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GEN Routines: Amplitude Scaling

GEN04

  f  #  time  size  4  source#  sourcemode   

Description

This subroutine generates a normalizing function by examining the contents of an existing table.

Initialization

size – number of points in the table. Should be power-of-2 plus 1. Must not exceed (except by 1) the size of the source table being examined; limited to just half that size if the sourcemode is of type offset (see below).

source # – table number of stored function to be examined.

sourcemode – a coded value, specifying how the source table is to be scanned to obtain the normalizing function. Zero indicates that the source is to be scanned from left to right. Non-zero indicates that the source has a bipolar structure; scanning will begin at the mid-point and progress outwards, looking at pairs of points equidistant from the center.

Note

The normalizing function derives from the progressive absolute maxima of the source table being scanned. The new table is created left-to-right, with stored values equal to 1/(absolute maximum so far scanned). Stored values will thus begin with 1/(first value scanned), then get progressively smaller as new maxima are encountered. For a source table which is normalized (values <= 1), the derived values will range from 1/(first value scanned) down to 1. If the first value scanned is zero, that inverse will be set to 1.

The normalizing function from GEN04 is not itself normalized.

GEN04 is useful for scaling a table-derived signal so that it has a consistent peak amplitude. A particular application occurs in waveshaping when the carrier (or indexing) signal is less than full amplitude.

Example

  f   2   0   512   4    1   1   

This creates a normalizing function for use in connection with the GEN03 table 1 example. Midpoint bipolar offset is specified.


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GEN Routines: Amplitude Scaling