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• UWP C# and Windows Runtime Component C++ Permission Denied error when opening file

  29 décembre 2020, par Surya Solanki

  I have developed a UWP app in C# which contains a Windows Runtime Component C++ project. the app allows the user to choose an mp4 file and passes this file to the c++ code, which then utilizes ffmpeg libraries to retrieve the presentation time stamps of a video file and output them to a file.

  


  the issue i'm facing is that the c++ code is not able to open the mp4 file when using the avformat_open_input function :

  


  int PTSExtraction::parse_file(Platform::String^ filename)
{
    int ret = 0;
    AVPacket pkt = { 0 };


    std::wstring fileNameW(filename->Begin());
    std::string fileNameA(fileNameW.begin(), fileNameW.end());
    const wchar_t* w_chars = fileNameW.c_str();
    src_filename = fileNameA.c_str(); 

    if (avformat_open_input(&fmt_ctx, src_filename, NULL, NULL) < 0) {
        fprintf(stderr, "Could not open source file %s\n", src_filename);
        return 1; 
    }
    // rest of code 
}


  


  the error received by avformat_open_input is Permission Denied. I cannot even open a random text file in this function by doing :

  


  ofstream output; 
output.open("output.txt");


  


  I realize there are file system permissions that are blocking the C++ component of my uwp app from opening files. here are the things i have tried so far :

  


  

  • i have enabled broadFileSystemAccess in the Package.appxmanifest (https://blogs.windows.com/windowsdeveloper/2018/05/18/console-uwp-applications-and-file-system-access/) - in the Capabilities section of the Package.appxmanifest file I've allowed access to Location, Pictures Library, and Videos Library.

  


  • I've checked the File System Privacy Settings on my computer and enabled my app to access the File System.

  


  • I've tried moving the mp4 file to various locations (Documents, Pictures Library, Videos Library) to see if the C++ component has access to these locations.

  


  • I've tried the solution from this post : Qt WinRT App cannot access file permission denied.

  


  


  None of these allow the C++ component to open any files. i would really appreciate if anyone has a solution for this problem.

  


• How to use v4l2 scrcpy virtual webcam ?

  2 mars 2024, par Emma bundy

  I created a virtual camera v4l2 /dev/video21 and linked it to my notebook's default webcam /dev/video1 and it started working so far ok, then I mirrored the webcam I created in OBS-studio.

  


  and now I want to connect in scrcpy the virtual camera that I created that is active /dev/video21, but I don't know how to do that, what commands to give to use the v4l2 /dev/video21 camera from the computer on my cell phone.

  


  which is already mirrored on the computer screen via wireless

  


  I need help, who can help me I thank you immensely ! This is for my college studies

  


  I tried to do this several times but I couldn't, I use Fedora 37 gnome, I used ffmpeg to link the webcam /dev/video1 + /dev/video21, and I mirrored it in OBS-studio, but I don't know which command to give to send the /dev/video21 video stream to my cell phone, use the virtual camera created on the cell phone.

  


• Anomalie #2056 (Fermé) : SPIP vierge et page d’accueil de l’espace privé

  10 mai 2011, par cedric -

  doublonne #2050