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• doc/community : update the rules according to voting results

  6 novembre 2023, par Anton Khirnov

  doc/community : update the rules according to voting results
  Cf. :
  
  * http://lists.ffmpeg.org/pipermail/ffmpeg-devel/2023-October/316054.html
  
  * http://lists.ffmpeg.org/pipermail/ffmpeg-devel/2023-November/316618.html
  

  • [DH] doc/community.texi

• {OpenAL(+FFmpeg)} How to queue variable size buffer due to ogg format ?

  11 février 2014, par user3293833

  (First of all, I may feel sorry about my poor English as it's not my native language.)

  I use FFmpeg to decode some audio file and play it with OpenAL by "stream"(i.e."queue" and "unqueue" function of OpenAL).

  When I use my program to play .ogg file, I find that it has a variable nb_samples.(due to ogg has variable bit rate ??) There are 128 B, 512 B and 1024 B of nb_samples. As a results, I must call alDeleteBuffers and alGenBuffers before I use alBufferSamplesSOFT(similar to alBufferData) because it would fail to call alBufferSamplesSOFT without recreate the buffer.
  Notes : alBufferSamplesSOFT is provided by OpenAL Soft. You can just see it as alBufferData.

  Nevertheless, I think it's foolish and inefficient if I do this. Is there is some smart method ? I paste the part of code :

  while (av_read_frame(...) == 0){
  
    avcodec_decode_audio4(...);
  
    swr_convert(...);  // to convert PCM format from FLTP to FLT
  
    alDeleteBuffers(1, theBuffers[?]);
  
    alGenBuffers(1, theBuffers[?]);
  
    alBufferSamplesSOFT(...);  // put those data into OpenAL buffer
  
  }

  if I don't do this, It would failed to update the OpenAL buffer. Is there any method to create a variable size buffer or a big size buffer ? Or is there any method to change the size of buffer ?

  Thanks for you guys.

• Linking ffmpeg's libswresample from MacOS X 10.9 with C++

  8 janvier 2014, par user2530102

  I am trying to link to ffmpeg's libswresample from a C++ application. I have installed ffmpeg through Homebrew on Mac OS X 10.9. A simple test application links if it's compiled as C, but not if it's compiled as C++. Here is the sample code :

  #include 
  
  #include <libswresample></libswresample>swresample.h>
  
  
  
  int main()
  
  {
  
    swr_alloc();
  
    printf("Hello world\n");
  
    return 0;
  
  }

  When compiled as C with clang -I/usr/local/include -L/usr/local/lib -lswresample -o hello hello.c this creates the application as expected. When compiled with C++ using clang++ -I/usr/local/include -L/usr/local/lib -lswresample -o hello hello.cc it results in an error like the following :

  Undefined symbols for architecture x86_64:
  
    "swr_alloc()", referenced from:
  
        _main in hello-9jqOY4.o
  
  ld: symbol(s) not found for architecture x86_64
  
  clang: error: linker command failed with exit code 1 (use -v to see invocation)

  But running nm -a /usr/local/lib/libswresample.dylib includes 000000000000d8a9 T _swr_alloc and file /usr/local/lib/libswresample.dylib shows /usr/local/lib/libswresample.dylib: Mach-O 64-bit dynamically linked shared library x86_64 which I assume is expected. I have the same issue compiling the example with gcc/g++, and I also have the same issue when compiling ffmpeg with either clang or gcc, which leads me to think that there is just something I don't know about linking that should be obvious, but I haven't found any references suggesting that it should be different linking a library in C++ vs. C, and linking other libraries (sox, for example) presents no difficulties with an identical setup.

  I have seen posts related to linking issues in Mac OS X 10.9 because of the change from libstdc++ to libc++, but adding -stdlib=libstdc++ or -stdlib=libc++ seems to make no difference. It also makes no difference to add -mmacosx-version-min=10.6 or 10.9.

  Any help is greatly appreciated.