Thread Implimentation:Spiking the CPU usage and hang the app and system.
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I have to show 30 FPS(Frames per second on the QT window), the frames i am receiving is YUV format( Only Y plane has been sent).
- I have implemented a thread which receives the frames and enqueque in a queque.
- Another thread which do following things
a) dequeue the frame extract the Y plane
b)used opencv to convert it to mat (cv::Mat m = cv::cvarrToMat(img11);
c)used opencv to convert the format cv::cvtColor(m,m,CV_YUV2RGB);
c)Crated QIMAGE
QImage qimg = QImage((const unsigned char*) m.data,
// m.cols, m.rows,
// QImage::Format_RGB888); // convert to QImage
d)passed it to label to show the image.
The issue i am facing is it is taking 200percent CPU isage and hangs the computer after running for a minute. Since the frames are coming at the rate of 30 fps it keeps bot the thread busy and also we need to achieve this in order to not loose a single frame, i tried usleep and yeild to make the threads free the resources however its not helping me out, it is having same behavior of hanging the system after a minute.
Kindly provide your inputs for best possible solution to achieve this.
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Perhaps SIMD operations can also speed things up for your case, as it looks that for each pixel, exactly the same operation is necessary.
Additional hint - measure how long it takes for you to process single frame. If it takes longer than the time you've got, you need to optimize the algorithm. Perhaps less conversions/ copying would help. Less info sharing between threads could improve things, too. As well as adding a buffer on UI thread, so that synchronization of painting on QLabel does not jam your other threads.
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I have to show 30 FPS(Frames per second on the QT window), the frames i am receiving is YUV format( Only Y plane has been sent).
- I have implemented a thread which receives the frames and enqueque in a queque.
- Another thread which do following things
a) dequeue the frame extract the Y plane
b)used opencv to convert it to mat (cv::Mat m = cv::cvarrToMat(img11);
c)used opencv to convert the format cv::cvtColor(m,m,CV_YUV2RGB);
c)Crated QIMAGE
QImage qimg = QImage((const unsigned char*) m.data,
// m.cols, m.rows,
// QImage::Format_RGB888); // convert to QImage
d)passed it to label to show the image.
The issue i am facing is it is taking 200percent CPU isage and hangs the computer after running for a minute. Since the frames are coming at the rate of 30 fps it keeps bot the thread busy and also we need to achieve this in order to not loose a single frame, i tried usleep and yeild to make the threads free the resources however its not helping me out, it is having same behavior of hanging the system after a minute.
Kindly provide your inputs for best possible solution to achieve this.
@Monalisa also, additionally to what the others said,
how to you pass data between threads?
Signal/Slot is, generally speaking, thread safe but it comes with a non neglectable overhang, and using a low lvl api like QMutext could/should be faster
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I think you are taking too many steps. If I understand the use case correctly, you are only getting the Y data. Therefore the color components are gone and you are really looking at a gray scale image. A faster implementation would be:
- Dequeue and extract the Y data into an array of 8 bit values
- Create a QImage with a format of QImage::Format_Indexed8 and a pre-defined gray scale color table using the 8 bit data.
That's it. There is no need to involve openCv to convert the image to YUV2 and then create an RGB image that's essentially shades of gray.
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Hi and welcome to devnet,
To add to my fellows good suggestions:
- Where are you getting the images from ?
- What size are they ?
