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• Compiling ffmpeg for use in Android (ndk) for x86 architecture

  26 septembre 2012, par Ankur22

  I am trying to compile ffmpeg for Android but for the x86 architecture. I've successfully compiled an arm .so and it all works, and I though that by replacing arm with x86 in the relevant places within the build script would have done the trick. Unfortunately that's not the case and I get some strange things occurring.

  First I get this while it's compiling ffmpeg :

  /home/ankur/android-ndk-r8/platforms/android-8/arch-arm//usr/include/strings.h:49: warning: redundant redeclaration of 'index'

  Notice the arch-arm instead of arch-x86. Finally I get this :

  /home/ankur/android-ndk-r8/toolchains/x86-4.4.3/prebuilt/linux-x86/bin/i686-android-linux-ld: libavcodec/libavcodec.a(4xm.o): Relocations in generic ELF (EM: 40)
  
  /home/ankur/android-ndk-r8/toolchains/x86-4.4.3/prebuilt/linux-x86/bin/i686-android-linux-ld: libavcodec/libavcodec.a(4xm.o): Relocations in generic ELF (EM: 40)
  
  /home/ankur/android-ndk-r8/toolchains/x86-4.4.3/prebuilt/linux-x86/bin/i686-android-linux-ld: libavcodec/libavcodec.a(4xm.o): Relocations in generic ELF (EM: 40)
  
  libavcodec/libavcodec.a(4xm.o): could not read symbols: File in wrong format

  The build script I've created looks like this :

  #!/bin/bash
  
  
  
  NDK=~/android-ndk-r8
  
  PLATFORM=$NDK/platforms/android-8/arch-x86/
  
  PREBUILT=$NDK/toolchains/x86-4.4.3/prebuilt/linux-x86
  
  function build_one_r8
  
  {
  
  ./configure \
  
      --disable-shared \
  
      --enable-static \
  
      --enable-gpl \
  
      --enable-version3 \
  
      --enable-nonfree \
  
      --disable-doc \
  
      --disable-ffmpeg \
  
      --disable-ffplay \
  
      --disable-ffprobe \
  
      --disable-ffserver \
  
      --disable-avdevice \
  
      --disable-avfilter \
  
      --disable-postproc \
  
      --enable-small \
  
      --cross-prefix=$PREBUILT/bin/i686-android-linux- \
  
      --enable-cross-compile \
  
      --target-os=linux \
  
      --extra-cflags="-I$PLATFORM/usr/include" \
  
      --arch=x86 \
  
      --disable-symver \
  
      --disable-debug \
  
      --disable-stripping \
  
      $ADDITIONAL_CONFIGURE_FLAG
  
  sed -i 's/HAVE_LRINT 0/HAVE_LRINT 1/g' config.h
  
  sed -i 's/HAVE_LRINTF 0/HAVE_LRINTF 1/g' config.h
  
  sed -i 's/HAVE_ROUND 0/HAVE_ROUND 1/g' config.h
  
  sed -i 's/HAVE_ROUNDF 0/HAVE_ROUNDF 1/g' config.h
  
  sed -i 's/HAVE_TRUNC 0/HAVE_TRUNC 1/g' config.h
  
  sed -i 's/HAVE_TRUNCF 0/HAVE_TRUNCF 1/g' config.h
  
  make clean
  
  make  -j4 install
  
  $PREBUILT/bin/i686-android-linux-ar d libavcodec/libavcodec.a inverse.o
  
  $PREBUILT/bin/i686-android-linux-ld -rpath-link=$PLATFORM/usr/lib -L$PLATFORM/usr/lib  -soname libffmpeg.so -shared -nostdlib  -z,noexecstack -Bsymbolic --whole-archive --no-undefined -o $PREFIX/libffmpeg.so libavcodec/libavcodec.a libavformat/libavformat.a libavutil/libavutil.a libswscale/libswscale.a -lc -lm -lz -ldl -llog  --warn-once  --dynamic-linker=/system/bin/linker $PREBUILT/lib/gcc/i686-android-linux/4.4.3/libgcc.a
  
