raspi-synth/main.cpp

#include <cstdlib>
#include <cmath>
#include <iostream>

#include "portaudio.h"

#include "oscillator.h"
#include "svf.h"

using namespace std;

#define SAMPLE_RATE 48000

typedef struct {
    Oscillator oscs[8];
    SVFx2 filter;
    float time;
} State;

static int audioCallback(
        const void *inputBuffer,
        void *outputBuffer,
        unsigned long framesPerBuffer,
        const PaStreamCallbackTimeInfo* timeInfo,
        PaStreamCallbackFlags statusFlags,
        void *userData ) {
    
    State *state = (State*) userData;
    float *out = (float*)outputBuffer;

    for(int i = 0; i < framesPerBuffer; i++) {
        float value = 0;
        for(int j = 0; j < 8; ++j) {
            value += state->oscs[j].tick();
        }
        value *= 0.125;
        value *= 0.5;
        state->filter.setFrequency(0.21 + 0.20 * sin(M_PI * state->time));
        value = state->filter.tick(value);
        *out++ = value;
        *out++ = value;
        state->time += 1.0 / SAMPLE_RATE;

    }
    return 0;
}

void handlePAError(PaError err) {
    Pa_Terminate();
    cerr << "PortAudio error" << endl;
    cerr << "Error number: " << err << endl;
    cerr << "Error message: " << Pa_GetErrorText(err) << endl;
    exit(err);
}

static State state;
int main(void) {
    for(int i = 0; i < 8; ++i) {
        float freq = 440 + i;
        state.oscs[i].phaseStep = (freq * 2 * M_PI) / SAMPLE_RATE;
        state.oscs[i].phase = PIx2 * (float) rand() / RAND_MAX;
    }
    state.filter.setMode(SVFx2::MODE_LP);
    state.filter.setQ(1);
    state.time = 0;
    
    PaStream *stream;
    PaError err;

    err = Pa_Initialize();
    if(err != paNoError) {
        handlePAError(err);
    }

    PaHostApiIndex deviceCount = Pa_GetDeviceCount();
    cout << "Select audio output device:" << endl;
    for(int i = 0; i < deviceCount; ++i) {
        const PaDeviceInfo* deviceInfo = Pa_GetDeviceInfo(i);
        if(deviceInfo->maxOutputChannels < 2) {
            continue;
        }
        cout << i << ". " << deviceInfo->name << " (" << Pa_GetHostApiInfo(deviceInfo->hostApi)->name << ")" << endl;
    }
    string input;
    PaHostApiIndex deviceIndex;
    for(;;) {
        getline(cin, input);
        try {
            deviceIndex = stoi(input);
            if(deviceIndex >= 0 && deviceIndex < deviceCount) {
                break;
            }
        } catch(...) { }
        cout << "Invalid selection" << endl;   
    }

    /* Open an audio I/O stream. */
    PaStreamParameters streamParams;
    streamParams.device = deviceIndex;
    streamParams.channelCount = 2;
    streamParams.sampleFormat = paFloat32;
    streamParams.suggestedLatency = 0;
    streamParams.hostApiSpecificStreamInfo = NULL;
    err = Pa_OpenStream(
        &stream,
        NULL,           /* no input channels */
        &streamParams,  /* stereo output */
        SAMPLE_RATE,
        0,            /* frames per buffer */
        paNoFlag,
        audioCallback,
        &state);
    if(err != paNoError) {
        handlePAError(err);
    }

    err = Pa_StartStream(stream);
    if(err != paNoError) { 
        handlePAError(err);
    }

    const PaStreamInfo *streamInfo = Pa_GetStreamInfo(stream);
    cout << "Latency: " << round(1000 * streamInfo->outputLatency) << " ms" << endl;

    /* Wait for Return key */
    getchar();

    err = Pa_StopStream(stream);
    if(err != paNoError) {
        handlePAError(err);
    }
    err = Pa_CloseStream(stream);
    if(err != paNoError) {
        handlePAError(err);
    }
    Pa_Terminate();
    cout << "Terminating" << endl;
    
    return err;
}