Regarding the saving the image in Android using QVideoProbe

Pradeep Kumar

Hi,

I want to get the frames in video mode, i have used QML Camera, and QVideoProbe Class to get the frames. I am getting the frames but all the images are blank, i saw the size it is not 0 kb size, it was of 51.14 kb.

And retreived the image and displayed in QLabel.
It is blank.

Here is the image

https://postimg.org/image/ircprtnd7/

Guidance is required.

Thanks,

raven-worx

@Pradeep-Kumar said in Regarding the saving the image in Android using QVideoProbe:

Guidance is required.

code is required ;)

Pradeep Kumar

Hi the code snippet

void className::funcName(){ 
        cam_ = new QQuickWidget();
        context_ = cam_->engine()->rootContext();
        context_->setContextProperty("MyWidget", this);
        cam_->setSource(QUrl("qrc:///declarative-camera.qml"));
        m_qmlCameraQObject = cam_->rootObject()->children().at(0)->findChild<QObject*>("CameraObject");
        QVariant mediaObject = m_qmlCameraQObject->property("mediaObject");

        if(mediaObject.isValid()){

            qDebug()<<"----Variant object is valid----- \n";

            m_QCameraObj = mediaObject.value<QCamera*>();
        
       if(m_QCameraObj && m_QCameraObj->availability() == QMultimedia::Available){

                m_videoProbe = new QVideoProbe(this);
                if(m_videoProbe->setSource(m_QCameraObj)){

 connect(m_videoProbe, SIGNAL(videoFrameProbed(QVideoFrame)), this, SLOT(manageVideoFrame(QVideoFrame)));

                  }
           }
      }
}

And in the slot:

void ClassName::manageVideoFrame(QVideoFrame frame)
{
        QVideoFrame cloneFrame(frame);
        cloneFrame.map(QAbstractVideoBuffer::ReadOnly);

        QImage::Format imageFormat;
        if((imageFormat = QVideoFrame::imageFormatFromPixelFormat(cloneFrame.pixelFormat())) == QImage::Format_Invalid)
        {

            QImage image(cloneFrame.size(), QImage::Format_ARGB32);

            if (!image.isNull())
            {

                QDateTime dateTime = dateTime.currentDateTime();
                QString dateTimeString = dateTime.toString("yyyyMMddhhmmss");

                QString appendString = "image_";
                appendString.append(dateTimeString);

                QString str = "/storage/sdcard1/DCIM/";
                str.append(appendString+".jpg");
        }
   }
}

jsulm

@Pradeep-Kumar said in Regarding the saving the image in Android using QVideoProbe:

if((imageFormat = QVideoFrame::imageFormatFromPixelFormat(cloneFrame.pixelFormat())) == QImage::Format_Invalid)

Shouldn't it be != instead of == here:

if((imageFormat = QVideoFrame::imageFormatFromPixelFormat(cloneFrame.pixelFormat())) == QImage::Format_Invalid)

You create a image:

QImage image(cloneFrame.size(), QImage::Format_ARGB32);

but you do not write any data into that image and I cannot see where you actualy save the image.

Pradeep Kumar

Hi,

Sorry about that , i have used save method.

       if (!image.isNull())
        {

            QDateTime dateTime = dateTime.currentDateTime();
            QString dateTimeString = dateTime.toString("yyyyMMddhhmmss");

            QString appendString = "image_";
            appendString.append(dateTimeString);

            QString str = "/storage/sdcard1/DCIM/";
            str.append(appendString+".jpg");

            if (image.save(str, "JPG"))
            {
                qDebug()<<"Image saved successfully \n";
            }
            else
            {
                qDebug()<<"There is problem in image saving \n";
            }
    }

Image is inserted successfully.

Thanks,

Pradeep Kumar

Hi,

Is the code not valid or am i missing something?.

Thanks,

jsulm

@Pradeep-Kumar As I said before I cannot see where you're writing anything into image.
You only create one:

QImage image(cloneFrame.size(), QImage::Format_ARGB32);

but never write any pixel data into it.

Pradeep Kumar

Can u clarify and correct the previous code snippet .
Correct me if i am wrong , i didnt assign the frames captured to QImage, is that the point?.

Thanks,

jsulm

@Pradeep-Kumar Yes, you do not write anything into the image.
QVideoFrame documentation says:
"The pixel contents of a video frame can be mapped to memory using the map() function. While mapped, the video data can accessed using the bits() function, which returns a pointer to a buffer."
So, first you need to map the frame data into memory calling http://doc.qt.io/qt-5/qvideoframe.html#map, then you can access the frame data using http://doc.qt.io/qt-5/qvideoframe.html#bits and write the data into the image via http://doc.qt.io/qt-5/qimage.html#loadFromData.