Jamoma API  0.6.0.a19
TTLowpassButterworth4.h
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1 /** @file
2  *
3  * @ingroup dspFilterLib
4  *
5  * @brief #TTLowpassButterworth4 is a fourth-order Butterworth lowpass filter.
6  *
7  * @details Butterworth filters have maximum flat frequency response in the pass band.
8  * @n
9  * Filter equations from: @n
10  * @n
11  * Second-order IIR Filters will support cascade implementations @n
12  * By Rusty Allred, Texas Instruments, Dallas @n
13  * July 01, 2003 @n
14  * http://www.planetanalog.com/article/printableArticle.jhtml?articleID=12802683
15  *
16  * @authors Trond Lossius, Timothy Place,
17  *
18  * @copyright Copyright © 2008, Trond Lossius @n
19  * This code is licensed under the terms of the "New BSD License" @n
20  * http://creativecommons.org/licenses/BSD/
21  */
22 
23 
24 #ifndef __TT_LOWPASS_BUTTERWORTH_4_H__
25 #define __TT_LOWPASS_BUTTERWORTH_4_H__
26 
27 #include "TTDSP.h"
28 
29 
30 /** 4th order Butterworth lowpass filter; Butterworth filters have maximum flat frequency response in the pass band.
31  *
32  * Filter equations from:
33  *
34  * Second-order IIR Filters will support cascade implementations
35  * By Rusty Allred, Texas Instruments, Dallas
36  * July 01, 2003
37  * http://www.planetanalog.com/article/printableArticle.jhtml?articleID=12802683
38  *
39  */
42 
43 protected:
44 
45  TTFloat64 mFrequency; ///< filter cutoff frequency
46  TTFloat64 mK, mK2,mK3,mK4, mRadians, mRadians2, mRadians3, mRadians4; ///< filter coefficients
47  TTFloat64 mA0, mA1, mA2; ///< filter coefficients for input samples
48  TTFloat64 mB1, mB2, mB3, mB4; ///< filter coefficients for output samples
49  TTSampleVector mX1; ///< Input sample n-1
50  TTSampleVector mX2; ///< Input sample n-2
51  TTSampleVector mX3; ///< Input sample n-3
52  TTSampleVector mX4; ///< Input sample n-4
53  TTSampleVector mY1; ///< Output sample n-1
54  TTSampleVector mY2; ///< Output sample n-2
55  TTSampleVector mY3; ///< Output sample n-3
56  TTSampleVector mY4; ///< Output sample n-4
57 
58  /** Receives notifications when there are changes to the inherited
59  mMaxNumChannels attribute. This allocates memory for xm1, xm2, ym1, and ym2
60  so that each channel's previous values are remembered. */
61  TTErr updateMaxNumChannels(const TTValue& oldMaxNumChannels, TTValue&);
62  TTErr updateSampleRate(const TTValue& oldSampleRate, TTValue&);
63 
64  /** This algorithm uses an IIR filter, meaning that it relies on feedback. If the filter should
65  * not be producing any signal (such as turning audio off and then back on in a host) or if the
66  * feedback has become corrupted (such as might happen if a NaN is fed in) then it may be
67  * neccesary to clear the filter by calling this method.
68  * @return Returns a TTErr error code. */
69  TTErr clear();
70 
71  void calculateCoefficients();
72 
73  /** Standard single value calculate method as used by DSP objects. */
74  inline TTErr calculateValue(const TTFloat64& x, TTFloat64& y, TTPtrSizedInt channel);
75 
76  /** Standard audio processing method as used by TTBlue objects. */
78 
79  /** Setter for the frequency attribute. */
80  TTErr setFrequency(const TTValue& value);
81 
82 
83  /** Unit Tests
84  @param returnedTestInfo Used to return test information
85  @return #TTErr error code if the method fails to execute, else #kTTErrNone.
86  */
87  virtual TTErr test(TTValue& returnedTestInfo);
88 };
89 
90 
91 
92 #endif // __TT_LOWPASS_BUTTERWORTH_4_H__
TTFloat64 mFrequency
filter cutoff frequency
TTAudioObjectBase is the base class for all audio generating and processing objects in Jamoma DSP...
TTErr calculateValue(const TTFloat64 &x, TTFloat64 &y, TTPtrSizedInt channel)
Standard single value calculate method as used by DSP objects.
virtual TTErr test(TTValue &returnedTestInfo)
Unit Tests.
Jamoma DSP Library.
double TTFloat64
64 bit floating point number
Definition: TTBase.h:188
TTErr setFrequency(const TTValue &value)
Setter for the frequency attribute.
TTErr processAudio(TTAudioSignalArrayPtr inputs, TTAudioSignalArrayPtr outputs)
Standard audio processing method as used by TTBlue objects.
#define TTCLASS_SETUP(className)
TODO Doxygen: need more comments here.
Definition: TTFoundation.h:54
TTSampleVector mY2
Output sample n-2.
4th order Butterworth lowpass filter; Butterworth filters have maximum flat frequency response in the...
std::vector< TTSampleValue > TTSampleVector
A TTSampleVector is simply a pointer to the first of an array of TTSampleValues.
Definition: TTBase.h:233
TTSampleVector mX1
Input sample n-1.
TTSampleVector mY4
Output sample n-4.
TTSampleVector mY1
Output sample n-1.
A simple container for an array of TTAudioSignal pointers.
long TTPtrSizedInt
An integer that is the same size as a pointer.
Definition: TTBase.h:240
TTErr
Jamoma Error Codes Enumeration of error codes that might be returned by any of the TTBlue functions a...
Definition: TTBase.h:342
TTErr updateMaxNumChannels(const TTValue &oldMaxNumChannels, TTValue &)
Receives notifications when there are changes to the inherited mMaxNumChannels attribute.
TTSampleVector mX3
Input sample n-3.
TTSampleVector mY3
Output sample n-3.
TTFloat64 mRadians4
filter coefficients
TTSampleVector mX4
Input sample n-4.
TTSampleVector mX2
Input sample n-2.
TTFloat64 mB4
filter coefficients for output samples
TTFloat64 mA2
filter coefficients for input samples
[doxygenAppendixC_copyExample]
Definition: TTValue.h:34
TTErr clear()
This algorithm uses an IIR filter, meaning that it relies on feedback.