ジェネレーター5

　複数の周波数が混在した信号を利用する時にはフィルタで分離する必要があります。そのフィルタを評価するために指定範囲の周波数をスイープするジェネレーターを作りました。

#include <iostream>
#include <windows.h>
#include <math.h>
#include <MMSystem.h>

#pragma comment (lib, "winmm.lib")

void createWave(LPWORD lpData, size_t frequency, size_t sampling, WORD amplitude) {
    size_t wavelength = sampling / frequency;
    double d = 360.0 / wavelength;
    double pi = 3.14159265359;
    for (int i = 0; i < wavelength; i++) {
        lpData[i] = (WORD)(amplitude * sin(d * (i % wavelength) / 180.0 * pi));
    }
}

int main() {

    WAVEFORMATEX wfe;
    static HWAVEOUT hWaveOut;
    static WAVEHDR whdr;
    static LPWORD lpWave;
    static LPWORD lpData;

    // 最初と最後の1sは出力しないので3以上とする
    size_t terms = 7;

    size_t i, j, start, end;
    size_t frequency = 400;
    size_t sampling = 384000;
    size_t wavelength = sampling / frequency;

    wavelength = sampling / frequency;
    wfe.wFormatTag = WAVE_FORMAT_PCM;
    wfe.nChannels = 2;
    wfe.wBitsPerSample = 16;
    wfe.nBlockAlign = wfe.nChannels * wfe.wBitsPerSample / 8;
    wfe.nSamplesPerSec = (DWORD)sampling;
    wfe.nAvgBytesPerSec = wfe.nSamplesPerSec * wfe.nBlockAlign;
    waveOutOpen(&hWaveOut, 0, &wfe, 0, 0, CALLBACK_NULL);
    lpWave = (LPWORD)calloc(sizeof(WORD), wfe.nChannels * sampling * terms);

    end = sampling * wfe.nChannels * 1;
    WORD amplitude = 32767;
    for (i = 0; i < end; i++) {
        lpWave[i] = 0;
    }

    // 最初の1sは出力しない
    start = sampling * wfe.nChannels * 1;
    end = wfe.nChannels * sampling * terms;
    // 最後の1sは出力しない
    end -= sampling * wfe.nChannels * 1;

    size_t valWavelength;
    size_t valFrequency;
    for (i = start, j = 0; i < end; i += 2) {
        if (j == 0) {
            valFrequency = frequency + ((i - start) * (20000.0- frequency)) / (sampling * wfe.nChannels * (terms - 2));
            valWavelength = sampling / valFrequency;
            lpData = (LPWORD)calloc(sizeof(WORD), valWavelength);
            createWave(lpData, valFrequency, sampling, amplitude);
        }
        lpWave[i] = lpData[j];
        ++j;
        if (j >= valWavelength) {
            j = 0;
            free(lpData);
        }
    }

    lpData = (LPWORD)calloc(sizeof(WORD), wavelength);
    createWave(lpData, frequency, sampling, amplitude);
    for (i = start+1, j = 0; i < end; i += 2) {
        lpWave[i] = lpData[j];
        ++j;
        if (j >= wavelength) { j = 0; }
    }
    free(lpData);

    whdr.lpData = (LPSTR)lpWave;
    whdr.dwBufferLength = wfe.nAvgBytesPerSec * terms;
    whdr.dwFlags = WHDR_BEGINLOOP | WHDR_ENDLOOP;
    whdr.dwLoops = 1;
    waveOutPrepareHeader(hWaveOut, &whdr, sizeof(WAVEHDR));
    waveOutWrite(hWaveOut, &whdr, sizeof(WAVEHDR));
    
    char str[128];
    std::cout << "hello, world\n";
    std::cin >> str;

}