You signed in with another tab or window. Reload to refresh your session.You signed out in another tab or window. Reload to refresh your session.You switched accounts on another tab or window. Reload to refresh your session.Dismiss alert
* A wrap-up to swap between different oscillators seemlessly, allowing to produce non-aliased sounds by automatically switching between oscillators.
5
+
*
6
+
* This file is part of Mozzi.
7
+
*/
8
+
9
+
#ifndef META_OSCIL_H
10
+
#defineMETA_OSCIL_H
11
+
12
+
13
+
#if ARDUINO >= 100
14
+
#include"Arduino.h"
15
+
#else
16
+
#include"WProgram.h"
17
+
#endif
18
+
19
+
#include"Oscil.h"
20
+
#include"mozzi_fixmath.h"
21
+
22
+
23
+
/**
24
+
MetaOscil is a wrapper for several Oscil. Once constructed it will behave exactly as an Oscil except that it will automatically switch between Oscil depending on the asked frequency. This allows to produce non-aliased sounds by switching between tables with less and less harmonics as the frequency increases.
Declare a MetaOscil containing any number of Oscil pointers. Every Oscil should have the same TABLE_NUM_CELLS and UPDATE_RATE which are also passed in the MetaOscil constructor.
35
+
@param N_OSCIL is the number of Oscil contained in the MetaOscil. This cannot be changed after construction. */
@param cutoff_freq is the cutoff frequency of this Oscil
44
+
void addOscil(Oscil<NUM_TABLE_CELLS, UPDATE_RATE>* osc, int cutoff_freq)
45
+
{
46
+
oscillators[current_rank] = osc;
47
+
cutoff_freqs[current_rank] = cutoff_freq;
48
+
if (current_rank == 0) current_osc=oscillators[0];
49
+
current_rank += 1;
50
+
}*/
51
+
52
+
53
+
/** Set all Oscil of a MetaOscil.
54
+
@param first... is a list of pointers towards several Oscil */
55
+
template<typename ... T > voidsetOscils(Oscil<NUM_TABLE_CELLS, UPDATE_RATE>* first,T... elements)
56
+
{
57
+
oscillators[current_rank]=first;
58
+
if (current_rank == 0) current_osc=oscillators[0];
59
+
current_rank+=1;
60
+
setOscils(elements...);
61
+
current_rank = 0;
62
+
}
63
+
64
+
voidsetOscils(){};
65
+
66
+
67
+
/** Set all the cutoff frequencies for changing between Oscil. They have to be sorted in increasing values and contain at least N_OSCIL-1 values. Note that the last Oscil will be used by default for frequencies higher than the higher cutoff, hence the last value can be discarded.
68
+
@param first, elements... a set of int cutoff frequencies.*/
69
+
template<typename ... T > voidsetCutoffFreqs(int first,T... elements)
70
+
{
71
+
cutoff_freqs[current_rank]=first;
72
+
current_rank+=1;
73
+
setCutoffFreqs(elements...);
74
+
current_rank = 0;
75
+
}
76
+
77
+
voidsetCutoffFreqs() {};
78
+
79
+
/** Set or change the cutoff frequency of one Oscil.
80
+
@param rank is the rank of the Oscil.
81
+
@param freq is the cutoff frequency. */
82
+
voidsetCutoffFreq(int freq, byte rank)
83
+
{
84
+
cutoff_freqs[rank] = freq;
85
+
}
86
+
87
+
/** Updates the phase according to the current frequency and returns the sample at the new phase position.
88
+
@return the next sample.
89
+
*/
90
+
inline
91
+
int8_tnext() {return current_osc->next();}
92
+
93
+
/** Change the sound table which will be played by the Oscil of rank.
94
+
@param TABLE_NAME is the name of the array in the table ".h" file you're using.
/* Example using a MetaOscil to generate an alias free square wave on a sweep
2
+
using Mozzi sonification library.
3
+
4
+
Waveforms which are not only sines (Saw, square, triangle) are composed by a lot of harmonics which are at frequencies multiple of the fundamental frequency.
5
+
If the frequency of one of these harmonics is higher than half the sampling frequency (https://en.wikipedia.org/wiki/Nyquist_frequency) (AUDIO_RATE/2 here)
6
+
it will create "aliases" (https://en.wikipedia.org/wiki/Aliasing) which will sound out of tune are they not harmonically related to the fundamental.
7
+
The higher the pitch, the more harmonics are above the Nyquist limit and the more aliased will be present for a given waveform.
8
+
9
+
One way to avoid aliases is to use "band-limited" waveforms which have a limited sets of harmonics in order to avoid them to reach the Nyquist limit.
10
+
As these waveforms are band-limited they will sound less "crunchy" if they are used at frequencies lower than what they are meant to be because they
11
+
lack the high frequency contents.
12
+
13
+
In order to paliate that, a common technique is to "swap" wave tables on the fly in order to keep the frequency content up to the Nyquist frequency but
14
+
not above. This is the principal usage of MetaOscil.
15
+
16
+
MetaOscil can be used (after construction) as a proper Oscil but really is a bunch of oscillators with only one playing.
