Overview
Table driven interpolation module. Supports linear and spline modes
Discussion
This module performs table lookup using unevenly spaced X and Y values. The module supports linear and pchip interpolation. Internally the interpolation is performed using a piece wise polynomial approximation. With linear interpolation a first order polynomial is used; for pchip a 4th order polynomial is used. PChip is similar to a spline interpolation but it avoids the overshoot and undershoot that plagues splines.
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The X values in the table have to monotonically increasing. That is, x0 < x1 < x2 < ... < xN. If this condition is not obeyed, then the module's prebuild function will generate an error.
Type Definition
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typedef struct _ModuleTableInterp
{
ModuleInstanceDescriptor instance; // Common Audio Weaver module instance structure
INT32 maxPoints; // Maximum number of values in the lookup table. The total table size is [maxPoints 2].
INT32 numPoints; // Current number of interpolation values in use.
INT32 order; // Order of the interpolation. This can be either 2 (for linear) or 4 (for pchip).
FLOAT32* XY; // Lookup table. The first row is the X values and the second row is the Y values.
FLOAT32* polyCoeffs; // Interpolation coefficients returned by the grid control.
} ModuleTableInterpClass; |
Variables
Properties
Name | Type | Usage | isHidden | Default value | Range | Units |
maxPoints | int | const | 0 | 8 | 4:1:1000 | |
numPoints | int | parameter | 0 | 4 | 4:1:8 | |
order | int | parameter | 0 | 2 | 2:2:4 | |
XY | float* | parameter | 0 | [2 x 8] | Unrestricted | |
polyCoeffs | float* | state | 0 | [4 x 7] | Unrestricted |
Pins
Input Pins
Name: in
Description: audio input
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Sample rate range: Unrestricted
Complex support: Real
Output Pins
Name: out
Description: audio output
Data type: float
MATLAB Usage
File Name: table_interp_module.m
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