Recherche avancée

Sur d’autres sites (9827)

• 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.

  


• Keep getting WIN32Exception when running FFMPEG in ASP.NET project

  23 octobre 2014, par Lance Bloom

  I have an ASP.NET project and I want to use FFMPEG to help create thumbails for my videos. I’ve loaded FFMPEG into the project, and whenever I run my code I get the same error :

  ’ffmpeg.MainModule’ threw an exception of type ’System.ComponentModel.Win32Exception’
  "A 32 bit processes cannot access modules of a 64 bit process."

  I’m using VS 2013, and I’ve set my target platform to x86, and made 100% sure I am using the 32bit version of ffmpeg. I’m using the static libraries from this site (http://ffmpeg.zeranoe.com/builds/) I also tried to change the target platform to All CPUs or x64, and tried with both 32 and 64 bit versions of FFMPEG. Always the same error. I am running IIS Express when I test in my local environment.

  Here is my code. Would appreciate any help !

  String vSource = "http://example.com/myvideo.mp4";
  
  String path1 = HttpContext.Current.Request.PhysicalApplicationPath;
  
  
  
  Process ffmpeg = new Process();
  
  ProcessStartInfo startinfo = new ProcessStartInfo(HostingEnvironment.MapPath("~/App_Data/exe/ffmpeg.exe"), "-i " + vSource + "-ss 00:00:05.000 -f image2 -vframes 1 " + path1 +"thumbnail1.jpg");
  
  
  
  startinfo.RedirectStandardError = true;
  
  startinfo.RedirectStandardOutput = true;
  
  startinfo.RedirectStandardInput = true;
  
  startinfo.UseShellExecute = false;
  
  startinfo.CreateNoWindow = true;
  
  ffmpeg.StartInfo = startinfo;
  
  
  
  ffmpeg.Start();

• doc/general : fix project name after 2b1a6b1ae

  5 avril 2017, par Clément Bœsch

  doc/general : fix project name after 2b1a6b1ae
  

  • [DH] doc/general.texi