vbaplsinit, vbapl4, vbapl8, vbapl4move, vbapl8move, 

 
                   vbaplsinit  idim, ils_amount, idir1, idir2,... 

 a1, a2, a3, a4    vbapl4      asig, iazi,iele
 a1, a2, a3, a4, 
  a5, a6, a7, a8   vbapl8      asig, iazi,iele

 a1, a2, a3, a4    vbapl4move  asig, ifld_amount, ifld1, ifld2, ...
 a1, a2, a3, a4, 
  a5, a6, a7, a8   vbapl8move  asig, ifld_amount, ifld1, ifld2, ...
Distribute an audio signal amongst two to eight channels with localization control.

INITIALIZATION

idim - dimensionality, 2 or 3.

ils_amount - number of loudspeakers. In two dimensions the number can vary between two to eight. In three dimensions the number can vary between three and eight.

idirn - directions of loudspeakers, number of directions must be less or equal than 8. In two-dimensional loudspeaker positioning idirn is the azimuth angle respective to nth channel. In three-dimensional loudspeaker positioning fields are the azimuth and elevation angles of each loudspeaker consequently (azi1, ele1, azi2, ele2,...).

asig - audio signal to be panorated.

iazi - azimuth angle of the virtual source.

iele - elevation angle of the virtual source

ifld_amount - number of fields (absolute value must be 2 or larger). If ifld_amount is positive, the virtual source movement is a polyline specified by given directions, each transition is performed in an equal time interval. If ifld_amount is negative, specified angular velocities are applied to the virtual source during specified relative time intervals (see below).

ifldn - Azimuth angles or angular velocities, and relative durations of movement phases (see below).

PERFORMANCE

vbapl4 and vbapl8 take an input signal asig and distribute it amongst at two to eight outputs according to the controls iazi and iele and configured loudspeaker placement. If idim = 2, iele is set to zero. The distribution is performed using Vector Base Amplitude Panning (VBAP) [1]. VBAP distributes the signal using loudspeaker data configured with vbaplsinit. The signal is applied at most to two loudspeakers in 2-D loudspeaker configurations and to three loudspeakers in 3-D loudspeaker configurations. If the virtual source is panned outside the region spanned by loudspeakers, a warning signal is given and the signal may be muted.

vbapl4move and vbapl8move allow moving virtual sources to be applied. If ifld_amount is positive, the fields represent directions of virtual sources and equal times, iazi1, [iele1,] iazi2, [iele2,] .... The position of the virtual source is interpolated between directions starting from first direction and ending to last. Each interval is interpolated in time that is fraction total_time / number_of_intervals of the duration of the sound event.

If ifld_amount is negative, the fields represent angular velocities and equal times. The first field is however the starting direction, iazi1, [iele1,] iazi_vel1, [iele_vel1,] iazi_vel2, [iele_vel2,] .... Each velocity is applied to the note that is fraction total_time / number_of_velocities of the duration of the sound event. If the elevation of the virtual source becomes greater than 90 degrees or less than 0 degrees, the angular velocity is negated. Thus the elevational angular velocity produces a virtual source that moves up and down between 0 and 90 degrees.

2-D panning example with stationary virtual sources


         sr = 44100
         kr = 441
         ksmps = 100
         nchnls = 4
         vbaplsinit 2, 6,  0, 45, 90, 135, 200, 315, 
         instr     1	                             ;parameter
	 asig oscil 20000, 440, 1                    ; p4 = azimuth 
a1, a2, a3, a4, a5, a6, a7, a8	vbapl8	asig, p4, 0  
	 outq     a1,a2,a3,a4
;        outq     a5,a6,a7,a8
         endin

3-D panning example with angular velocities

3-D panning example with direction-to-direction movement

References

[1] Ville Pulkki: Virtual Sound Source Positioning Using Vector Base Amplitude Panning. Journal of the Audio Engineering Society, 1997 June, Vol. 45/6, p. 456. 

Implementation by Ville Pulkki
Sibelius Academy Computer Music Studio
Laboratory of Acoustics and Audio Signal Processing 
Helsinki University of Technology
August 1998
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