parasiTstudio
/
BALibrary_parasitstudio
forked from wirtz/BALibrary
3
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

Merge pull request #2 from Blackaddr/feature/sjl/addCustomFilters

Browse Source 
Feature/sjl/add custom filters
master
Blackaddr Audio 7 years ago committed by GitHub
parent 354cd93bab 9c836553de
commit 07d9112aaa
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
4 changed files with 123 additions and 21 deletions
Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL
Show Stats Download Patch File Download Diff File
  1. 7
      examples/Delay/AnalogDelayDemo/AnalogDelayDemo.ino
  2. 25
      src/AudioEffectAnalogDelay.h
  3. 29
      src/effects/AudioEffectAnalogDelay.cpp
  4. 83
      src/effects/AudioEffectAnalogDelayFilters.h

7
examples/Delay/AnalogDelayDemo/AnalogDelayDemo.ino
Unescape View File

@ -94,6 +94,13 @@ void setup() {
analogDelay.mix(0.5f);
analogDelay.feedback(0.0f);
//////////////////////////////////
// AnalogDelay filter selection //
// Uncomment to tryout the 3 different built-in filters.
//analogDelay.setFilter(AudioEffectAnalogDelay::Filter::DM3); // The default filter. Naturally bright echo (highs stay, lows fade away)
//analogDelay.setFilter(AudioEffectAnalogDelay::Filter::WARM); // A warm filter with a smooth frequency rolloff above 2Khz
//analogDelay.setFilter(AudioEffectAnalogDelay::Filter::DARK); // A very dark filter, with a sharp rolloff above 1Khz
// Setup 2-stages of LPF, cutoff 4500 Hz, Q-factor 0.7071 (a 'normal' Q-factor)
cabFilter.setLowpass(0, 4500, .7071);
cabFilter.setLowpass(1, 4500, .7071);

25
src/AudioEffectAnalogDelay.h
Unescape View File

@ -30,10 +30,6 @@
namespace BAGuitar {
/// The number of stages in the analog-response Biquad filter
constexpr unsigned MAX_NUM_FILTER_STAGES = 4;
constexpr unsigned NUM_COEFFS_PER_STAGE = 5;
/**************************************************************************//**
* AudioEffectAnalogDelay models BBD based analog delays. It provides controls
* for delay, feedback (or regen), mix and output level. All parameters can be
@ -54,6 +50,12 @@ public:
NUM_CONTROLS ///< this can be used as an alias for the number of MIDI controls
};
enum class Filter {
DM3 = 0,
WARM,
DARK
};
// *** CONSTRUCTORS ***
AudioEffectAnalogDelay() = delete;
@ -133,9 +135,17 @@ public:
/// @param value the CC value from 0 to 127
void processMidi(int channel, int midiCC, int value);
// ** FILTER COEFFICIENTS **
/// Set the filter coefficients to one of the presets. See AudioEffectAnalogDelay::Filter
/// for options.
/// @details See AudioEffectAnalogDelayFIlters.h for more details.
/// @param filter the preset filter. E.g. AudioEffectAnalogDelay::Filter::WARM
void setFilter(Filter filter);
/// Override the default coefficients with your own. The number of filters stages affects how
/// much CPU is consumed.
/// @details The effect uses the CMSIS-DSP library for biquads which requires coefficents
/// @details The effect uses the CMSIS-DSP library for biquads which requires coefficents.
/// be in q31 format, which means they are 32-bit signed integers representing -1.0 to slightly
/// less than +1.0. The coeffShift parameter effectively multiplies the coefficients by 2^shift. <br>
/// Example: If you really want +1.5, must instead use +0.75 * 2^1, thus 0.75 in q31 format is
@ -171,11 +181,6 @@ private:
// Coefficients
void m_constructFilter(void);
// int m_numStages;
// int m_coeffShift;
// int m_coeffs[MAX_NUM_FILTER_STAGES*NUM_COEFFS_PER_STAGE] = {};
//size_t m_callCount = 0;
};
}

29
src/effects/AudioEffectAnalogDelay.cpp
Unescape View File

@ -5,6 +5,7 @@
* Author: slascos
*/
#include <new>
#include "AudioEffectAnalogDelayFilters.h"
#include "AudioEffectAnalogDelay.h"
namespace BAGuitar {
@ -12,16 +13,6 @@ namespace BAGuitar {
constexpr int MIDI_CHANNEL = 0;
constexpr int MIDI_CONTROL = 1;
// BOSS DM-3 Filters
constexpr unsigned DM3_COEFF_SHIFT = 2;
constexpr int32_t DM3[5*MAX_NUM_FILTER_STAGES] = {
536870912, 988616936, 455608573, 834606945, -482959709,
536870912, 1031466345, 498793368, 965834205, -467402235,
536870912, 1105821939, 573646688, 928470657, -448083489,
2339, 5093, 2776, 302068995, 4412722
};
AudioEffectAnalogDelay::AudioEffectAnalogDelay(float maxDelayMs)
: AudioStream(1, m_inputQueueArray)
{
@ -58,7 +49,7 @@ AudioEffectAnalogDelay::~AudioEffectAnalogDelay()
void AudioEffectAnalogDelay::m_constructFilter(void)
{
// Use DM3 coefficients by default
m_iir = new IirBiQuadFilterHQ(MAX_NUM_FILTER_STAGES, reinterpret_cast<const int32_t *>(&DM3), DM3_COEFF_SHIFT);
m_iir = new IirBiQuadFilterHQ(DM3_NUM_STAGES, reinterpret_cast<const int32_t *>(&DM3), DM3_COEFF_SHIFT);
}
void AudioEffectAnalogDelay::setFilterCoeffs(int numStages, const int32_t *coeffs, int coeffShift)
@ -66,6 +57,22 @@ void AudioEffectAnalogDelay::setFilterCoeffs(int numStages, const int32_t *coeff
m_iir->changeFilterCoeffs(numStages, coeffs, coeffShift);
}
void AudioEffectAnalogDelay::setFilter(Filter filter)
{
switch(filter) {
case Filter::WARM :
m_iir->changeFilterCoeffs(WARM_NUM_STAGES, reinterpret_cast<const int32_t *>(&WARM), WARM_COEFF_SHIFT);
break;
case Filter::DARK :
m_iir->changeFilterCoeffs(DARK_NUM_STAGES, reinterpret_cast<const int32_t *>(&DARK), DARK_COEFF_SHIFT);
break;
case Filter::DM3 :
default:
m_iir->changeFilterCoeffs(DM3_NUM_STAGES, reinterpret_cast<const int32_t *>(&DM3), DM3_COEFF_SHIFT);
break;
}
}
void AudioEffectAnalogDelay::update(void)
{
audio_block_t *inputAudioBlock = receiveReadOnly(); // get the next block of input samples

