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• Which audio codecs are supported for HLS ?

  22 janvier 2017, par Jofsey

  Does HLS protocol specify audio codec ? If it does, which are supported ?

  I’ve tried to search, but found different lists :

  MP3, HE-AAC or AC-3

  according to wikipedia

  AAC, AAC-LC, HE-AAC (accPlus) v1 & v2, MP3

  according to this

  AAC-LC, HE-AACV1-2, AC-3, and EC-3

  according to FairPlay overview (which is subset of HLS)

• FFmpeg/GStreamer - Extract alpha channel from HEVC (H.265) elementary stream

  10 mars 2021, par Jonathan Ellis

  I have produced an HEVC (H.265) elementary stream which contains alpha (produced from Apple VideoToolbox framework), from which I would like to extract the alpha channel for further processing.

  


  I'd like to process the alpha in either one of these two ways :-

  


  (a) A series of grayscale PNG/JPEG images, with the alpha channel of each frame

  


  or

  


  (b) A series of PNGs with alpha with the RGB and Alpha composited in a single, semi-transparent image

  


  How can I achieve either of these with FFmpeg/GStreamer ?

  


• Why does ffmpeg cmake external project is not working

  24 mars 2019, par bottega

  I’m trying to compile ffmpeg with h264 support as an external cmake project. But after compile it, I’m getting libavcodec reference errors.

  The compile problem is occurring on Ubuntu 18.04 machine. I have installed all dependencies for ffmpeg and also libx264-dev.

  Cmake external project

  set( proj ffmpeg )
  
  set( SHARED_FFMPEG )
  
  
  
  
  
  set(BASIC
  
          --extra-ldflags=-L/usr/local/lib
  
          --extra-cflags=-I/usr/local/include
  
          --enable-gpl
  
          --enable-libx264)
  
  
  
  
  
  option( FFMPEG_GPL "Use a GPL version of FFMPEG" OFF )
  
  
  
  set(FFMPEG_INSTALL_DIR  ${CMAKE_BINARY_DIR}/INSTALL )
  
  
  
  ExternalProject_Add(${proj}
  
          # Set up dirs
  
          SOURCE_DIR ${CMAKE_BINARY_DIR}/${proj}
  
          INSTALL_DIR ${FFMPEG_INSTALL_DIR}
  
          # get the project
  
          GIT_REPOSITORY "https://github.com/FFmpeg/FFmpeg.git"
  
          GIT_TAG "n3.2.13"
  
  
  
          # Build the project
  
          BUILD_IN_SOURCE 1
  
  
  
          # Configure step
  
          # DO STH FOR THE ARCHITECTURE...
  
          CONFIGURE_COMMAND /configure --prefix=${FFMPEG_INSTALL_DIR} ${SHARED_FFMPEG} ${FFMPEG_GPL_FLAG} ${BASIC}
  
  
  
          #  BUILD_COMMAND ${CMAKE_MAKE_PROGRAM} -j${NProcessors}
  
          )
  
  
  
  # define the library suffix
  
  if( SUPER_SHARED_LIBS )
  
      if( APPLE )
  
          set(LIBRARY_SUFFIX .dylib)
  
      else( APPLE )
  
          set(LIBRARY_SUFFIX .so)
  
      endif( APPLE )
  
  else( SUPER_SHARED_LIBS )
  
      set(LIBRARY_SUFFIX .a)
  
  endif( SUPER_SHARED_LIBS )
  
  
  
  # ADD DIRECTORIES FOR DEPENDENCIES IN Main/CMakeLists.txt
  
  set( FFMPEG_LIBRARYS libavcodec.a
  
          libavformat.a
  
          libavutil.a
  
          libswscale.a
  
          )
  
  
  
  include_directories(${FFMPEG_INSTALL_DIR}/include)
  
  
  
  set(FFMPEG_LIBRARY_DIRS ${FFMPEG_INSTALL_DIR}/lib/)
  
  link_directories(${FFMPEG_LIBRARY_DIRS})

  C++ Where I used the library

  extern "C" {
  
  #include 
  
  #include 
  
  #include 
  
  
  
  #include "libavcodec/avcodec.h"
  
  #include "libavformat/avformat.h"
  
  #include "libavutil/mathematics.h"
  
  #include "libswscale/swscale.h"
  
  
  
  #define INBUF_SIZE 4096
  
  #define AUDIO_INBUF_SIZE 20480
  
  #define AUDIO_REFILL_THRESH 4096
  
  }
  
  
  
  ...
  
  
  
   fReceiveBuffer = new u_int8_t[DUMMY_SINK_RECEIVE_BUFFER_SIZE];
  
      fReceiveBufferAV = new u_int8_t[DUMMY_SINK_RECEIVE_BUFFER_SIZE+4];
  
      fReceiveBufferAV[0] = 0;
  
      fReceiveBufferAV[1] = 0;
  
      fReceiveBufferAV[2] = 0;
  
      fReceiveBufferAV[3] = 1;
  
  
  
  
  
      av_init_packet(&avpkt);
  
      avpkt.flags |= AV_PKT_FLAG_KEY;
  
      avpkt.pts = avpkt.dts = 0;
  
  
  
      av_init_packet(&avpkt);
  
      avpkt.flags |= AV_PKT_FLAG_KEY;
  
      avpkt.pts = avpkt.dts = 0;
  
  
  
      /* set end of buffer to 0 (this ensures that no overreading happens for damaged mpeg streams) */
  
      memset(inbuf + INBUF_SIZE, 0, FF_INPUT_BUFFER_PADDING_SIZE);
  
  
  
      //codec = avcodec_find_decoder(CODEC_ID_MPEG1VIDEO);
  
      codec = avcodec_find_decoder(AV_CODEC_ID_H264);
  
  
  
  ...

  Error :

  [100%] Linking CXX executable ../../bin/awesom-o
  
  /home/tiburcio/CLionProjects/awesom-o/cmake-build-debug/INSTALL/lib/libavcodec.a(libx264.o): In function `X264_frame':
  
  /home/tiburcio/CLionProjects/awesom-o/cmake-build-debug/ffmpeg/libavcodec/libx264.c:280: undefined reference to `x264_picture_init'
  
  /home/tiburcio/CLionProjects/awesom-o/cmake-build-debug/INSTALL/lib/libavcodec.a(libx264.o): In function `reconfig_encoder':
  
  /home/tiburcio/CLionProjects/awesom-o/cmake-build-debug/ffmpeg/libavcodec/libx264.c:266: undefined reference to `x264_encoder_reconfig'
  
  /home/tiburcio/CLionProjects/awesom-o/cmake-build-debug/INSTALL/lib/libavcodec.a(libx264.o): In function `X264_frame':
  
  /home/tiburcio/CLionProjects/awesom-o/cmake-build-debug/ffmpeg/libavcodec/libx264.c:340: undefined reference to `x264_encoder_encode'