pvsmaska — Modify amplitudes using a function table, with dynamic scaling.


Modify amplitudes of fsrc using function table, with dynamic scaling.


fsig pvsmaska fsrc, ifn, kdepth


ifn -- The f-table to use. Given fsrc has N analysis bins, table ifn must be of size N or larger. The table need not be normalized, but values should lie within the range 0 to 1. It can be supplied from the score in the usual way, or from within the orchestra by using pvsinfo to find the size of fsrc, (returned by pvsinfo in inbins), which can then be passed to ftgen to create the f-table.


kdepth -- Controls the degree of modification applied to fsrc, using simple linear scaling. 0 leaves amplitudes unchanged, 1 applies the full profile of ifn.

Note that power-of-two FFT sizes are particularly convenient when using table-based processing, as the number of analysis bins (inbins) is then a power-of-two plus one, for which an exactly matching f-table can be created. In this case it is important that the f-table be created with a size of inbins, rather than as a power of two, as the latter will copy the first table value to the guard point, which is inappropriate for this opcode.

[Warning] Warning

It is unsafe to use the same f-variable for both input and output of pvs opcodes. Using the same one might lead to undefined behavior on some opcodes. Use a different one on the left and right sides of the opcode.


Example 364. Example (using score-supplied f-table, assuming fsig fftsize = 1024)

; score f-table using cubic spline to define shaped peaks
f1 0 513 8 0 2 1 3 0 4 1 6 0 10 1 12 0 16 1 32 0 1 0 436 0
asig  buzz     20000,199,50,1        ; pulsewave source
fsig  pvsanal  asig,1024,256,1024,0  ; create fsig
kmod  linseg   0,p3/2,1,p3/2,0       ; simple control sig
fsig2  pvsmaska fsig,2,kmod           ; apply weird eq to fsig
aout  pvsynth  fsig2                  ; resynthesize,
      dispfft  aout,0.1,1024         ; and view the effect


Author: Richard Dobson
August 2001

New in version 4.13