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• AccessViolationException occurred in AForge.Video.FFMPEG.dll

  4 août 2018, par Prakash M

  I have a camera class, in this class I used a timer and in its tick event I am saving video using AForge.Net’s VideoFileWriter in C++/Cli (x86, .net framework : v4.6).
  This is not supposed to happen, as this is managed code. But even if I wrap in try catch block, program crashes because of AccessViolationException. I have verified that Image is not null. Something to do with VideoFileWriter. This happens anytime between app start to 30 minutes of running.

  An unhandled exception of type ’System.AccessViolationException’
  occurred in AForge.Video.FFMPEG.dll
  Additional information : Attempted to read or write protected memory.
  This is often an indication that other memory is corrupt.

  In Visual Studio’s output I see

  Exception thrown at 0x0C4D689F (swscale-2.dll) in test.exe : 0xC0000005 : Access violation writing location 0x09F83D80.
  Exception thrown : ’System.AccessViolationException’ in
  AForge.Video.FFMPEG.dll

  code :

   private: System::Void Video_Recorder_Tick(System::Object^  sender, System::Timers::ElapsedEventArgs^  e)
  
    {
  
        Bitmap^ save = ConvertMatToBitmap(image); //function to convert opencv's Mat to .net's Bitmap        
  
        if(writer!= nullptr)
  
         writer->WriteVideoFrame(save);
  
         delete save;
  
     }
  
  
  
    VideoFileWriter ^writer = gcnew VideoFileWriter();
  
  
  
    private: Void load_VideoWriter()
  
    {
  
      writer->Open("C:/video.avi", 640, 480, 10, VideoCodec::Default);        
  
    }

  Visual Studio showed few values for writer

  BitRate 400000
  Codec Default
  FrameRate 10
  Height 480
  IsOpen true
  Width 640
  

  Let me know if anybody needs more info.
  call stack didn’t help much

  

  To my surprise no one on internet is having this issue !
  Code seems straight forward, what could possibly be the issue ?

• How to configure FFmpeg library with ndk r12 using windows 7 64 bit operating system for android

  13 juillet 2016, par jack

  I want to merge mp3 audio file with surfaceview recorded video in background. So after lots of research i get FFmpeg concept for achieving this kind of functionality. But i am not know how to configure Ffmpeg library with ndk in android studio using windows 7 64 bit os. So if any one can have knowledge about it so please share with me. Thank you in advance.

  

• Emscripten : Linking library to project

  13 avril 2021, par locust

  I'm trying to build a small project that uses ffmpeg library to WebAssembly, with use of Emscripten. Before that, I tried it out by transpiling some simple program from C into Wasm and it worked fine, but that time I was not using any additional libraries.

  


  For C++ I'm working with Visual Studio and FFmpeg I linked in project's "Properties" as follows :

  


  


  1. all .h header files I placed in "include" catalog and I added it as "Additional Include Directories" in "C/C++" section

     


  


  2. all .lib and .dll.a (for example avcodec.lib or libavcodec.dll.a) files I placed in "lib" and added as "Additional Library Directories" in "Linker" section

     


  


  


  All includes and the program itself works fine, so now I was trying to prepare a Wasm module with Emscripten with the same same command that I used earlier, but already knowing that is not going to work :

  


  em++ cut_video.cpp -Os -g1 -L lib -I include -s WASM=1 -s FORCE_FILESYSTEM=1 -s ALLOW_MEMORY_GROWTH=1 -s EXPORT_ES6=1 -s MODULARIZE=1 -s "EXPORT_NAME='Editor'" -s "ENVIRONMENT='web'" -s EXPORTED_FUNCTIONS="['_doubler', '_cut_video', '_cut_video1']" -s ERROR_ON_UNDEFINED_SYMBOLS=0  -s ASSERTIONS=1 --bind -o cutter.js


  


  I added the "-I include" parameter which is suppose to be pointing to the same header files, that I mentioned above, and it seems to be fine for Emscripten, because the initial error was solved by it.
Emscripten already found out the problem with functions from ffmpeg library, so I added "ERROR_ON_UNDEFINED_SYMBOLS=0" just to see what will happen when I will add this module to front-end app. Obviously it end up with error "missing function : av_register_all", which is first ffmpeg function within my code.

  


  All explanations that can be helpful I found really unclear for me, because generally I'm not working with C++ or Linux environment, so I'm not fimilliar with Makefile or so.

  


  Is there a way, basing on what I described and how my project was prepared with Visual Studio, to tell the Emscripten to use those pre-build .dll.a or .lib files of FFmpeg for my app ? Or how should I modify my project to make it acceptable for Emscripten ?

  


  Edit : Since cut_video.cpp file is quite big, maybe it's a better idea to just paste here a link to this file on github instead of the big block of code.