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• Android Live Streaming based on javaCV + FFMpeg crashes by adding red5 link

  1er octobre 2015, par user1914692

  The Android application code is from :
  Android Live Streaming courtesy of JavaCV and FFMPEG

  It streams the live camera video from the device.

  I follow one comment’s instruction (Yoshio Numai), to use Red5 as the stream server.
  By Red5 itself, I can successfully use simpleBroadcaster and simpleSubscriber to stream and display the live camera (from the computer) steam.

  In the MainActivity.java, I change the code as below :

  private String ffmpeg_link = "rtmp://192.168.1.105/oflaDemo/red5StreamDemo"; 

  And I can start the app in my Android device (Nexus 4).
  after click "start", the app crash, pops out a small window, saying :
  "Unfortunately, JavaCV 0.3 Stream Test has stopped. OK."

  Once I click the OK button, I find the app is still live in the task list.

  But the same thing will happen.
  What’s wrong here ?

• Cannot link with libswscale properly using cmake. Undefined symbols for architecture x86_64 : sws_getContext()

  8 novembre 2022, par J. Johnson

  I'm building a small project that will output video. I'm trying to link to libswscale to convert RGBA to YUV420, however, the linker ld cannot successfully find libswscale symbols.

  


  Undefined symbols for architecture x86_64:
  "sws_getContext(int, int, AVPixelFormat, int, int, AVPixelFormat, int, SwsFilter*, SwsFilter*, double const*)", referenced from:
      VideoWriter::writeFrame(std::__1::vector >) in video_writer.cpp.o


  


  The offending line of code is this.

  


  struct SwsContext *sws_ctx = sws_getContext(
    avCodecContext->width, avCodecContext->height, AV_PIX_FMT_RGBA,
    avCodecContext->width, avCodecContext->height, AV_PIX_FMT_YUV420P,
    SWS_BILINEAR, NULL, NULL, NULL);


  


  When I use -v on clang I see that the libswscale.dylib is being passed to ld. The dylib exists on the file system and is the same version as the library's header, as verified by otool.

  


   "/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ld" -demangle -lto_library /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/libLTO.dylib -no_deduplicate -dynamic -arch x86_64 -platform_version macos 10.15.0 11.1 -syslibroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.1.sdk -o bin/main -search_paths_first -headerpad_max_install_names CMakeFiles/main.dir/src/main.cpp.o CMakeFiles/main.dir/src/window.cpp.o CMakeFiles/main.dir/src/video_writer.cpp.o -rpath /usr/local/lib /usr/local/lib/libGLEW.2.2.0.dylib /usr/local/lib/libboost_program_options-mt.dylib -framework OpenGL /usr/local/Cellar/sdl2_image/2.6.2/lib/libSDL2_image.dylib /usr/local/lib/libSDL2.dylib /usr/local/Cellar/ffmpeg/5.1.2/lib/libavcodec.dylib /usr/local/Cellar/ffmpeg/5.1.2/lib/libswscale.dylib /usr/local/Cellar/ffmpeg/5.1.2/lib/libavutil.dylib -lc++ -lSystem /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/clang/12.0.0/lib/darwin/libclang_rt.osx.a -F/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk/System/Library/Frameworks


  


  This is my cmake file.

  


  cmake_minimum_required(VERSION 3.19.2)

project(FragTool VERSION 1.0)

set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${CMAKE_SOURCE_DIR}/cmake/")

# --- c++ build settings --- #
set(CMAKE_CXX_STANDARD 11)
set(CMAKE_CXX_STANDARD_REQUIRED True)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Weffc++ -O0")
set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)

set(CMAKE_BUILD_TYPE Debug)

# --- dependencies --- #
find_package(GLEW REQUIRED)
find_package(Boost 1.79.0 COMPONENTS program_options REQUIRED)

find_package(PkgConfig REQUIRED)
pkg_check_modules(LIBAV REQUIRED IMPORTED_TARGET
    libavcodec
    libswscale
    libavutil
)

pkg_check_modules(LIBSDL2 REQUIRED IMPORTED_TARGET
    sdl2
    sdl2_image
)

set(EXECUTABLE main)
add_executable(${EXECUTABLE} src/main.cpp)
target_sources(${EXECUTABLE} PRIVATE
    ${CMAKE_SOURCE_DIR}/src/window.cpp
    ${CMAKE_SOURCE_DIR}/src/video_writer.cpp
)

target_include_directories(${EXECUTABLE} PRIVATE ${CMAKE_SOURCE_DIR}/src)
target_include_directories(${EXECUTABLE} PRIVATE ${GLEW_INCLUDE_DIRS})

target_link_libraries(${EXECUTABLE} PRIVATE GLEW::glew)
target_link_libraries(${EXECUTABLE} PRIVATE ${Boost_LIBRARIES})
target_link_libraries(${EXECUTABLE} PRIVATE PkgConfig::LIBSDL2)
target_link_libraries(${EXECUTABLE} PRIVATE PkgConfig::LIBAV)


  


  I'm stumped as to what could be causing the linker to fail, given that it is being passed the libswscale dylib correctly as far as I can tell. I checked for any other versions of the dylib on the system that maybe are shadowing it, but didn't see any.

  


• 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.