  }
  
  function build_one_r8_2
  
  {
  
  $PREBUILT/bin/i686-android-linux-ar d libavcodec/libavcodec.a inverse.o
  
  $PREBUILT/bin/i686-android-linux-ld -rpath-link=$PLATFORM/usr/lib -L$PLATFORM/usr/lib  -soname libffmpeg.so -shared -nostdlib  -z,noexecstack -Bsymbolic --whole-archive --no-undefined -o $PREFIX/libffmpeg.so libavcodec/libavcodec.a libavformat/libavformat.a libavutil/libavutil.a libswscale/libswscale.a -lc -lm -lz -ldl -llog  --warn-once  --dynamic-linker=/system/bin/linker $PREBUILT/lib/gcc/i686-android-linux/4.4.3/libgcc.a
  
  }
  
  #x86
  
  CPU=x86
  
  OPTIMIZE_CFLAGS="-march=$CPU "
  
  PREFIX=./android/$CPU
  
  ADDITIONAL_CONFIGURE_FLAG=
  
  build_one_r8

  I hope I'm doing something wrong rather than this not being possible.

  Thanks !

• Fundamentally, what exactly is a codec ?

  22 décembre 2013, par Bitwize

  I really hope I don't get down-voted for this, but this is something I have wondered for quite a while now.

  I have been reading through a series of articles describing what codecs are/what they do, and the difference between them and Containers, but where I become confused is in what a codec is fundamentally.

  Is a codec an executable binary/library that handles the compression/decompression of files for a specific program/API ?
  Or is it a form of library for programmers to use in order to handle these containers ?

  Reading various answers around the web it sounds as though it's almost treated as both, which is a little confusing.
  I'm hoping someone here can help clarify.

  Thanks !

• runtime error when linking ffmpeg libraries in qt creator

  6 juillet 2012, par dxthegreat

  I'm quite new around here but i hear that if you want a question answered, stackoverflow is the place to ask it >.<. So i hope that my question isn't too trivial that everyone will get annoyed at my lack of research (I've tried googling for two days already D= no progress !)
  I've also asked this question in the Qt forums, but i figured i'd ask here too.

  so...

  For the last few days I’ve been fiddling around with opengl and the like, trying to write a video player.

  However, when i try to import the ffmpeg libraries (avcodec, avformat, avutils etc), an error occurs on runtime (the program compiles fine). When compiled and run in debug mode, the error message gives me only a memory address and error code 135 (DLL not found).

  This error occurs when i include a function from those libraries in my code (e.g. av_register_all()) and it occurs regardless of whether the function is actually called.

  So i’m thinking that I’m doing something wrong when linking these libraries.
  I’m currently using :
  Windows vista (32bit),
  Qt creator 2.4.1 based on Qt 4.7.4 (32bit),
  Zeranoe’s FFmpeg build git-3233ad4 (2012-06-30)

  My .pro file consists of :

  QT       += core gui opengl
  
  
  
  TARGET = test
  
  TEMPLATE = app
  
  
  
  
  
  SOURCES += main.cpp\
  
          mainwindow.cpp \
  
      glwidget.cpp
  
  
  
  HEADERS += mainwindow.h \
  
      glwidget.h \
  
  
  
  FORMS    += mainwindow.ui
  
  
  
  
  
  LIBS += -L"$$_PRO_FILE_PWD_/libraries/ffmpeg/libs/" -lavcodec -lavformat -lavutil
  
  INCLUDEPATH += libraries/ffmpeg/includes

  I’ve tried many variations to the LIBS += line and checked my filepath many times. However, the DLL not found error occurs in all of these variations =(.

  Is there something I’m forgetting when doing these includes ?

  Thanks in advance >.<,
  (young and naive) aspiring dev