How to use QAbstractVideoFilter to process frames from camera

[theshadowx]

@medyakovvit

Yes that's right, there is one porblem in the code is that with you code I get a greenscale. So to convert to grayscale the solution is that instead of 0 for chroma, it should be 127 (http://stackoverflow.com/a/20609599/2775917) :

void YUVFilterRunnable::deleteColorComponentFromYUV(QVideoFrame *input)
{
    // Assign 0 to Us and Vs
    int firstU = input->width()*input->height(); // if i correctly understand YUV420
    int lastV = input->width()*input->height() + input->width()*input->height()/4*2;
    uchar* inputBits = input->bits();

    for (int i=firstU; i<lastV; i++)
        inputBits[i] = 127;
}

Thanks a lot for your help

[medyakovvit]

@theshadowx I'm glad to help

[cs_a994]

Hello!

Is it possible to use the QVideoFilterRunnuble without QML?

As an example I would like to embed it into Camera example ( http://doc.qt.io/qt-5/qtmultimediawidgets-camera-example.html ) to be able to change data format.

Thank you.

[medyakovvit]

@cs_a994 Don't think so. But you can try to subclass QAbstractVideoSurface.

[cs_a994]

@medyakovvit

Thank you. I know about this way. But use of filters seams to me more neat.

I tryed to use filters with QML ( in the Camera example ) and did not yet get a result.

[medyakovvit]

@cs_a994
OK. I f you have a questions about qml camera and filters, I will try to help you.

[theshadowx]

@cs_a994

I have put a QtQuick app in github using QAbstractVideoFilter with OpenCV.

I hope it helps you.

Cheers

[cs_a994]

@theshadowx

Thank you very much. I'll study it soon. I hope it will help.

[mikeitexpert]

@theshadowx

I get the below error if I try the canny code from git hub. (https://github.com/theshadowx/Qt_OpenCV)

I don't know much about mql but I know QT intermediately.

Thank you

01:45:55: Starting /home/mike/Downloads/Qt_OpenCV-master/QtQuick/build-CannyQml-Desktop_Qt_5_12_0_GCC_64bit-Debug/CannyQml...
QML debugging is enabled. Only use this in a safe environment.

(CannyQml:24471): GStreamer-CRITICAL **: 01:45:57.866: write map requested on non-writable buffer
01:45:57: The program has unexpectedly finished.
01:45:57: The process was ended forcefully.
01:45:58: /home/mike/Downloads/Qt_OpenCV-master/QtQuick/build-CannyQml-Desktop_Qt_5_12_0_GCC_64bit-Debug/CannyQml crashed.

[theshadowx]

@mikeitexpert
Could you add this issue in https://github.com/theshadowx/Qt_OpenCV/issues

Thanks

[mikeitexpert]

here: https://github.com/theshadowx/Qt_OpenCV/issues/5

Is there any way I can convert qml to c++ code just to get an idea how your methods works in pure C++?

Thank you

[mikeitexpert]

Please let me know if there is any update on this.

Mike