Repository: opencv
Issue: videoio: MSMF: Doesn't save convertFormat property, no way to read raw video
Labels: priority: low,category: videoio(camera),platform: win32

##### System information (version)
- OpenCV => 4.2, 4.3-pre (master)
- Operating System / Platform => Windows 10 64 Bit
- Compiler => Visual Studio 2019

##### Detailed description

I am trying to read a video from an uncompressed grayscale 8-bit AVI file without changing the color format. In OpenCV 3.4 this was easily possible. In OpenCV 4.0 this was possible but I had to set CAP_PROP_CONVERT_RGB to false and reshape the frames because they would be read as 1 x size instead of width x height. In OpenCV 4.2, it looks like CAP_PROP_CONVERT_RGB isn't stored at all.

I think this was broken in 6c8f50d1f3f99

##### Steps to reproduce

    ```.cpp
    cv::VideoCapture cap("testfile.avi", cv::CAP_MSMF);
    std::cout << cap.get(cv::CAP_PROP_CONVERT_RGB) << std::endl; // Prints 1
    cap.set(cv::CAP_PROP_CONVERT_RGB, false);
    std::cout << cap.get(cv::CAP_PROP_CONVERT_RGB) << std::endl; // Prints 1
    cv::Mat frame;
    cap >> frame;
    // prints 760x760 ch: 3   for a 760x760 grayscale image
    std::cout << "raw: " << frame.cols << "x" << frame.rows << " ch: " << frame.channels();
    ```

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