将OpenGL与RtAudio (或端口音频)同步

Question

我需要用Metronome与OpenGL同步一些绘图。Metronome是用libPD构建的，使用RtAudio来玩。这两件事都很好(分别)，但是我需要用节拍器来移动一个物体(三角形)。应用程序也必须播放单击。这两个动作都必须并行进行(播放和绘图)。我也应该加一张midi唱片。我的申请是在C++里。我试着用一个线程来运行它，但是它不起作用。我试图遵循这样的解释：How to make my metronome play at the same time as recording in my program? -- gui是WxWidgets。线程以这种方式使用Poco::Runnable完成：

class MyThread : public Poco::Runnable {
public:
    MyThread(BasicGLPane *pane, std::shared_ptr<SoundManager> man);

    virtual void run();
private:
    BasicGLPane *_pane;
    std::shared_ptr<SoundManager> _man;
};

MyThread::MyThread(BasicGLPane *pane, std::shared_ptr<SoundManager> man) {
    _pane = pane;
    _man = man;
}


void MyThread::run() {
    _man->play();
    _pane->startAnimation();    
}

BasicGLpane是wxGLCanvas。声音管理器类的THe播放功能如下：

void SoundManager::play() {
    // Init pd
    if(!lpd->init(0, 2, sampleRate)) {
        std::cerr << "Could not init pd" << std::endl;
        exit(1);
    }    
    // Receive messages from pd
    lpd->setReceiver(object.get());
    lpd->subscribe("metro-bang");
    lpd->subscribe("switch");

    // send DSP 1 message to pd
    lpd->computeAudio(true);

    // load the patch
    open_patch("metro-main.pd");
    std::cout << patch << std::endl;    

    // Use the RtAudio API to connect to the default audio device.
    if(audio->getDeviceCount()==0){
        std::cout << "There are no available sound devices." << std::endl;
        exit(1);
    }

    RtAudio::StreamParameters parameters;
    parameters.deviceId = audio->getDefaultOutputDevice();
    parameters.nChannels = 2;

    RtAudio::StreamOptions options;
    options.streamName = "Pd Metronome";
    options.flags = RTAUDIO_SCHEDULE_REALTIME;
    if ( audio->getCurrentApi() != RtAudio::MACOSX_CORE ) {
        options.flags |= RTAUDIO_MINIMIZE_LATENCY; // CoreAudio doesn't seem to like this
    }
    try {
        if(audio->isStreamOpen()) {
            audio->closeStream();
        }
        else {
            audio->openStream( &parameters, NULL, RTAUDIO_FLOAT32, sampleRate, &bufferFrames, &audioCallback, lpd.get(), &options );
            audio->startStream();
        }
    }
    catch ( RtAudioError& e ) {
        std::cerr << e.getMessage() << std::endl;
        exit(1);
    }  
}

OpenGL绘图方法如下：

void BasicGLPane::startAnimation() {
    std::cout<<"Start Animation"<<std::endl;
    triangle_1(p1, p2, p3);    
    Refresh();
}

void BasicGLPane::triangle_1(std::shared_ptr<vertex2f> _p1, std::shared_ptr<vertex2f> _p2, std::shared_ptr<vertex2f> _p3) {
    CGLContextObj ctx = CGLGetCurrentContext(); //enable multithreading (only apple) 
    CGLError err = CGLEnable( ctx, kCGLCEMPEngine);
    if (err != kCGLNoError ) {
        glEnable(GL_MULTISAMPLE);
        glMatrixMode(GL_PROJECTION);
        glLoadIdentity();
        glOrtho(0, getWidth(), getHeight(),0 , -1, 1);
        glShadeModel(GL_SMOOTH);
        glBegin(GL_POLYGON);                      // Drawing Using Triangles
        glColor3f (157.0/255.0, 44.0/255.0, 44.0/255.0);
        glVertex3f( p1->x, p1->y, 0.0f);              // Top left
        glVertex3f(p2->x,p2->y, 0.0f);              // Top Right
        glVertex3f( p3->x,p3->y, 0.0f);               //Bottom
        glEnd();
        glMatrixMode(GL_MODELVIEW);
        glEnable (GL_BLEND);
        glLoadIdentity();
        glDisable(GL_MULTISAMPLE);
    }
}

线程使用以下函数调用：

void BasicGLPane::startThread() {
    while (_object->getCounter()<10) { //this is only to test the functionality
        thread.start(work);
    }
    thread.join();
    manager->stop();
}

在此之后，这个功能在Reder中被称为：

void BasicGLPane::render( wxPaintEvent& evt ) {
    //some code here, not important....
    startThread();
    SwapBuffers();
}

也许我要改变这个对象，这并不重要，我的问题是同步。我认为RtAudio正在制造问题，因为我变成了EXC_BAD_Acces to getDeviceCount()或RtAudio的任何其他函数。仅在线程上下文中出现。用港口音频更好吗？很高兴知道我做错了什么，或者有别的办法解决这个问题

Answer 1

我找到了解决办法。问题在于wxwidget主循环与openGL.The解决方案之间的交互是以以下方式创建一个空闲事件：

//on wxApp
void MyApp::activateRenderLoop(bool on) {
    if(on && !render_loop_on) {
        Connect(wxID_ANY, wxEVT_IDLE, wxIdleEventHandler(MyApp::onIdle));
        render_loop_on = true;
    }
    else if (!on && render_loop_on) {
        Disconnect(wxEVT_IDLE, wxIdleEventHandler(MyApp::onIdle));
        render_loop_on = false;
    }
}

void MyApp::onIdle(wxIdleEvent &evt) {
    activateRenderLoop(glPane->render_on);
    if(render_loop_on) {
        std::cout<<"MyApp on Idle, render_loop_on"<<std::endl;
        glPane->paint_now();
        evt.RequestMore();
    }
}

//on event table:
EVT_PAINT(BasicGLPane::paint_rt)

void BasicGLPane::rightClick(wxMouseEvent& event) {
    render_on = true;
    manager->init();
    SLEEP(2000);
    manager->play();
    wxGetApp().activateRenderLoop(true);   
}

void BasicGLPane::paint_rt(wxPaintEvent &evt) {
    wxPaintDC dc(this);
    render_rt(dc);
}

void BasicGLPane::paint_now(){
    wxClientDC dc(this);
    std::cout<<"paint now() "<<std::endl;
    render_rt(dc);
}

void BasicGLPane::render_rt(wxDC &dc) {
    wxGLCanvas::SetCurrent(*m_context);
    if(_object->getCounter()>=10) {
        wxGetApp().activateRenderLoop(false);
        manager->stop();
        render_on = false;
    }
    else {
        ctx = CGLGetCurrentContext(); //OSx only
        err =  CGLEnable( ctx, kCGLCEMPEngine); //OSX only
        std::cout<<"render_rt CGLError: "<<err<<std::endl;
        if (err==0) {
            glTranslatef(p3->x, p3->y, 0);
            Refresh(false);
        }

    }
}

同步器现在工作得很好。