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• building c++ code into a shared library

  11 avril 2016, par gaurav

  I have some c++ code which i use as shared library in a java application.My c++ code uses some libraries like ffmpeg and boost. and ffmpeg libraries in turn depend on libx264. my first question is - can i build my c++ into a "fat" shared library which contains all the symbols from all libraries used so that on a new machine if i just copy the fat .so file everything works.
  If thats not possible then can you help me fix my current build process. This is what i am doing currently -

  1)on a local VM(ubuntu 64) i compile ffmpeg code using -fPIC flag and install h264 and boost using apt-get commands.
  2) on the same VM i compile my code using make file which looks like this-

  INCLUDES =   -I/opt/ffmpeg/include -I/usr/lib/jvm/java-7-openjdk-   amd64/include -I/usr/lib/jvm/java-7-openjdk-amd64/include/linux
  
  
  
  LDFLAGS =   -L/home/ubuntu/ffmpeg_shared
  
  
  
  LIBRARIES = -lavformat -lavcodec -lswscale -lavutil -lpthread  -lx264 -lboost_system -lboost_thread -lboost_chrono 
  
  
  
  CC = g++ -std=c++11 -fPIC
  
  
  
  all:clean final
  
  
  
  final:Api.o ImageSequence.o OverlayAnimation.o Utils.o ImageFrame.o 
  
  $(CC)  -o final.so Api.o ImageSequence.o OverlayAnimation.o Utils.o  ImageFrame.o $(LDFLAGS) $(LIBRARIES) -shared 

  3) on a new machine where java app will run. i install h264 and boost using apt-get commands and copy ffmpeg’s compiled library files to /usr/local/lib.

  4) copy the final.so file to this new machine. but when the java code tries to use the final.so file i see it tries to use wierdly named files. for example - it tries to find libavcodec.so.57 , libavformat.so.57 etc. to fix this i just created a copy of these files ie libavcodec.so copied to libavcodec.so.57.

  5)But these ffmpeg libraries in turn uses a differently named lib264.so file. on my new machine the apt-get command for x264 installed a file named libx264.so.148 but one of ffmpeg libraries is searching for file libx264.so.142 even if i rename this libx264.so file i get new errors where ffmpeg libraries tries to call libx264’s methods which has these numbers attached.

  6) at this time the only working option for me is to bring the c++ code on every new machine and build final.so file locally. this is something i want to avoid since i want to distribute the .so file along with jar file to my clients which they can easily use without having to build and install stuff.

• avfilter/vf_ssim : Fix x86 assembly code for SSIM calculation

  31 juillet 2023, par Evgeny Pavlov

  avfilter/vf_ssim : Fix x86 assembly code for SSIM calculation
  This commit fixes bug #10495
  The code had several bugs related to post-loop compensation code :
  
   test assembly instruction performs bitwise AND operation and
  
  generate flags used by jz branch instruction. Wrong test condition
  
  leads to incorrect branching
  
   Incorrect compensation code for some branches
  Signed-off-by : Evgeny Pavlov <lucenticus@gmail.com>
  

  • [DH] libavfilter/x86/vf_ssim.asm

• C Code Using FFmpeg libraries - Compilation Error

  17 août 2013, par Ardatr

  I've been recently trying to compile C code that uses the FFmpeg libraries ; however, the compilation fails due to a reason that I cannot determine.

  The code that I've been trying to compile is the filtering_audio.c file on the Doxygen Documentation website for FFmpeg (I'll provide the link, since the code is too long to quote here) : http://ffmpeg.org/doxygen/trunk/doc_2examples_2filtering_audio_8c-example.html

  I use gcc to compile the code :

      gcc filter.c -lavformat -lavcodec -lavfilter  -lavutil

  And I get the following undefined reference errors :

      /tmp/cc90K2S5.o: In function `init_filters':
  
      filter.c:(.text+0x3e5): undefined reference to `av_int_list_length_for_size'
  
      filter.c:(.text+0x407): undefined reference to `av_int_list_length_for_size'
  
      filter.c:(.text+0x42d): undefined reference to `av_opt_set_bin'
  
      filter.c:(.text+0x482): undefined reference to `av_int_list_length_for_size'
  
      filter.c:(.text+0x4a4): undefined reference to `av_int_list_length_for_size'
  
      filter.c:(.text+0x4ca): undefined reference to `av_opt_set_bin'
  
      filter.c:(.text+0x51f): undefined reference to `av_int_list_length_for_size'
  
      filter.c:(.text+0x541): undefined reference to `av_int_list_length_for_size'
  
      filter.c:(.text+0x567): undefined reference to `av_opt_set_bin'
  
      /tmp/cc90K2S5.o: In function `print_frame':
  
      filter.c:(.text+0x76b): undefined reference to `av_frame_get_channel_layout'
  
      /tmp/cc90K2S5.o: In function `main':
  
      filter.c:(.text+0x831): undefined reference to `av_frame_alloc'
  
      filter.c:(.text+0x83d): undefined reference to `av_frame_alloc'
  
      filter.c:(.text+0x9de): undefined reference to `av_buffersrc_add_frame_flags'
  
      filter.c:(.text+0xa16): undefined reference to `av_buffersink_get_frame'
  
      filter.c:(.text+0xa58): undefined reference to `av_frame_unref'
  
      filter.c:(.text+0xab6): undefined reference to `av_frame_free'
  
      filter.c:(.text+0xac5): undefined reference to `av_frame_free'
  
      collect2: error: ld returned 1 exit status

  I understand that the undefined reference error indicates that it wasn't able to find the functions referenced from filtering_audio.c, but this doesn't make sense, since these functions should exist in the FFmpeg libraries.

  Any help is appreciated, thank you !