i think i find answer, i must use this code :
processFramesThread.pause();
videoCapture.release();
videoCapture.open(0);
videoCapture.set(cv::CAP_PROP_FRAME_WIDTH, width);
videoCapture.set(cv::CAP_PROP_FRAME_HEIGHT, height);
processFramesThread.resume();
But this takes about 10 seconds, in other apps it takes about 1 second, and it shows these 2 warnings, what’s wrong with me?
[ WARN:0] global F:.…\OpenCV\4.5.4\opencv\modules\videoio\src\cap_msmf.cpp (438) `anonymous-namespace’::SourceReaderCB::~SourceReaderCB terminating async callback
[ WARN:1] global F:.…\4.5.4\opencv\modules\videoio\src\cap_msmf.cpp (1022) CvCapture_MSMF::grabFrame videoio(MSMF): can’t grab frame. Error: -2147483638
My function to check frames :
void file_webcam::ProcessWebcamFrames(QString name)
{
cv::Mat frame;
QString fileName;
QString currentTime;
QLocale testLocale = QLocale(QLocale::English, QLocale::UnitedStates);
//---
double contrast;
int brightness;
//---
// list of resolution standards in computer monitors
// https://en.wikipedia.org/wiki/List_of_common_resolutions
// https://en.wikipedia.org/wiki/Graphics_display_resolution
QVector<QVector<int>> standardResolutions =
{
{160, 120},
{192, 144},
{256, 144},
{240, 160},
{320, 240},
{360, 240},
{384, 240},
{400, 240},
{432, 240},
{480, 320},
{480, 360},
{640, 360},
{600, 480},
{640, 480},
{720, 480},
{768, 480},
{800, 480},
{854, 480},
{960, 480},
{675, 540},
{960, 540},
{720, 576},
{768, 576},
{1024, 576},
{750, 600},
{800, 600},
{1024, 600},
{960, 640},
{1024, 640},
{1136, 640},
{960, 720},
{1152, 720},
{1280, 720},
{1440, 720},
{960, 768},
{1024, 768},
{1152, 768},
{1280, 768},
{1366, 768},
{1280, 800},
{1152, 864},
{1280, 864},
{1536, 864},
{1200, 900},
{1440, 900},
{1600, 900},
{1280, 960},
{1440, 960},
{1536, 960},
{1280, 1024},
{1600, 1024},
{1400, 1050},
{1680, 1050},
{1440, 1080},
{1920, 1080},
{2160, 1080},
{2280, 1080},
{2560, 1080},
{2048, 1152},
{1500, 1200},
{1600, 1200},
{1920, 1200},
{1920, 1280},
{2048, 1280},
{1920, 1440},
{2160, 1440},
{2304, 1440},
{2560, 1440},
{2880, 1440},
{2960, 1440},
{3040, 1440},
{3120, 1440},
{3200, 1440},
{3440, 1440},
{5120, 1440},
{2048, 1536},
{2400, 1600},
{2560, 1600},
{3840, 1600},
{2880, 1620},
{2880, 1800},
{3200, 1800},
{2560, 1920},
{2880, 1920},
{3072, 1920},
{2560, 2048},
{2732, 2048},
{3200, 2048},
{2880, 2160},
{3240, 2160},
{3840, 2160},
{4320, 2160},
{5120, 2160},
{3200, 2400},
{3840, 2400},
{3840, 2560},
{4096, 2560},
{5120, 2880},
{5760, 2880},
{4096, 3072},
{7680, 4320},
{10240, 4320},
};
//QVector<QVector<int>> possibleResolutions(1000, QVector< int >(2));
while(true)
{
ShowMessageOnStatusBar();
if(videoCapture.isOpened())
{
// Find All Possible Webcam Resolutions [ only 1 time ]
if(allPossibleResolutionsFinded == false)
{
for(int i = 0; i < standardResolutions.count(); i++)
{
int w = standardResolutions[i][0];
int h = standardResolutions[i][1];
videoCapture.set(cv::CAP_PROP_FRAME_WIDTH, w);
videoCapture.set(cv::CAP_PROP_FRAME_HEIGHT, h);
int _w = videoCapture.get(cv::CAP_PROP_FRAME_WIDTH);
int _h = videoCapture.get(cv::CAP_PROP_FRAME_HEIGHT);
if(w == _w && h == _h)
{
QString item = QString("%1x%2").arg(w).arg(h);
ui->comboBox_PossibleResolutions->addItem(item);
}
}
qDebug() << "END!";
allPossibleResolutionsFinded = true;
}
// read next frame
videoCapture >> frame;
if(frame.empty() == false)
{
// increase frame counter
numberFramesAfterConnect++;
// apply effects on frame
contrast = (double)ui->horizontalSlider_Contrast->value() / 100.0; // 1 to 5
brightness = ui->horizontalSlider_Brightness->value(); // -255 to 255
frame.convertTo(frame, -1, contrast, brightness);
// show frame
cv::cvtColor(frame, frame, cv::COLOR_BGR2RGB); // Qt reads in RGB whereas CV in BGR
QImage image((uchar*)frame.data, frame.cols, frame.rows, frame.step, QImage::Format_RGB888); // Converts the CV image into Qt standard format
ui->label_Image->setPixmap(QPixmap::fromImage(image)); // display the image in label that is created earlier
// if start button pressed
if(isStarted)
{
// save frame as image
if(canSaveImageNow)
{
currentTime = testLocale.toString(QDateTime::currentDateTime(), "hh-mm-ss.zzz");
fileName = LastDirectoryPath_SaveImageVideo + "/" + QString::number(numberFramesAfterConnect) + ") " + currentTime + ".jpg";
image.save(fileName);
canSaveImageNow = false;
}
// save frame as video
}
}
}
}
}