83
src/effects/AudioEffectAnalogDelayFilters.h
Unescape View File

@ -0,0 +1,83 @@
/**************************************************************************//**
* @file
* @author Steve Lascos
* @company Blackaddr Audio
*
* This file constains precomputed co-efficients for the AudioEffectAnalogDelay
* class.
*
* @copyright This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.*
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*****************************************************************************/
#include <cstdint>
namespace BAGuitar {
// The number of stages in the analog-response Biquad filter
constexpr unsigned MAX_NUM_FILTER_STAGES = 4;
constexpr unsigned NUM_COEFFS_PER_STAGE = 5;
// Matlab/Octave can be helpful to design a filter. Once you have the IIR filter (bz,az) coefficients
// in the z-domain, they can be converted to second-order-sections. AudioEffectAnalogDelay is designed
// to accept up to a maximum of an 8th order filter, broken into four, 2nd order stages.
//
// Second order sections can be created with:
// [sos] = tf2sos(bz,az);
// The results coefficents must be converted the Q31 format required by the ARM CMSIS-DSP library. This means
// all coefficients must lie between -1.0 and +0.9999. If your (bz,az) coefficients exceed this, you must divide
// them down by a power of 2. For example, if your largest magnitude coefficient is -3.5, you must divide by
// 2^shift where 4=2^2 and thus shift = 2. You must then mutliply by 2^31 to get a 32-bit signed integer value
// that represents the required Q31 coefficient.
// BOSS DM-3 Filters
// b(z) = 1.0e-03 * (0.0032 0.0257 0.0900 0.1800 0.2250 0.1800 0.0900 0.0257 0.0032)
// a(z) = 1.0000 -5.7677 14.6935 -21.3811 19.1491 -10.5202 3.2584 -0.4244 -0.0067
constexpr unsigned DM3_NUM_STAGES = 4;
constexpr unsigned DM3_COEFF_SHIFT = 2;
constexpr int32_t DM3[5*MAX_NUM_FILTER_STAGES] = {
536870912, 988616936, 455608573, 834606945, -482959709,
536870912, 1031466345, 498793368, 965834205, -467402235,
536870912, 1105821939, 573646688, 928470657, -448083489,
2339, 5093, 2776, 302068995, 4412722
};
// Blackaddr WARM Filter
// Butterworth, 8th order, cutoff = 2000 Hz
// Matlab/Octave command: [bz, az] = butter(8, 2000/44100/2);
// b(z) = 1.0e-05 * (0.0086 0.0689 0.2411 0.4821 0.6027 0.4821 0.2411 0.0689 0.0086_
// a(z) = 1.0000 -6.5399 18.8246 -31.1340 32.3473 -21.6114 9.0643 -2.1815 0.2306
constexpr unsigned WARM_NUM_STAGES = 4;
constexpr unsigned WARM_COEFF_SHIFT = 2;
constexpr int32_t WARM[5*MAX_NUM_FILTER_STAGES] = {
536870912,1060309346,523602393,976869875,-481046241,
536870912,1073413910,536711084,891250612,-391829326,
536870912,1087173998,550475248,835222426,-333446881,
46,92,46,807741349,-304811072
};
// Blackaddr DARK Filter
// Chebychev Type II, 8th order, stopband = 60db, cutoff = 1000 Hz
// Matlab command: [bz, az] = cheby2(8, 60, 1000/44100/2);
// b(z) = 0.0009 -0.0066 0.0219 -0.0423 0.0522 -0.0423 0.0219 -0.0066 0.0009
// a(z) = 1.0000 -7.4618 24.3762 -45.5356 53.1991 -39.8032 18.6245 -4.9829 0.5836
constexpr unsigned DARK_NUM_STAGES = 4;
constexpr unsigned DARK_COEFF_SHIFT = 1;
constexpr int32_t DARK[5*MAX_NUM_FILTER_STAGES] = {
1073741824,-2124867808,1073741824,2107780229,-1043948409,
1073741824,-2116080466,1073741824,2042553796,-979786242,
1073741824,-2077777790,1073741824,1964779896,-904264933,
957356,-1462833,957356,1896884898,-838694612
};
};
Write Preview
Loading…
Cancel
Save