How to use QAbstractVideoFilter to process frames from camera
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@medyakovvit Hi, thanks for responding, I hope everything is fine for you.
if my camera takes video in RGB32 it would be easier as I can create QImage from the edge matrix and then create a QVideoFrame from QImage.:
///cv::Mat to QImage QImage ImgDest(edges.data, edges.cols, edges.rows, edges.step, QImage::Format_RGB888); QVideoFrame *output = new QVideoFrame(ImgDest);And then I would return the output.
The problem (From what I understood) is that my camera generates images with YUV color scheme. which means that QVideoSurfaceFormat is in YUV, so if I use RGB32 format it won't work.
Unfortunately QImage doesn't support YUV format. :(
wrote on 18 Sept 2015, 08:17 last edited by@theshadowx So, if correctly understood this YUV420 and YUV format, Y - luma component, U and V - color component. And in single frame Ys go first, then Us and Vs. So if you need grayscale image, you can work with Ys and ignore Us and Vs. Maybe you can try:
QVideoFrame YUVFilterRunnable::run(QVideoFrame *input, const QVideoSurfaceFormat &surfaceFormat, QVideoFilterRunnable::RunFlags flags) { if (!input->isValid()) return *input; input->map(QAbstractVideoBuffer::ReadWrite); this->deleteColorComponentFromYUV(input); cv::Mat mat(input->height(),input->width(), CV_8UC1, input->bits()); // create grayscale mat with input's Ys only and avoid additional color conversion and copying cv::GaussianBlur(mat, mat, Size(7,7), 1.5, 1.5); cv::Canny(mat, mat, 0, 30, 3); input->unmap(); return *input; } 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] = 0; } -
@theshadowx So, if correctly understood this YUV420 and YUV format, Y - luma component, U and V - color component. And in single frame Ys go first, then Us and Vs. So if you need grayscale image, you can work with Ys and ignore Us and Vs. Maybe you can try:
QVideoFrame YUVFilterRunnable::run(QVideoFrame *input, const QVideoSurfaceFormat &surfaceFormat, QVideoFilterRunnable::RunFlags flags) { if (!input->isValid()) return *input; input->map(QAbstractVideoBuffer::ReadWrite); this->deleteColorComponentFromYUV(input); cv::Mat mat(input->height(),input->width(), CV_8UC1, input->bits()); // create grayscale mat with input's Ys only and avoid additional color conversion and copying cv::GaussianBlur(mat, mat, Size(7,7), 1.5, 1.5); cv::Canny(mat, mat, 0, 30, 3); input->unmap(); return *input; } 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] = 0; }wrote on 18 Sept 2015, 13:27 last edited by theshadowxYes 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
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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
wrote on 18 Sept 2015, 15:55 last edited by@theshadowx I'm glad to help
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wrote on 22 Sept 2015, 13:46 last edited by
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.
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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.
wrote on 25 Sept 2015, 05:30 last edited by@cs_a994 Don't think so. But you can try to subclass QAbstractVideoSurface.
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@cs_a994 Don't think so. But you can try to subclass QAbstractVideoSurface.
wrote on 25 Sept 2015, 13:14 last edited byThank 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.
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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.
wrote on 25 Sept 2015, 16:35 last edited by@cs_a994
OK. I f you have a questions about qml camera and filters, I will try to help you. -
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.
wrote on 25 Sept 2015, 22:00 last edited by -
wrote on 28 Sept 2015, 12:33 last edited by
Thank you very much. I'll study it soon. I hope it will help.
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wrote on 4 Jan 2019, 21:28 last edited by mikeitexpert 1 Apr 2019, 23:21
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. -
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.wrote on 5 Jan 2019, 08:15 last edited by@mikeitexpert
Could you add this issue in https://github.com/theshadowx/Qt_OpenCV/issuesThanks
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wrote on 5 Jan 2019, 08:32 last edited by
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
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wrote on 7 Jan 2019, 08:34 last edited by
Please let me know if there is any update on this.
Mike