Convert IUncompressedVideoFrame to OpenCV Mat

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    Roman Inflianskas

    Anubhav,

    Here is how we (the Nx) do this:

    cv::Mat img(
        /*_rows*/ frame->height(),
        /*_cols*/ frame->width(),
        /*_type*/ CV_8UC3, //< BGR color space (default for OpenCV)
        /*_data*/ (void*) frame->data(0),
        /*_step*/ (size_t) frame->lineSize(0))
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    Anubhav Rohatgi

    How about if I choose to use yuv420 only. I believe my camera is not allowing bgr, or is there any alternative.

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    Evgeny Balashov

    The server will transcode video into a requested pixel format, it doesn't matter what specifically camera is streaming.

    Most likely you just need to choose the pixel format required for your neural network or video analytics algorithm.

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    Mohamed Thasin

    I am using the above code to store image from the video stream. But, it's coming as black and white image (grey scale). 



     

     

     

    Any idea how to get RGB image?

    I have raised  a new post regarding this issue. https://support.networkoptix.com/hc/en-us/community/posts/360043831873-saving-frames-is-returning-gray-scale-image
    it gives more details of my problem. 

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    Nx Support

    That other post explains, how you can choose pixel format.

    The key idea: there are different ways to represent color image: YUV, RGB, etc.

    You need to choose what format do you need specifically: maybe based on how your analytics model was trained, maybe based on other considerations. Then you can request that specific pixel format for the plugin using manifest.

     

    If in this example you are requesting YUV format, so data(0)  is the first component of this representation: Luminance (Y), so by saving this first component you get only brightness component, so you see grayscale image https://en.wikipedia.org/wiki/YUV

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