< figure class = "right" >
< img class = "mini" src = "/images/VBAP-panner-5.png" alt = "The VBAP panner with 5 outputs" >
< figcaption >
The VBAP panner with 5 outputs
< / figcaption >
< / figure >
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< p >
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Each VBAP panner is specific to its < dfn > speaker layout< / dfn > — the
panner has
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to "know" about the precise location of all the speakers. A complete VBAP
implementation must therefore include the possibility to define this
layout.
< / p >
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< p >
Ardour currently uses a simplified approach: if a track or bus has more
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than two output channels (which implies stereo), it assumes that there are
N speakers distributed in a regular N-gon. That means that for
irregular layouts such as 5.1 or 7.1, the direction dialed in will
differ a bit from the actual auditory result, but any desired spatialisation
can still be achieved.
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< / p >
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< h3 class = "clear" > Experimental 3D VBAP< / h3 >
< figure class = "right" >
< img class = "mini" src = "/images/VBAP-panner-10.png" alt = "The VBAP panner with 10 outputs, in experimental 3D mode" >
< figcaption >
The VBAP panner with 10 outputs, in experimental 3D mode
< / figcaption >
< / figure >
<!-- <a href="/images/VBAP - panner - 10.png"><img src="/images/VBAP - panner - 10.png" class="right" style="width:150px;" alt="The VBAP panner with 10 outputs, in experimental 3D mode"></a> -->
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< p >
For tracks with 10 outputs, Ardour will currently assume a 3-dimensional
speaker layout corresponding to Auro-3D 10.1, which is a horizontal 5.1
system, four elevated speakers above L, R, Ls, and Rs, and an additional
"voice-of-god" speaker at the zenith.
< / p >
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< h2 class = "clear" > N:M panning< / h2 >
< figure class = "right" >
< img class = "mini" src = "/images/VBAP-panner-4in5.png" alt = "The VBAP panner in 4 in, 5 out mode" >
< figcaption >
The VBAP panner in 4 in, 5 out mode
< / figcaption >
< / figure >
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< p >
For tracks and busses with more than one input, Ardour will (for now) assume that
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the inputs are distributed symmetrically along the latitude around
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the panner direction. The width parameter controls the opening angle of
the distribution sector.
< / p >