wavetable.cpp

#include "wavetable.h"
#include <stdio.h>
#include "soundprocessor.h"
#include <cmath>

#define EPSILON 0.001

using namespace std;

WaveTable::WaveTable() {
    buildSawtooth();
    buildSquare();
    buildTriangle();
}

WaveTable::~WaveTable() {
    int i;
    for(i = 0; i < NUM_NOTES; i++) {
        delete[] triangleTable[i];
        delete[] sawtoothTable[i];
        delete[] squareTable[i];
    }
}

double WaveTable::triangle(double phase, double freq) {
    if(freq < ALIASING_THRESHOLD) {
        double t = phase*freq/SAMPLE_RATE;
        return pow(-1, (int)floor(t+0.5))*((t*2)-1);
    }
    return getSample(phase, freq, triangleTable);
} 
double WaveTable::square(double phase, double freq) {
    if(freq < ALIASING_THRESHOLD) {
        return (phase*freq/SAMPLE_RATE) < 0.5 ? 0 : 1;
    }
    return getSample(phase, freq, squareTable);
}

double WaveTable::sawtooth(double phase, double freq) {
    if(freq < ALIASING_THRESHOLD) {
        double t = phase*freq/SAMPLE_RATE;
        return (t - floor(t+0.5))*2;
    }
    else
        return getSample(phase, freq, sawtoothTable);
}

double WaveTable::getSample(double phase, double freq, double **table) {
    double closestFreq, ratio, sample, cursor, period, amountRead, amountLeft;
    int closest, index;
    sample = 0;
    freq = roundf(freq * 100.0f) / 100.0f;
    closest = (int)floor(12*(log(freq)/440)/log(2))+MIDDLE_A_INDEX;
    closest = closest >= NUM_NOTES ? NUM_NOTES - 1 : (closest < 0 ? 0 : closest);
    closestFreq = 440 * pow(2,(double(closest-MIDDLE_A_INDEX))/12);
    period = SAMPLE_RATE/closestFreq;
    if (fabs((closestFreq - freq)/closestFreq) < EPSILON) {
        ratio = 1;
    }
    else
        ratio = freq/closestFreq;
    amountRead = 0;
    cursor = ratio*phase;
    while(fabs((amountRead-ratio))/ratio > EPSILON && amountRead < ratio) {
        cursor = fmod(cursor, period);
        amountLeft = min(min(1.0, ratio-amountRead), min(ratio-amountRead, min(period-cursor, (fabs((fmod(cursor, 1)) < EPSILON)?cursor+1:ceil(cursor))-cursor)));
        index = (int)floor(cursor);
        amountRead += amountLeft;
        cursor += amountLeft;
        sample += amountLeft*table[closest][index];
    }
    return sample/ratio;
}

double WaveTable::sine(double phase, double freq) {
    return sin(((phase*freq)/SAMPLE_RATE)*2*PI);
}

void WaveTable::buildTriangle() {
    int i, j;   
    double freq, period;
    for(i = 0; i < NUM_NOTES; i++) {
        freq = 440 * pow(2,(double(i-MIDDLE_A_INDEX))/12); // sawtoothTable[MIDDLE_A_INDEX] = A440
        period = SAMPLE_RATE/freq;
        triangleTable[i] = new double[(int)ceil(period)];
        for(j = 0; j < ceil(period); j++) {
            triangleTable[i][j] = triangleFunction(j, freq);
        }
    }
}

void WaveTable::buildSquare() {
    int i, j;   
    double freq, period;
    for(i = 0; i < NUM_NOTES; i++) {
        freq = 440 * pow(2,(double(i-MIDDLE_A_INDEX))/12); // sawtoothTable[MIDDLE_A_INDEX] = A440
        period = SAMPLE_RATE/freq;
        squareTable[i] = new double[(int)ceil(period)];
        for(j = 0; j < ceil(period); j++) {
            squareTable[i][j] = squareFunction(j, freq);
        }
    }
}

void WaveTable::buildSawtooth() {
    int i, j;   
    double freq, period;
    for(i = 0; i < NUM_NOTES; i++) {
        freq = 440 * pow(2,(double(i-MIDDLE_A_INDEX))/12); // sawtoothTable[MIDDLE_A_INDEX] = A440
        period = SAMPLE_RATE/freq;
        sawtoothTable[i] = new double[(int)ceil(period)];
        for(j = 0; j < (int)ceil(period); j++) {
            sawtoothTable[i][j] = sawtoothFunction(j, freq);
        }
    }
}

double WaveTable::sawtoothFunction(double phase, double f) {
    double t, sum, sample;
    int i;
    t = phase/SAMPLE_RATE;
    sum = 0;
    for(i = 1; i < SAMPLE_RATE/(2*f); i++) {
        sum += pow(-1, i+1)*sin(2*PI*i*f*t)/i;
    }
    sample = (2*sum)/(PI);
    return sample;
}

double WaveTable::squareFunction(double phase, double f) {
    double t, sum, sample;
    int i;
    t = phase/SAMPLE_RATE;
    sum = 0;
    for(i = 1; i < (SAMPLE_RATE/4)/f; i++) {
        sum += sin(2*PI*(2*i-1)*f*t)/(2*i-1);
    }
    sample = (4*sum)/PI;
    return sample;
}

double WaveTable::triangleFunction(double phase, double f) {
    double t, sum, sample;
    int i;
    t = phase/SAMPLE_RATE;
    sum = 0;
    for(i = 0; i < (SAMPLE_RATE/4)/f; i++) {
        sum += pow(-1, i)*sin((2*i+1)*2*PI*f*t)/pow(2*i+1, 2);
    }
    sample = (8*sum)/(pow(PI, 2));
    return sample;
}