Recherche avancée

Sur d’autres sites (9126)

• Undefined reference to avcodec_alloc_context but ffmpeg linker order correct ?

  24 juillet 2014, par user2212461

  I want to build a statically linked executable statically linked to libavcodec and libavformat.
  The static ffmpeg library was build with :

  ./configure --enable-static --enable-gpl --enable-nonfree --disable-vaapi 
  
       --disable-libopus --prefix=myBuild --disable-swresample

  The linkers are set as follows :

  g++ -O2 -static -o myBin myBin-myBin.o someotherlibraries.a 
  
       -L/ffmpeg/myBuild/lib -lavformat -lavcodec -lavutil  -lrt -lm -lpthread -lz

  When compiling, I get ONLY ONE error message > :-/

  src/ffmpeg/myProgram.cpp:115: error: undefined reference to 'avcodec_alloc_context'

  Output of nm /ffmpeg/myBuild/lib/libavcodec.a | grep avcodec_alloc_context :

           U avcodec_alloc_context3
  
           U avcodec_alloc_context3
  
  000003c0 T avcodec_alloc_context3
  
           U avcodec_alloc_context3

  I include libavcodec.h with extern "C" {} and I believe my static linker order is correct. Why do I get this error ? Is it because this method has been deprecated ? How can I solve this ?

  SOLUTION :

  Dont use

  avCtx = avcodec_alloc_context()

  from maybe older code snippets, but use

  codec = avcodec_find_decoder(CODEC_ID_XYZ);//for completeness but should be the same as before
  
  avCtx = avcodec_alloc_context3(codec)

• How to load correct libavcodec.so shared library version ? (53)

  17 juillet 2014, par user2212461

  I am using libavcodec and libavformat in my project but when I execute a binary which was built on another machine, I get the following error :

  error while loading shared libraries: libavcodec.so.53: cannot open shared object file: No such file or directory

  I installed ffmpeg with libav and trying the following commands :

  sudo apt-get install ffmpeg libavcodec-dev libavformat-dev
  
  sudo apt-get install ffmpeg libavcodec-extra-53
  
  sudo apt-get install libav-tools

  The error doesnt show up when I build the binary on the same machine, but it would be much faster to compile on a second machine.

  UDPATE : I also ran sudp apt-get install update and sudo apt-get install pkg-config without any change in the output. (OS = 12.04)

• ffmpeg - which video rate is correct ?

  7 mai 2014, par mast kalandar

  I am using ubuntu 13.04

  Version of ffmpeg is ffmpeg version N-61041-g52a2138

  Through php, I am calling ffmpeg commands to extract images and do some modification in those images and again merge those images back to video.

  While merging all images through ffmpeg command, I need to pass video bit rates.

  Command is as below

  public function mergeImagesToVideo($frame_no,$user_directory_name,$video_bit_rates,&$output,&$status){
  
          /* merge all of frames to create one second video */
  
  
  
          $user_frames_path=$GLOBALS["all_user_dir_path"].$user_directory_name."/";
  
  
  
          $command= $GLOBALS['ffmpeg'].' -f image2 -r 30 -i '.
  
                    $user_frames_path.'f'.$frame_no.'_%d.png -r 30 -b:v '
  
                    .$video_bit_rates.'k '.$user_frames_path.'f'.$frame_no.'.mp4';
  
  
  
          //echo $command;
  
          exec($command,$output,$status);
  
          return;
  
      }

  The call is made as below

  $this->mergeImagesToVideo($start_second,$user_directory,$video_bit_rates,$output,$status);
  
  
  
                if($status!=0){
  
                  echo "some thing went wrong in merging all images to create a video <br />";
  
                }

  Now When check bit rates through ffmpeg command output is like as below

  ffmpeg -i f1.mp4

  This command shows 7303 kb/s

  

  While I right click the image and show properties, it shows 7295 kbps

  

  Which is the correct one ?? Not getting correct line..

  Thanks in advance.