The Alternative Csound Reference Manual
Previous |  | Next

# pvsmaska

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

## Description

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

## Syntax

fsig pvsmaska fsrc, ifn, kdepth

## Initialization

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.

## Performance

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.

## Examples

Example 1. 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     20000,199,50,3        ; pulsewave source
    fsig  pvsanal  asig,1024,256,1024,0  ; create fsig
    kmod  linseg   0,p3/2,1,p3/2,0       ; simple control sig

    fsig  pvsmaska fsig,2,kmod           ; apply weird eq to fsig
    aout  pvsynth  fsig                  ; resynthesize,
          dispfft  aout,0.1,1024         ; and view the effect

This also illustrates that the usual Csound behaviour applies to fsigs; the same name can be used for both input and output.

## Credits

Author: Richard Dobson
August 2001

New in version 4.13

Previous | Home | Next
pvsinfo | Up | pvsynth