Db20Fract32

Overview

Converts from linear units to decibels using a polynomial approximation

Discussion

Converts from linear units to decibels (db20) using a polynomial approximation. The input format is Q9.23 (values in the range +/- 128) and the output format is Q9.23 also (values in the range +/- 128). The function computes the absolute value of the input before computing the log. The output will always be in the range [48.16 -198.4738]. The results are accurate to within 8e-3 (in Q9.23).

For negative inputs the function takes the absolute value. An input of 0 returns -256.

Module Pack

Standard

ClassID

classID = 141

Type Definition

typedef struct _ModuleDb20Fract32
{
ModuleInstanceDescriptor instance;            // Common Audio Weaver module instance structure
} ModuleDb20Fract32Class;

Pins

Input Pins


Name	in
Description	Input signal
Data type	fract32
Channel range	Unrestricted
Block size range	Unrestricted
Sample rate range	Unrestricted
Complex support	Real

Output Pins


Name	out
Description	Output signal
Data Type	fract32

Matlab Usage

File Name: db20_fract32_module.m 
 M=db20_fract32_module(NAME) 
 Creates an Audio Weaver module that computes the function 20*log10(abs(x)) 
 using a polynomial approximation.  The input and the output are Q9.23. 
 Arguments: 
    NAME - name of the module.