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• Link to ffmpeg libraries using mingw c++ -> undefined reference [duplicate]

  16 juillet 2016, par Gerhard

  This question already has an answer here :

  • Libav linking error : undefined references
    
    3 answers
    

  I read about a lot of very similar problems here, but none of them seems
  to solve my problem. I feel that I need only a very small step to succeed...

  I have an existing c++ project and try to include some FFmpeg functions.
  When linking with MinGW on Windows OS against the FFmpeg libraries, I get always
  the error message "undefined reference to...".

  I reduced my code totally to the following sample :

  // START of file simple.cpp
  
  #ifndef INT64_C
  
  #define INT64_C(c) (c ## LL)
  
  #define UINT64_C(c) (c ## ULL)
  
  #endif
  
  
  
  #include 
  
  
  
  #include <libavutil></libavutil>opt.h>
  
  #include <libavcodec></libavcodec>avcodec.h>
  
  #include <libavutil></libavutil>channel_layout.h>
  
  #include <libavutil></libavutil>common.h>
  
  #include <libavutil></libavutil>imgutils.h>
  
  #include <libavutil></libavutil>mathematics.h>
  
  #include <libavutil></libavutil>samplefmt.h>
  
  
  
  int main(int argc, char **argv){
  
      avcodec_register_all();
  
      return 0;
  
  }
  
  // END of file simple.cpp

  I compile with :

  g++ -o simple.o -c simple.cpp -std=gnu++11

  which worked well.
  My link command is :

  g++ -o simple.exe simple.o -lavcodec -std=gnu++11

  and I get the error message :

  simple.o:simple.cpp:(.text+0xc): undefined reference to avcodec_register_all()

  So, at least the libraries are found ;-)
  I used the libraries directly from Zeranoe and I also managed to compile
  new ones from source. The error message is the same in both cases.

  A step to find the solution might be the following test (compile with gcc instead of g++) :

  1. I rename simple.cpp to simple.c

  2. I compile with :

     gcc -o simple.o -c simple.c

  3. I link with :

     g++ -o simple.o -c simple.c -lavcodec

  And that will work !!!

  But, unfortunately, that is no solution for me, because my main program
  is definitely c++ und must be compiled using g++.

  So, what the hell is wrong here ?
  Is that a FFmpeg topic or is that a gcc/g++ topic ?
  Please, all hints are welcome.

  I already tried out all possible ’extern’ and extern "C"- statements, no success.

• Revision 16248 : les boutons action doivent toujours rester inline, meme sans la class link

  23 septembre 2010, par cedric@… — Log

  les boutons action doivent toujours rester inline, meme sans la class link

• lavfi : add helpers to consume frames from link FIFOs.

  20 décembre 2016, par Nicolas George

  lavfi : add helpers to consume frames from link FIFOs.
  

  • [DH] libavfilter/avfilter.c
  • [DH] libavfilter/filters.h