QCameraViewFinder freezes and QCameraImageCapture stops saving

JRohner

Hi!

I have a QCameraViewFinder and a QCameraImageCapture. Somewhat randomly the viewfinder just freezes and stops showing a moving image. When this happens QCameraImageCapture also stops saving images to disk.

Strangely, QCamera also does not seem to fire any signals as my connected slots do nothing. Maybe I made an error? Here is my code (I'm on Qt 5.8.0 and OSX Sierra). The main code is in
void MainWindow::on_pushButton_clicked()

Thanks in advance!

/JC

#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    camera = new QCamera(this);
    viewfinder = new QCameraViewfinder(this);
    camera->setViewfinder(viewfinder);
    imageCapture = new QCameraImageCapture(camera);

    connect(camera, SIGNAL(locked()), this, SLOT(my_camera_lock()));
    connect(camera, SIGNAL(lockFailed()), this, SLOT(my_lock_failed()));

    ui->verticalLayout->addWidget(viewfinder);
    viewfinder->show();
    camera->start();

}

void MainWindow::on_pushButton_clicked()
{

    for(int i = 0; i < 40; i++){

        QString path = "/Users/JCRohner/Junk/image" + QString::number(i) + ".jpg";

        QApplication::beep();
        camera->searchAndLock();
        while(!imageCapture->isReadyForCapture()){
            QApplication::processEvents(QEventLoop::AllEvents, 100);
        }
        imageCapture->capture(path);
        camera->unlock();
        delayForSecs(3);
    }

}

void MainWindow::my_camera_lock(){
    qDebug()<<"locked";
}

void MainWindow::my_lock_failed(){
    qDebug()<<"lock failed";
}

void MainWindow::delayForSecs(int secs){
    QTime dieTime = QTime::currentTime().addSecs(secs);
    while (QTime::currentTime() < dieTime){
        QCoreApplication::processEvents(QEventLoop::AllEvents, 100);
    }
}


MainWindow::~MainWindow()
{
    delete ui;
}

jsulm

@JRohner Did you verify that connect() succeeded?

qDebug() << connect(camera, SIGNAL(locked()), this, SLOT(my_camera_lock()));
qDebug() << connect(camera, SIGNAL(lockFailed()), this, SLOT(my_lock_failed()));

Also the way your doing it is not really nice: you implement a blocking slot and use QApplication::processEvents to not to block the event loop. You should consider using QTimer.

JRohner

Thanks for your suggestions @jsulm ! I made the changes you proposed (see code below). The connections succeed as i get "true" and "true" using your code. My slots still do not get called however (nothing more than "true" and "true" gets outputted); and saving images drops out randomly (e.g. the first time i run the app i get all 41 images on disk; the second time i get 3-4 on disk, etc). Strange. I appreciate any suggestions!

#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    camera = new QCamera(this);
    viewfinder = new QCameraViewfinder(this);
    camera->setViewfinder(viewfinder);
    imageCapture = new QCameraImageCapture(camera);

    connect(camera, SIGNAL(locked()), this, SLOT(my_camera_lock()));
    connect(camera, SIGNAL(lockFailed()), this, SLOT(my_lock_failed()));
    qDebug() << connect(camera, SIGNAL(locked()), this, SLOT(my_camera_lock()));
    qDebug() << connect(camera, SIGNAL(lockFailed()), this, SLOT(my_lock_failed()));

    ui->verticalLayout->addWidget(viewfinder);
    viewfinder->show();
    camera->start();

    counter = 0;
    myTimer = new QTimer(this);
    connect(myTimer, SIGNAL(timeout()), this, SLOT(doCapture()));
    myTimer->start(4000);

}

void MainWindow::doCapture()
{

    QString path = "/Users/JCRohner/Junk/image" + QString::number(counter) + ".jpg";
    QApplication::beep();
    camera->searchAndLock();
    imageCapture->capture(path);
    camera->unlock();
    counter++;
    if(counter == 40) myTimer->stop();

}

void MainWindow::my_camera_lock(){
    qDebug()<<"locked";
}

void MainWindow::my_lock_failed(){
    qDebug()<<"lock failed";
}

MainWindow::~MainWindow()
{
    delete ui;
}

jsulm

@JRohner You need to somehow find out where it actually freezes. You can add some qDebug() << "..." debug output for that.