parent
3605d6b6a8
commit
4cf6145888
@ -1,89 +0,0 @@ |
||||
/*
|
||||
* DCfilter.h |
||||
* |
||||
* Copyright 2012 Tim Barrass. |
||||
* |
||||
* This file is part of Mozzi. |
||||
* |
||||
* Mozzi is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. |
||||
* |
||||
*/ |
||||
|
||||
#ifndef DCFILTER_H |
||||
#define DCFILTER_H |
||||
|
||||
/*
|
||||
tb2010 adapted from: |
||||
robert bristow-johnson, DSP Trick: Fixed-Point DC Blocking Filter with Noise-Shaping |
||||
http://www.dspguru.com/book/export/html/126
|
||||
|
||||
y[n] = x[n] - x[n-1] + a * y[n-1] |
||||
|
||||
Where y[n] is the output at the current time n, and x[n] is the input at the current time n. |
||||
|
||||
also, see DC Blocker Algorithms, http://www.ingelec.uns.edu.ar/pds2803/materiales/articulos/04472252.pdf
|
||||
*/ |
||||
|
||||
/**
|
||||
A DC-blocking filter useful for highlighting changes in control signals. |
||||
The output of the filter settles to 0 if the incoming signal stays constant. If the input changes, the |
||||
filter output swings to track the change and eventually settles back to 0. |
||||
*/ |
||||
class DCfilter |
||||
{ |
||||
public: |
||||
/**
|
||||
Instantiate a DC-blocking filter. |
||||
@param pole sets the responsiveness of the filter, |
||||
how long it takes to settle to 0 if the input signal levels out at a constant value. |
||||
*/ |
||||
DCfilter(float pole):acc(0),prev_x(0),prev_y(0) |
||||
{ |
||||
A = (int)(32768.0*(1.0 - pole)); |
||||
} |
||||
|
||||
/* almost original
|
||||
// timing: 20us
|
||||
int next(int x) |
||||
{ |
||||
setPin13High(); |
||||
acc -= prev_x; |
||||
prev_x = (long)x<<15; |
||||
acc += prev_x; |
||||
acc -= A*prev_y; |
||||
prev_y = acc>>15; // quantization happens here
|
||||
int filtered = (int)prev_y; |
||||
// acc has y[n] in upper 17 bits and -e[n] in lower 15 bits
|
||||
setPin13Low(); |
||||
return filtered; |
||||
} |
||||
*/ |
||||
|
||||
/**
|
||||
Filter the incoming value and return the result. |
||||
@param x the value to filter |
||||
@return filtered signal |
||||
*/ |
||||
// timing :8us
|
||||
inline |
||||
int next(int x) |
||||
{ |
||||
acc += ((long)(x-prev_x)<<16)>>1; |
||||
prev_x = x; |
||||
acc -= (long)A*prev_y; // acc has y[n] in upper 17 bits and -e[n] in lower 15 bits
|
||||
prev_y = (acc>>16)<<1; // faster than >>15 but loses bit 0
|
||||
if (acc & 32784) prev_y += 1; // adds 1 if it was in the 0 bit position lost in the shifts above
|
||||
return prev_y; |
||||
} |
||||
|
||||
private: |
||||
long acc; |
||||
int prev_x, prev_y,A; |
||||
}; |
||||
|
||||
/**
|
||||
@example 05.Control_Filters/DCFilter/DCFilter.ino |
||||
This example demonstrates the DCFilter class. |
||||
*/ |
||||
|
||||
#endif // #ifndef DCFILTER_H
|
||||
@ -1,44 +0,0 @@ |
||||
/*
|
||||
============================================================================== |
||||
This file is part of Tal-NoiseMaker by Patrick Kunz. |
||||
|
||||
Copyright(c) 2005-2010 Patrick Kunz, TAL |
||||
Togu Audio Line, Inc. |
||||
http://kunz.corrupt.ch
|
||||
|
||||
This file may be licensed under the terms of of the |
||||
GNU General Public License Version 2 (the ``GPL''). |
||||
|
||||
Software distributed under the License is distributed |
||||
on an ``AS IS'' basis, WITHOUT WARRANTY OF ANY KIND, either |
||||
express or implied. See the GPL for the specific language |
||||
governing rights and limitations. |
||||
|
||||
You should have received a copy of the GPL along with this |
||||
program. If not, go to http://www.gnu.org/licenses/gpl.html
|
||||
or write to the Free Software Foundation, Inc., |
||||
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. |
||||
============================================================================== |
||||
*/ |
||||
|
||||
#if !defined(__OnePoleLP_h) |
||||
#define __OnePoleLP_h |
||||
|
||||
class OnePoleLP { |
||||
public: |
||||
float inputs, outputs, lastOutput; |
||||
|
||||
OnePoleLP() { |
||||
lastOutput = inputs = outputs = 0.0f; |
||||
} |
||||
|
||||
~OnePoleLP() {} |
||||
|
||||
void tick(float *sample, float cutoff) { |
||||
float p = (cutoff * 0.98f) * (cutoff * 0.98f) * (cutoff * 0.98f) * (cutoff * 0.98f); |
||||
outputs = (1.0f - p) * (*sample) + p * outputs; |
||||
*sample = outputs; |
||||
} |
||||
}; |
||||
|
||||
#endif |
||||
Loading…
Reference in new issue