17
+
It will switch between different oscils seemlessly depending on the asked frequency. This allows to switch between oscillators with less
18
+
and less harmonics as the pitch goes up, in order to avoid aliases, which is demonstrated by this example.
19
+
20
+
The bandlimited tables are nammed according to the max frequency they can play without bringing aliases at a given frequency. For example:
21
+
square_max_90_at_16384_512_int8.h ensures that no aliases will be present up to 90Hz at 16384Hz sampling rate (the default for Arduino).
22
+
If your sampling rate is higher (say 32768 which is the default for most 32bits platforms) this table will be able to play up to
23
+
180=90*2Hz without aliases, as the Nyquist frequency is two times higher.
24
+
25
+
Circuit: Audio output on digital pin 9 on a Uno or similar, or
26
+
DAC/A14 on Teensy 3.1, or
27
+
check the README or http://sensorium.github.com/Mozzi/
// All the tables used for the MetaOscil need to be included
43
+
#include<tables/BandLimited_SQUARE/512/square_max_90_at_16384_512_int8.h>// band limited table that guarantee no alias up to a frequency of 90Hz at a sampling frequency of 16384 (or 180Hz at a sampling frequency of 32768Hz)
44
+
#include<tables/BandLimited_SQUARE/512/square_max_101_at_16384_512_int8.h>// band limited table that guarantee no alias up to a frequency of 101Hz at a sampling frequency of 16384
45
+
#include<tables/BandLimited_SQUARE/512/square_max_122_at_16384_512_int8.h>// band limited table that guarantee no alias up to a frequency of 122Hz at a sampling frequency of 16384
46
+
#include<tables/BandLimited_SQUARE/512/square_max_138_at_16384_512_int8.h>// band limited table that guarantee no alias up to a frequency of 138Hz at a sampling frequency of 16384
47
+
#include<tables/BandLimited_SQUARE/512/square_max_154_at_16384_512_int8.h>// band limited table that guarantee no alias up to a frequency of 154Hz at a sampling frequency of 16384
48
+
#include<tables/BandLimited_SQUARE/512/square_max_174_at_16384_512_int8.h>// band limited table that guarantee no alias up to a frequency of 174Hz at a sampling frequency of 16384
49
+
#include<tables/BandLimited_SQUARE/512/square_max_210_at_16384_512_int8.h>// band limited table that guarantee no alias up to a frequency of 210Hz at a sampling frequency of 16384
50
+
#include<tables/BandLimited_SQUARE/512/square_max_264_at_16384_512_int8.h>// band limited table that guarantee no alias up to a frequency of 264Hz at a sampling frequency of 16384
51
+
#include<tables/BandLimited_SQUARE/512/square_max_327_at_16384_512_int8.h>// band limited table that guarantee no alias up to a frequency of 327Hz at a sampling frequency of 16384
52
+
#include<tables/BandLimited_SQUARE/512/square_max_431_at_16384_512_int8.h>// band limited table that guarantee no alias up to a frequency of 431Hz at a sampling frequency of 16384
53
+
#include<tables/BandLimited_SQUARE/512/square_max_546_at_16384_512_int8.h>// band limited table that guarantee no alias up to a frequency of 546Hz at a sampling frequency of 16384
54
+
#include<tables/BandLimited_SQUARE/512/square_max_744_at_16384_512_int8.h>// band limited table that guarantee no alias up to a frequency of 744Hz at a sampling frequency of 16384
55
+
#include<tables/BandLimited_SQUARE/512/square_max_910_at_16384_512_int8.h>// band limited table that guarantee no alias up to a frequency of 910Hz at a sampling frequency of 16384
56
+
#include<tables/BandLimited_SQUARE/512/square_max_1170_at_16384_512_int8.h>// band limited table that guarantee no alias up to a frequency of 1170Hz at a sampling frequency of 16384
57
+
#include<tables/BandLimited_SQUARE/512/square_max_1638_at_16384_512_int8.h>// band limited table that guarantee no alias up to a frequency of 1638Hz at a sampling frequency of 16384
58
+
#include<tables/BandLimited_SQUARE/512/square_max_2730_at_16384_512_int8.h>// band limited table that guarantee no alias up to a frequency of 2730Hz at a sampling frequency of 16384
59
+
#include<tables/BandLimited_SQUARE/512/square_max_8192_at_16384_512_int8.h>// band limited table that guarantee no alias up to a frequency of 8192Hz at a sampling frequency of 16384 (this is basically a sine wave)
60
+
61
+
// The proper Oscillators that will be managed by the MetaOscil
62
+
// use: Oscil <table_size, update_rate> oscilName (wavetable), look in .h file of table #included above
// use: MetaOscil <table_size, update_rate, number_of_oscil> MetaoscilName. All oscils used should have the same table_size and **have to be put in increasing order of cutoff_frequencies**.
#defineCONTROL_RATE256// Hz, powers of 2 are most reliable
87
+
88
+
int freq = 10;
89
+
90
+
91
+
voidsetup() {
92
+
// Set the cutoff frequencies for all the Oscil in the MetaOscil ie at which frequency the MetaOscil will switch to the next Oscillator. Note that these are the same frequencies than the tables names in this case.
93
+
// This have to follow the order given at the MetaOscil creation: this needs to be in increasing order.
0 commit comments