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• ffmpeg/libav with Qt Creator - unresolved external symbol

  12 septembre 2015, par Alexandre

  I am attempting to integrate ffmpeg into my C++/Qt application in Qt Creator. I have tried to make it as barebones as possible to isolate the problem.
  I am using Zeranoe’s 32-bit ffmpeg dev build.

  Here is the error returned :

  main.obj :-1 : error : LNK2019 : unresolved external symbol av_register_all referenced in function main

  Here is ffmpegTest.pro :

  INCLUDEPATH += $$PWD/ffmpeg/include
  
  
  
  TARGET = ffmpegTest
  
  
  
  SOURCES += main.cpp
  
  
  
  LIBS += -L$$PWD/ffmpeg/lib\
  
          -lavcodec\
  
          -lavformat\
  
          -lavdevice\
  
          -lswscale\
  
          -lavutil\
  
          -ldsound\

  And here is main.cpp :

  extern "C"{
  
      #include <libavcodec></libavcodec>avcodec.h>
  
      #include <libavformat></libavformat>avformat.h>
  
  }
  
  
  
  int main(int argc, char *argv[])
  
  {
  
      av_register_all();
  
  }

  And here is a screenshot of the project directory :

  http://i.stack.imgur.com/enqmg.png (I do not have enough reputation to embed an image)

  Inside the ffmpeg directory is Zeranoe’s build.

• symbol lookup error with FFmpeg

  8 mars 2017, par Tobias Geiselmann

  I am writing a Java application which uses FFmpeg. Therefore I use JNI to execute some native code. Compiling my shared object works without problems, but when I execute my code I get the following error :

  /usr/local/jamaica-6.3-1/target/linux-x86_64/bin/jamaicavm_bin: symbol lookup error: /home/tobi/workspace/sender/lib/libsender.so: undefined symbol: av_frame_alloc

  av_frame_alloc is a method of FFmpeg’s libavutil library. I linked my shared object against a few FFmpeg libraries (such as libavcodec, libavutil, etc.), but I’m not able to execute methods from libavutil.
  When I run the nm command to list all the symbols from the object file, I get the following result :

  tobi@tobi:~/workspace/sender/lib$ nm libsender.so 
  
               U avcodec_alloc_context3@@LIBAVCODEC_54
  
               U avcodec_copy_context@@LIBAVCODEC_54
  
               U avcodec_find_decoder@@LIBAVCODEC_54
  
               U avcodec_find_encoder@@LIBAVCODEC_54
  
               U avcodec_open2@@LIBAVCODEC_54
  
               U av_dump_format@@LIBAVFORMAT_54
  
               U avformat_find_stream_info@@LIBAVFORMAT_54
  
               U avformat_open_input@@LIBAVFORMAT_54
  
               U av_frame_alloc
  
               U av_image_alloc@@LIBAVUTIL_52
  
               U av_log@@LIBAVUTIL_52
  
               U av_register_all@@LIBAVFORMAT_54

  So, obviously, there is something wrong with av_frame_alloc. Why do I get a symbol lookup error every time I want to call av_frame_alloc ?

  Thanks !

• build : add Solaris symbol versioning

  7 octobre 2015, par Sean McGovern

  build : add Solaris symbol versioning
  The versioning facility in the Solaris linker differs from Linux in 3 ways :
  1. It does not support globs in linker scripts for
  
  symbol versioning — this is a GNU extension.
  2. The linker argument is ’-M’, instead of ’—version-script’.
  3. It is picky about line endings.
  
  Each symbol or directive must be on a line of it’s own.
  Let’s use make_sunver.pl from GCC to generate a version script that works
  
  correctly with the Solaris linker. It’s function is to correctly expand the
  
  globs in the original generated version script.
  Signed-off-by : Luca Barbato <lu_zero@gentoo.org>
  

  • [DBH] Makefile
  • [DBH] common.mak
  • [DBH] compat/solaris/make_sunver.pl
  • [DBH] configure