SbDerivative

Overview

Subband derivative

Discussion

Computes the derivative of frequency domain data individually within each subband. The derivative is defined as:

\(y[n] = K/T * (x[n] - x[n-1])\) where T is the sample period and K is the optional gain parameter. The module sets the default starting value to x[-1] = 0.

The discrete derivative is similar to the continuous time derivative. For example, if the input is a sine wave at 1 kHz, then the output will be a cosine at 1 kHz scaled by 2pi1000.

The hidden internal array .lastValue stores the previous value x[n-1] between blocks. The length of the array is set by the prebuild function to the number of subbands.

Module Pack

Advanced

ClassID

classID = 1324

Type Definition

typedef struct _ModuleSbDerivative
{
ModuleInstanceDescriptor instance;            // Common Audio Weaver module instance structure
FLOAT32 gain;                                 // Additional gain.
FLOAT32* lastValue;                           // Previous value x[n-1].
} ModuleSbDerivativeClass;

Variables

Properties

Name	Type	Usage	isHidden	Default Value	Range	Units
gain	float	parameter	0	1	-10:10	linear
lastValue	float*	state	1	[32 x 1]	Unrestricted

Pins

Input Pins


Name	in
Description	audio input
Data type	float
Channel range	Unrestricted
Block size range	Unrestricted
Sample rate range	Unrestricted
Complex support	Real

Output Pins


Name	out
Description	audio output
Data Type	float

Matlab Usage

File Name: sb_derivative_module.m 
 M=sb_derivative_module(NAME) 
 Subband derivative module in which the derivative value of each  
 subband is separately computed.  The module only operates on real 
 data and mathematically computes: 
   y[n] = 1/dt * (x[n] - x[n-1]) 
 where dt is the time step, dt = 1/SR.  The module has a multichannel 
 input and computes the derivative per channel.  Arguments: 
    NAME - name of the module.