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• avformat/m4vdec : Fix detection of raw MPEG-4 ES Studio

  29 avril 2018, par Michael Niedermayer

  avformat/m4vdec : Fix detection of raw MPEG-4 ES Studio
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavformat/m4vdec.c

• target_link_libraries in CMAKE using android studio 2.2.2

  22 novembre 2016, par fadi

  I am facing a weird issue and it’s difficult to know why because the compiler doesnt give any errors.

  I created a new project in android studio 2.2.2 with C++ support.
  I edited the .cpp file inside src/main/cpp and compiled the project to obtain (.so) file that i can use as a shared library. To this point everything works perfect.

  Here is where the problem occurs :

  I am trying to link prebuild shared libraries from ffmpeg. I have already build the libraries in .so format and all I need to do is link them to my .cpp file.

  To link the libraries, I opened the CMakeLists.txt inside android studio and told cmake to link those prebuild shared libraries using the following code :

  add_library(libavformat SHARED IMPORTED)

  set_target_properties(libavformat PROPERTIES IMPORTED_LOCATION  C:/Android  /SDK/MyProjects/ffmpeg_to_jpg/P3/app/src/main/jniLibs/libavformat-55.so)

  include_directories(src/main/cpp/include/)

  target_link_libraries(native-lib  libavformat)

  This code basically links libavformat to native-lib (which is created from my .cpp file)

  The linking process works fine, the reason is because the compiler doesn’t cry about any dependencies.

  However, my original shared library (native-lib) stops working, and by that I mean, I cannot call any functions from within it.

  If i remove the linking line

  target_link_libraries(native-lib  libavformat)

  The native-lib.so works fine and I can call any function from within that does not depend on libavformat.

  I am not sure what is going on, like I said the compiler doesnt issue any warnings or errors. it is almost like after the linking process the content of native-lib is overwritten by libavformat !!!!

  any ideas ?

• Compile FFmpeg Zeranoe Build with Visual Studio 2013

  19 janvier 2016, par mFeinstein

  I downloaded the most recent Zeranoe dev build here, included the header files to my code, placed extern "C" around the includes, since this is a C++ project and FFmpeg is a C library, and added the libs to Visual Studio as well, and I get this linker error :

  1>Camera.obj : error LNK2019 : unresolved external symbol _av_free referenced in function __catch$ ?NewFrameReceived@Camera@MicroDFV_Camera@@AAEXKKKGPAE@Z$0
  1>Camera.obj : error LNK2019 : unresolved external symbol _av_freep referenced in function __catch$ ?NewFrameReceived@Camera@MicroDFV_Camera@@AAEXKKKGPAE@Z$0
  1>Camera.obj : error LNK2019 : unresolved external symbol _av_frame_alloc referenced in function __catch$ ?NewFrameReceived@Camera@MicroDFV_Camera@@AAEXKKKGPAE@Z$0
  1>Camera.obj : error LNK2019 : unresolved external symbol _av_frame_free referenced in function __catch$ ?NewFrameReceived@Camera@MicroDFV_Camera@@AAEXKKKGPAE@Z$0
  1>Camera.obj : error LNK2019 : unresolved external symbol _avcodec_register_all referenced in function __catch$ ??0Camera@MicroDFV_Camera@@QAE@V ?$basic_string@DU ?$char_traits@D@std@@V ?$allocator@D@2@@std@@0PAX@Z$0
  1>Camera.obj : error LNK2019 : unresolved external symbol _avcodec_alloc_context3 referenced in function __catch$ ?NewFrameReceived@Camera@MicroDFV_Camera@@AAEXKKKGPAE@Z$0
  1>Camera.obj : error LNK2019 : unresolved external symbol _avcodec_open2 referenced in function __catch$ ?NewFrameReceived@Camera@MicroDFV_Camera@@AAEXKKKGPAE@Z$0
  1>Camera.obj : error LNK2019 : unresolved external symbol _avcodec_close referenced in function __catch$ ?NewFrameReceived@Camera@MicroDFV_Camera@@AAEXKKKGPAE@Z$0
  1>Camera.obj : error LNK2019 : unresolved external symbol _av_init_packet referenced in function __catch$ ?NewFrameReceived@Camera@MicroDFV_Camera@@AAEXKKKGPAE@Z$0
  1>Camera.obj : error LNK2019 : unresolved external symbol _av_packet_unref referenced in function __catch$ ?NewFrameReceived@Camera@MicroDFV_Camera@@AAEXKKKGPAE@Z$0
  1>Camera.obj : error LNK2019 : unresolved external symbol _avcodec_find_encoder referenced in function __catch$ ?NewFrameReceived@Camera@MicroDFV_Camera@@AAEXKKKGPAE@Z$0
  1>Camera.obj : error LNK2019 : unresolved external symbol _avcodec_encode_video2 referenced in function __catch$ ?NewFrameReceived@Camera@MicroDFV_Camera@@AAEXKKKGPAE@Z$0
  1>Camera.obj : error LNK2019 : unresolved external symbol _av_opt_set referenced in function __catch$ ?NewFrameReceived@Camera@MicroDFV_Camera@@AAEXKKKGPAE@Z$0
  1>Camera.obj : error LNK2019 : unresolved external symbol _av_image_alloc referenced in function __catch$ ?NewFrameReceived@Camera@MicroDFV_Camera@@AAEXKKKGPAE@Z$0
  1>M :\Desktop\OpenCVTest\Debug\OpenCVTest.exe : fatal error LNK1120 : 14 unresolved externals

  Searching here and on Google I found many recommendations, such as to add #pragma comment(lib,...), and that the libs are static, so their order is important, and none of this helps.

  So I scratched my head even more and realized that the Zeranoe build is made with MinGW-w64, so probably it won’t link with Visual Studio. I inspected the lib using dumpbin and the symbols on the libs don’t have the underscore, so I am pretty sure it won’t work.

  The other Zeranoe builds for Windows don’t have libs, they are just plain .exe or exe + .dll.

  Will I have to make my own VS2013 build of FFmpeg to link it, or is there some alternative way ?