TableLookupLogX

Overview

Log/Anti-log and Linearly spaced table lookup

Discussion

Multichannel input / multichannel output table lookup module. The table lookup is Log, Anti-log or Linear spaced, using a variety of interpolation methods. The module performs lookup as Y=f(X) where X is the input to the module and Y is the output. The module contains a table of values which are assumed to be Log, Anti-log or linearly spaced. The first value in the table corresponds to the function value at .minX. The last value in the table corresponds to the function value at .maxX. The field .interpolationType determines how the interpolation occurs.

.interpolationType = 0 - output the nearest value .interpolationType = 1 - linear interpolation between the two nearest values.

Input values outside of the range [minX maxX] are clipped.

Type Definition

CODE

typedef struct _ModuleTableLookupLogX
{
    ModuleInstanceDescriptor instance;            // Common Audio Weaver module instance structure
    INT32 numPoints;                              // Number of entries in the table.
    INT32 spacingType;                            // Selects the input spacig type: 0=Log, 1=Anti-log and 2=Linear.
    INT32 interpolationType;                      // Selects the type of interpolation: 0=nearest, 1=linear.
    FLOAT32 minX;                                 // X value corresponding to the first table entry.
    FLOAT32 maxX;                                 // X value corresponding to the last table entry.
    FLOAT32 log_minX;                             // Log value of the minX parameter.
    FLOAT32 log_maxX;                             // Log value of the maxX parameter.
    FLOAT32 logspace_delta;                       // Logspace delta for input.
    FLOAT32 divisor;                              // Precomputed constant = (NUM_POINTS-1)/(log_maxX - log_minX) to eliminate division on the target.
    FLOAT32* table;                               // Table of evenly spaced values.
} ModuleTableLookupLogXClass;

Variables

Properties

Name	Type	Usage	isHidden	Default value	Range	Units
numPoints	int	const	0	10	2:1:5000
spacingType	int	const	0	0	0:2:1
interpolationType	int	parameter	0	1	0:1:1
minX	float	parameter	0	1	-1000:1000
maxX	float	parameter	0	10	-1000:1000
log_minX	float	state	0	0	Unrestricted
log_maxX	float	state	0	0	Unrestricted
logspace_delta	float	state	0	0	Unrestricted
divisor	float	state	0	0	Unrestricted
table	float*	parameter	0	[10 x 1]	Unrestricted

Pins

Input Pins

Name: in

Description: audio input

Data type: float

Channel range: Unrestricted

Block size range: 1

Sample rate range: Unrestricted

Complex support: Real

Output Pins

Name: out

Description: audio output

Data type: float

MATLAB Usage

File Name: table_lookup_logx_module.m

CODE

 M=table_lookup_logx_module(NAME, NUM_POINTS, SPACING)
 Creates a table lookup module for use in the Audio Weaver environment. 
 This module has 1 multichannel input and 1 multichannel output and performs
 log/anti-log or liniear spaced table lookup using nearest or linear interpolation scheme.  
 
 Arguments:
    NAME - name of the module.
    NUM_POINTS - size of the table.
    SPACING - Log/Anti-log or linear spacing on inputs. 0 - Log, 1 -
    Anti-log and 2 - Linear
 The module performs lookup as Y=f(X) where X is the input to the module
 and Y is the output. The module contains a table of values which are
 assumed to be Log/Anti-log or linearly spaced. The first value in the table corresponds
 to the function value at .minX. The last value in the table corresponds
 to the function value at .maxX. The field .interpolationType determines
 how the interpolation occurs.
   .interpolationType = 0, output the nearest value.
   .interpolationType = 1, linear interpolation between the two nearest
                           values.
 Input values outside of the range [minX maxX] are clipped.