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# vbap4move

vbap4move -- Distributes an audio signal among 4 channels with moving virtual sources.

## Description

Distributes an audio signal among 4 channels with moving virtual sources.

## Syntax

ar1, ar2, ar3, ar4 vbap4move asig, ispread, ifldnum, ifld1 [, ifld2] [...]

## Initialization

ispread -- spreading of the virtual source (range 0 - 100). If value is zero, conventional amplitude panning is used. When ispread is increased, the number of loudspeakers used in panning increases. If value is 100, the sound is applied to all loudspeakers.

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

ifld1, ifld2, ... -- azimuth angles or angular velocities, and relative durations of movement phases (see below).

## Performance

asig -- audio signal to be panned

vbap4move allows the use of moving virtual sources. If ifldnum is positive, the fields represent directions of virtual sources and equal times, iazi1, [iele1,] iazi2, [iele2,], etc. The position of the virtual source is interpolated between directions starting from the first direction and ending at the last. Each interval is interpolated in time that is fraction total_time / number_of_intervals of the duration of the sound event.

If ifldnum 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 polarity of angular velocity is changed. Thus the elevational angular velocity produces a virtual source that moves up and down between 0 and 90 degrees.

## Examples

Example 1. 2-D panning example with stationary virtual sources

      sr      =          4100
      kr      =           441
      ksmps   =           100
      nchnls  =             4
      vbaplsinit         2, 6,  0, 45, 90, 135, 200, 245, 290, 315

              instr 1
      asig    oscil      20000, 440, 1
      a1,a2,a3,a4,a5,a6,a7,a8   vbap8  asig, p4, 0, 20 ;p4 = azimuth

      ;render twice with alternate outq statements
      ;  to obtain two 4 channel .wav files:

              outq       a1,a2,a3,a4
      ;       outq       a5,a6,a7,a8
              endin

## Reference

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

## See Also

vbap16, vbap16move, vbap4, vbap8, vbap8move, vbaplsinit, vbapz, vbapzmove

## Credits

Author: Ville Pulkki
Sibelius Academy Computer Music Studio
Laboratory of Acoustics and Audio Signal Processing
Helsinki University of Technology
Helsinki, Finland
May 2000

New in Csound Version 4.07

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