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• RTP H263 frames to FFMPEG

  25 août 2011, par Pierluigi Cifani

  I've been trying to develop an RTP demuxed based on RFC 2190 to pass to the FFMPEG (libavcodec) H263 packets in Mode-A.

  However I can't seem to make the FFMPEG happy with the I-frames I am feeding it with. With fragmented frames (such as a large I-frame) I am rebuilding the whole frame following RFC 2190 and the "Marker" rules and passing it to the Libavcodec layer. However video looks buggy and it looks that I have to add some kind of header to the beginning of each frame before passing it to the Libavcodec layer. Errors like this are coming out all the time :

  illegal dc 128 at 0 3
  
  illegal ac vlc code at 0x3
  
  Error at MB: 69
  
  illegal ac vlc code at 4x15
  
  Error at MB: 349
  
  concealing 379 DC, 379 AC, 379 MV errors

  I have previously built an H264 over RTP demuxer and I had to add 0x00 0x00 0x00 0x01 0x21 header to every fragment of I Frame in order for it to be decoded correctly. But I can't find anywhere documentation on how to do this with H263.

  Maybe you could lend me a hand ?

  Cheers and thanks a lot

• UWP C# and Windows Runtime Component C++ Permission Denied error when opening file

  29 décembre 2020, par Surya Solanki

  I have developed a UWP app in C# which contains a Windows Runtime Component C++ project. the app allows the user to choose an mp4 file and passes this file to the c++ code, which then utilizes ffmpeg libraries to retrieve the presentation time stamps of a video file and output them to a file.

  


  the issue i'm facing is that the c++ code is not able to open the mp4 file when using the avformat_open_input function :

  


  int PTSExtraction::parse_file(Platform::String^ filename)
{
    int ret = 0;
    AVPacket pkt = { 0 };


    std::wstring fileNameW(filename->Begin());
    std::string fileNameA(fileNameW.begin(), fileNameW.end());
    const wchar_t* w_chars = fileNameW.c_str();
    src_filename = fileNameA.c_str(); 

    if (avformat_open_input(&fmt_ctx, src_filename, NULL, NULL) < 0) {
        fprintf(stderr, "Could not open source file %s\n", src_filename);
        return 1; 
    }
    // rest of code 
}


  


  the error received by avformat_open_input is Permission Denied. I cannot even open a random text file in this function by doing :

  


  ofstream output; 
output.open("output.txt");


  


  I realize there are file system permissions that are blocking the C++ component of my uwp app from opening files. here are the things i have tried so far :

  


  

  • i have enabled broadFileSystemAccess in the Package.appxmanifest (https://blogs.windows.com/windowsdeveloper/2018/05/18/console-uwp-applications-and-file-system-access/) - in the Capabilities section of the Package.appxmanifest file I've allowed access to Location, Pictures Library, and Videos Library.

  


  • I've checked the File System Privacy Settings on my computer and enabled my app to access the File System.

  


  • I've tried moving the mp4 file to various locations (Documents, Pictures Library, Videos Library) to see if the C++ component has access to these locations.

  


  • I've tried the solution from this post : Qt WinRT App cannot access file permission denied.

  


  


  None of these allow the C++ component to open any files. i would really appreciate if anyone has a solution for this problem.

  


• FFmpeg has text relocation's.This is wasting memory and prevents security hardening

  6 février 2018, par Sagar Hudge

  I am getting following exception on video trimming.

  video path : /storage/emulated/0/Pictures/Instagram/Fast & Furious 7 - Get Low Extended Version Video.mp4

  I have found the issue ,it is causing due to the file name having spaces in between them you can check in above mentioned path and in exception.

  after changing file name its working but changing name of every file from device its not the right way so how can I solve this exception

  FAILED with output : WARNING: linker: /data/user/0/com.example.SeekBarActivity/files/ffmpeg 
  
  has text relocations. This is wasting memory and prevents security hardening.
  
  Please fix. ffmpeg version n2.4.2 Copyright (c) 2000-2014 the FFmpeg developers
  
  
  
  built on Oct  7 2014 15:08:46 with gcc 4.8 (GCC)
  
  configuration: --target-os=linux --cross-prefix=/home/sb/Source-Code/ffmpeg-
  
  android/toolchain-android/bin/arm-linux-androideabi- --arch=arm --
  
  cpu=cortex-a8 --enable-runtime-cpudetect --sysroot=/home/sb/Source-
  
  Code/ffmpeg-android/toolchain-android/sysroot --enable-pic --enable-libx264 
  
  --enable-libass --enable-libfreetype --enable-libfribidi --enable-fontconfig 
  
  --enable-pthreads --disable-debug --disable-ffserver --enable-version3 --
  
  enable-hardcoded-tables --disable-ffplay --disable-ffprobe --enable-gpl --
  
  enable-yasm --disable-doc --disable-shared --enable-static --pkg-
  
  config=/home/sb/Source-Code/ffmpeg-android/ffmpeg-pkg-config --
  
  prefix=/home/sb/Source-Code/ffmpeg-android/build/armeabi-v7a-neon --extra-
  
  cflags='-I/home/sb/Source-Code/ffmpeg-android/toolchain-android/include -
  
  U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 -fno-strict-overflow -fstack-protector-
  
  all -mfpu=neon' --extra-ldflags='-L/home/sb/Source-Code/ffmpeg-
  
   android/toolchain-android/lib -Wl,-z,relro -Wl,-z,now -pie' --extra-libs='-
  
   lpng -lexpat -lm' --extra-cxxflags=
  
    libavutil      54.  7.100 / 54.  7.100
  
    libavcodec     56.  1.100 / 56.  1.100
  
    libavformat    56.  4.101 / 56.  4.101
  
    libavdevice    56.  0.100 / 56.  0.100
  
    libavfilter     5.  1.100 /  5.  1.100
  
    libswscale      3.  0.100 /  3.  0.100
  
    libswresample   1.  1.100 /  1.  1.100
  
    libpostproc    53.  0.100 / 53.  0.100
  
    /storage/emulated/0/Pictures/Instagram/Fast: No such file or directory