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• CMake specifies link libraries in wrong order [duplicate]

  18 janvier 2021, par Jamie Royer

  I'm following a youtube video on building a project with CMake and FFmpeg. The author is using a Mac and I'm using Ubuntu 20.04. I've been following along successfully until hitting this problem. cmake —version returns 3.16.3

  


  For some reason it is specifying the libraries too early so nothing is imported :

  


  ~/video-app/build# cmake ..
~/video-app/build# make VERBOSE=1
...
/usr/bin/c++ \
   -lavcodec -lavformat \                            # << Too early
   CMakeFiles/video-app.dir/src/main.cpp.o \
   CMakeFiles/video-app.dir/src/load_frame.cpp.o \
   -o video-app \                                    # << Should be here
   lib/glfw/src/libglfw3.a \
   -lGL -lGLU -lpthread /usr/lib/x86_64-linux-gnu/librt.so -lm -ldl


  


  If I manually run the command with the -l (dash ell) reordered, it compiles successfully.

  


  Here is the contents of the two CMakeLists.txt files.

  


  # video-app/CMakeLists.txt
cmake_minimum_required(VERSION 3.14)
project(video-app C CXX)
set(CMAKE_CXX_STANDARD 14)
add_subdirectory(lib/glfw)
add_subdirectory(lib/FFmpeg)
list(APPEND EXTRA_LIBS "-lGL -lGLU")
list(APPEND SOURCES src/main.cpp src/load_frame.cpp)
add_executable(video-app ${SOURCES})
target_link_libraries(video-app FFmpeg glfw ${EXTRA_LIBS})


  


  # video-app/lib/CMakeLists.txt
cmake_minimum_required(VERSION 3.14)
project(FFmpeg)
find_package(PkgConfig REQUIRED)
# There are seven libraries in original - only two shown here for brevity.
pkg_check_modules(AVCODEC   REQUIRED IMPORTED_TARGET libavcodec)
pkg_check_modules(AVFORMAT  REQUIRED IMPORTED_TARGET libavformat)
add_library(FFmpeg INTERFACE IMPORTED GLOBAL)
target_include_directories(FFmpeg INTERFACE
    ${AVCODEC_INCLUDE_DIRS}
    ${AVFORMAT_INCLUDE_DIRS})
target_link_options(FFmpeg INTERFACE
    ${AVCODEC_LDFLAGS}
    ${AVFORMAT_LDFLAGS})


  


  I tried :

  


  

  • Changing the order of target_link_libraries in top CMake file. Funny thing is, it worked once.

  


  • I tried adding target_link_libraries to FFmpeg CMake file.

  


  • Searching for stackover.com for answers and reading CMake documentation.

  


  


• how too download this link with ffmpeg

  27 décembre 2020, par Behrad kabiri

  i want download video with this command in ffmpeg :

  


  ffmpeg -i https://msx.namava.ir/hvod/2020/12/e9936676-eea2-44bd-b17b-dc5e58fd000d/v_854.mp4/index-v1-a1.m3u8?x=EgvsRR7zZLXNoaz49v4D05BwcjHwPaNSOtkB9y98QGOIB_EyAhV_hc44Z4McLT_FTwzBWxpaK1WlNgSBkLd415LU1jRGz0yFNhciw_SDSwgj6OlAQCARiRIb9UU8XMh_dMXKr4KncBfgwnYLMOlUn6zfSa3ltot63vKiuw0CUpU1 -vcodec copy output.mp4

  


  but recive this eror :

  


  [https @ 00000242dbcfeec0] HTTP error 420
https://msx.namava.ir/hvod/2020/12/e9936676-eea2-44bd-b17b-dc5e58fd000d/v_854.mp4/index-v1-a1.m3u8?x=EgvsRR7zZLXNoaz49v4D05BwcjHwPaNSOtkB9y98QGOIB_EyAhV_hc44Z4McLT_FTwzBWxpaK1WlNgSBkLd415LU1jRGz0yFNhciw_SDSwgj6OlAQCARiRIb9UU8XMh_dMXKr4KncBfgwnYLMOlUn6zfSa3ltot63vKiuw0CUpU1 : Server returned 4XX Client Error, but not one of 400,1,3,4

  


  please help me

  


• lld-link error compiling chromium with ffmpeg additional calls

  1er décembre 2020, par michal-b

  After adding some calls to ffmpeg from the ffmpeg_decoding_loop, I have errors when compiling on Windows (both directly on Windows and when cross-compiling from linux).
  
What I don't understand is that it works without an issue on linux/macos.

  


  I have multiple calls to ffmpeg code but let's boil it down to a representative example.

  


  I call this :

  


  const AVFilter *buffer_src = avfilter_get_by_name("buffer");


  


  On linux/macos : no problems.
  
On windows :

  


  lld-link: error: undefined symbol: avfilter_get_by_name
>>> referenced by .\..\..\media\ffmpeg\ffmpeg_decoding_loop.cc:111
>>>               obj/media/ffmpeg/ffmpeg/ffmpeg_decoding_loop.obj:(public: void __cdecl media::FFmpegDecodingLoop::InitFilterGraph(struct AVFrame *))
>>> referenced by .\..\..\media\ffmpeg\ffmpeg_decoding_loop.cc:112
>>>               obj/media/ffmpeg/ffmpeg/ffmpeg_decoding_loop.obj:(public: void __cdecl media::FFmpegDecodingLoop::InitFilterGraph(struct AVFrame *))



  


  Is there some additional configuration to be made on windows ?
  
I use visual studio 2019, windows 10.0.19041.0 sdk, llvm 10.0.0.