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).
asig -- audio signal to be panned
vbap8move 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.
Example 15-1. 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
Ville Pulkki: "Virtual Sound Source Positioning Using Vector Base Amplitude Panning" Journal of the Audio Engineering Society, 1997 June, Vol. 45/6, p. 456.