Recherche avancée

Sur d’autres sites (7747)

• Can't link FFMPEG dynamically to VS 2019 project

  10 février 2021, par Maya Sela

  I downloaded the source code of FFMPEG 3.4.8 and built with MSVC as such :
  
After unzipping, open x86_x64 Cross Tools Command Prompt for VS 2019 and run msys2_shell.cmd. From there, run
  
./configure --toolchain=msvc --arch=x86_64 --enable-yasm --enable-asm --enable-shared --disable-static
and
make

  
I then created a new project in VS 2019.
  
In Properties > C/C++ > General > Additional Include Directories :
  
(Where all the headers are)

  


  E:\ffmpeg-3.4.8\libavutil
E:\ffmpeg-3.4.8\libavcodec
E:\ffmpeg-3.4.8\libavdevice
E:\ffmpeg-3.4.8\libavfilter
E:\ffmpeg-3.4.8\libavresample
E:\ffmpeg-3.4.8\libpostproc
E:\ffmpeg-3.4.8\libswscale
E:\ffmpeg-3.4.8\libswresample
E:\ffmpeg-3.4.8\libavformat


  


  In Properties > Linker > General > Additional Library Directories :
  
(Where the .lib files are)

  


  E:\ffmpeg-3.4.8\libavutil
E:\ffmpeg-3.4.8\libavcodec
E:\ffmpeg-3.4.8\libavdevice
E:\ffmpeg-3.4.8\libavfilter
E:\ffmpeg-3.4.8\libavresample
E:\ffmpeg-3.4.8\libpostproc
E:\ffmpeg-3.4.8\libswscale
E:\ffmpeg-3.4.8\libswresample
E:\ffmpeg-3.4.8\libavformat


  


  In Properties > Linker > Input > Additional Dependencies :

  


  avcodec.lib
avdevice.lib
avfilter.lib
avformat.lib
swresample.lib
swscale.lib


  


  For good measure, I copied the .dll files of each library to the Release folder of the project. There is one source file I am trying to build and run :

  


  &#xA;extern "C" {&#xA;#include <libavformat></libavformat>avformat.h>&#xA;}&#xA;&#xA;int main() {&#xA;    AVFormatContext* pFormatContext = avformat_alloc_context();&#xA;}&#xA;

  


  The result is as follows :

  


  1>------ Build started: Project: FFMPEG_example, Configuration: Release x64 ------
1>Source.cpp
1>Source.obj : error LNK2001: unresolved external symbol avformat_alloc_context
1>C:\Users\maya.s\source\repos\FFMPEG_example\x64\Release\FFMPEG_example.exe : fatal error LNK1120: 1 unresolved externals
1>Done building project "FFMPEG_example.vcxproj" -- FAILED.
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========


  


  Does anyone have an idea ?
  
Thanks !

  


• 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.

  


  


• 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.