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| /* description: 波形情報をメモリではなく全て演算ベースにする新音源用のメモ */ | |
| /* とりあえず、サイン波、矩形波、ノコギリ波のみ */ | |
| /* ノイズ発生装置は後回し */ | |
| #include <math.h> | |
| #define PI 3.1415926535897932 | |
| #define PI2 6.2831853071795864 | |
| double calcwav_sin(double r) | |
| { | |
| return sin(r); | |
| } | |
| double calcwav_square(double r) | |
| { | |
| r=fmod(r,PI2); | |
| if(r<0.0) r+=PI2; | |
| if(r<PI) return 1.0; | |
| return -1.0; | |
| } | |
| double calcwav_pulse(double r) | |
| { | |
| r=fmod(r,PI2); | |
| if(r<0.0) r+=PI2; | |
| r/=PI; | |
| r-=1.0; | |
| return r; | |
| } |
上記はその新音源の波形生成ルーチンです。
波形データをメモリに持つ仕組みではなく、関数で求める形。
サイン波、矩形波、ノコギリ波の３つ。
2πで1Hzということになります。
【音程算出】
サンプリング周波数44100Hzで音程周波数440Hz（ラ）を出す場合、
2π ÷ （44100 ÷ 440）
で、radの増分が求まるという感じです。
だいたい0.063ぐらいかな。
（そして、radのカーソルをチャネル毎に持たせる）
それを毎回計算すると処理性能が悪くなってしまうので、音程ごとの増分値をテーブルに持たせれば、性能的に良い感じになる筈です。
テーブルに持たせる増分値を求めるプログラムを作成。
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| /* 88鍵ピアノの音階周波数 & サンプリング周波数1Hzあたりのラジアン増分を求めて表示 */ | |
| #include <stdio.h> | |
| #define S 44100.00 | |
| #define B 1.0594631 | |
| #define PI 3.1415926535897932 | |
| #define PI2 6.2831853071795864 | |
| int main(int argc,char* argv[]) | |
| { | |
| const char* t[12]={ | |
| "A " | |
| ,"A#" | |
| ,"B " | |
| ,"C " | |
| ,"C#" | |
| ,"D " | |
| ,"D#" | |
| ,"E " | |
| ,"F " | |
| ,"F#" | |
| ,"G " | |
| ,"G#" | |
| }; | |
| double hz[88]; | |
| int n=0; | |
| double a=13.75; | |
| double b; | |
| for(n=0;n<88;n++) { | |
| if(n%12==0) { | |
| a*=2.0; | |
| hz[n]=a; | |
| } else { | |
| hz[n] = hz[n-1] * B; | |
| } | |
| b=PI2/(S/hz[n]); | |
| printf("%s : %9.4fHz : %.4f rad/1Hz\n",t[n%12],hz[n],b); | |
| } | |
| return 0; | |
| } |
上記プログラムで求めたテーブルは↓のような感じ
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| double ARTBL[88] = { | |
| 0.0039180860759056 | |
| ,0.0041510676200458 | |
| ,0.0043979029690434 | |
| ,0.0046594159130819 | |
| ,0.0049364792274631 | |
| ,0.0052300175854136 | |
| ,0.0055410106440968 | |
| ,0.0058704963141278 | |
| ,0.0062195742235045 | |
| ,0.0065894093875141 | |
| ,0.0069812360968648 | |
| ,0.0073963620370163 | |
| ,0.0078361721518113 | |
| ,0.0083021352400916 | |
| ,0.0087958059380867 | |
| ,0.0093188318261638 | |
| ,0.0098729584549261 | |
| ,0.0104600351708273 | |
| ,0.0110820212881937 | |
| ,0.0117409926282557 | |
| ,0.0124391484470089 | |
| ,0.0131788187750282 | |
| ,0.0139624721937296 | |
| ,0.0147927240740326 | |
| ,0.0156723443036225 | |
| ,0.0166042704801833 | |
| ,0.0175916118761735 | |
| ,0.0186376636523276 | |
| ,0.0197459169098523 | |
| ,0.0209200703416545 | |
| ,0.0221640425763874 | |
| ,0.0234819852565114 | |
| ,0.0248782968940178 | |
| ,0.0263576375500565 | |
| ,0.0279249443874593 | |
| ,0.0295854481480652 | |
| ,0.0313446886072451 | |
| ,0.0332085409603666 | |
| ,0.0351832237523470 | |
| ,0.0372753273046551 | |
| ,0.0394918338197046 | |
| ,0.0418401406833091 | |
| ,0.0443280851527748 | |
| ,0.0469639705130227 | |
| ,0.0497565937880356 | |
| ,0.0527152751001130 | |
| ,0.0558498887749185 | |
| ,0.0591708962961304 | |
| ,0.0626893772144902 | |
| ,0.0664170819207332 | |
| ,0.0703664475046939 | |
| ,0.0745506546093103 | |
| ,0.0789836676394092 | |
| ,0.0836802813666181 | |
| ,0.0886561703055495 | |
| ,0.0939279410260454 | |
| ,0.0995131875760713 | |
| ,0.1054305502002260 | |
| ,0.1116997775498371 | |
| ,0.1183417925922608 | |
| ,0.1253787544289804 | |
| ,0.1328341638414663 | |
| ,0.1407328950093879 | |
| ,0.1491013092186206 | |
| ,0.1579673352788184 | |
| ,0.1673605627332363 | |
| ,0.1773123406110990 | |
| ,0.1878558820520909 | |
| ,0.1990263751521426 | |
| ,0.2108611004004520 | |
| ,0.2233995550996741 | |
| ,0.2366835851845215 | |
| ,0.2507575088579608 | |
| ,0.2656683276829326 | |
| ,0.2814657900187757 | |
| ,0.2982026184372412 | |
| ,0.3159346705576367 | |
| ,0.3347211254664726 | |
| ,0.3546246812221980 | |
| ,0.3757117641041818 | |
| ,0.3980527503042852 | |
| ,0.4217222008009040 | |
| ,0.4467991101993482 | |
| ,0.4733671703690431 | |
| ,0.5015150177159216 | |
| ,0.5313366553658653 | |
| ,0.5629315800375514 | |
| ,0.5964052368744823 | |
| }; |
【波形合成】
基本波形をベースに合成波形も出力できるようにすれば、出力できる音色数は7種類。
- sin
- square
- pulse
- sin + square
- sin + pulse
- square + pulse
- sin + square + pulse
あとはノイズ1種類 + 7種それぞれとノイズの合成で15種類
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