Qt OpenCv "VIDIOC_QUERYCTRL: Input/output error" causing application shutdown - c++

Question

I am working on USB WebCamera using OpenCv in Qt.The code works fine for taking images, saving images etc. But randomly it generates error "VIDIOC_QUERYCTRL: Input/output error" causing my whole qt application to shutdown.
Actually The Scenario of my application is as follow:
In MainWindow.c, I have a pushbutton, which is when pressed starts the camera:
void MainWindow::on_pushButton_continue_pressed()
{
camcapture = new CamCapture( imgResolution, defaultPath, this);
connect(camcapture, SIGNAL(imgChange(QString)), this, SLOT(changeImg(QString)));
camcapture->show();
}
and Here is piece of my CamCapture Class:
CamCapture::CamCapture( int Resolution, QString path, QWidget *parent) :
QFrame(parent),
ui(new Ui::CamCapture), timer_(this), counter_(0)
{
ui->setupUi(this);
/*----some variable initialization---*/
camInit();
timer_.start(100);
connect(&timer_,SIGNAL(timeout()), this,SLOT(captureLoop()));
}
void CamCapture::camInit()
{
capture_ = cvCaptureFromCAM(0);
if (!capture_)
{
qDebug()<<"cannot get webcam...";
ui->label_image->setText("No webcam!");
ui->label_image->setAlignment(Qt::AlignCenter);
buttonActiveStatus( false, false, false );
return;
}
cvGrabFrame(capture_); // Grabs frame from camera or file
image_ = cvRetrieveFrame(capture_); // Gets the image grabbed with cvGrabFrame
qDebug() << "image size : " << image_->width << "x" << image_->height;
qDebug() << "\n" << ui->label_image->x();
qDebug() << "\n" << ui->label_image->y();
}
QImage CamCapture::Ipl2QImage(const IplImage *newImage)
{
QImage qtemp;
if (newImage && cvGetSize(newImage).width > 0)
{
int x;
int y;
char* data = newImage->imageData;
qtemp= QImage(newImage->width, newImage->height,QImage::Format_RGB32 );
for( y = 0; y < newImage->height; y++, data +=newImage->widthStep )
for( x = 0; x < newImage->width; x++)
{
uint *p = (uint*)qtemp.scanLine (y) + x;
*p = qRgb(data[x * newImage->nChannels+2],
data[x * newImage->nChannels+1],data[x * newImage- >nChannels]);
}
}
return qtemp;
}
void CamCapture::captureLoop()
{
if ( !capture_ )
{
return;
}
cvGrabFrame(capture_);
image_ = cvRetrieveFrame(capture_);
if (image_)
{
counter_ ++;
qImage_ = Ipl2QImage(image_);
ui->label_image- >setPixmap(QPixmap::fromImage(qImage_.scaled(width(),height()),Qt::AutoColor));
}
}
void CamCapture::on_pushButton_cancel_pressed()
{
cvReleaseCapture( &capture_ );
cvDestroyAllWindows();
delay(100);
qDebug() << "nb frames :" << counter_;
CamCapture::close();
}
void CamCapture::on_pushButton_capture_pressed()
{
savePath = _imgPath;
timer_.stop();
frame = cvQueryFrame(capture_); // Gets the image grabbed with cvGrabFrame
}
void CamCapture::on_pushButton_retake_pressed()
{
timer_.start(100);
captureLoop();
}
void CamCapture::on_pushButton_save_pressed()
{
int iwidth = _imgWidth * _imgResolution * scaledFactor;
int iheight = _imgHeight * _imgResolution * scaledFactor;
QString str = savePath;
IplImage *small;
small = cvCreateImage(cvSize(iwidth,iheight), 8, 3);
cvResize(frame, small);
cvSaveImage(savePath.toUtf8().constData(),small);
delay(100);
_imgNum++;
emit imgChange(savePath);
on_pushButton_cancel_pressed();
}
The above code randomly generates error ( causing my application shutdowm ) as follow:
Debugging starts
&"warning: GDB: Failed to set controlling terminal: Invalid argument\n"
Corrupt JPEG data: bad Huffman code
image size : 640 x 480
5
10
nb frames : 11
VIDIOC_QUERYCTRL: Input/output error
Debugging has finished
Commonly, the Error is generated Either while pressing pushButton_continue from MainWindow.c or While pressing pushButton_Save from CamCapture.c
Unable to find any solution on google.
Need some suggestions/help/link to solve this issue.
Thanks in advance.