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• Why do I get "error : invalid instruction mnemonic" when compiling FFmpeg for Android ?

  20 octobre 2018, par donturner

  I’m trying to compile FFmpeg 4.0 for Android using clang from the NDK (r18.1.5063045). My host architecture is Mac OS.

  Here’s my configure command :

  ./configure \
  
  --target-os=android \
  
  --arch=armv7-a \
  
  --enable-cross-compile \
  
  --cc=${ANDROID_NDK}/toolchains/llvm/prebuilt/darwin-x86_64/bin/clang \
  
  --enable-shared \
  
  --disable-static 

  This completes successfully. So I run make -j8 and get the following error :

  In file included from libavfilter/vf_mestimate.c:22:
  
  In file included from ./libavcodec/mathops.h:40:
  
  ./libavcodec/arm/mathops.h:90:26: error: invalid instruction mnemonic 'itt'
  
      "cmp   %1, %2  \n\t"
  
                       ^
  
  <inline asm="asm">:3:2: note: instantiated into assembly here
  
      itt   gt      
  
      ^~~
  
  </inline>

  Any idea what could be causing this ?

• How to link all object files in a folder when compiling C ?

  23 septembre 2018, par Truman Purnell

  So I have two folders :

  /ffmpeg
  /myproj

  Inside myproj I have a main method :

  #include 
  
  #include 
  
  #include "libavformat/avformat.h"
  
  #include "libavcodec/avcodec.h"
  
  
  
  int main(int argc, char *argv[])
  
  {
  
      AVFormatContext *pFormatCtx = NULL;
  
  
  
      if (avformat_open_input(&pFormatCtx, argv[1], NULL, 0) != 0)
  
          return -1;
  
  
  
      return EXIT_SUCCESS;
  
  }

  I am attempting to compile this file like so :

  cc main.c -I../ffmpeg ../ffmpeg/libavformat/utils.o

  and am receiving this error :

  "_ffio_set_buf_size", referenced from:
  
  _ff_configure_buffers_for_index in utils.o
  
  ld: symbol(s) not found for architecture x86_64

  I understand what it’s saying - I need to include the dependencies of utils.o, stored in file utils.d. But how do I do that on the command line ? There are tons, tons, tons of dependencies and I know people don’t type these manually !

• How to fix the error "duplicate symbol _LOG_BUFFER_LENGTH"

  25 mai 2019, par Florentin Lupascu

  I have a Unity project embedded into Swift 4 and when I build the project I get an error from a plugin named FFmpeg (used to record the screen) and the error is next :

  duplicate symbol _LOG_BUFFER_LENGTH in:
  
      /Users/developers/Library/Developer/Xcode/DerivedData/DemoApp-bszfgmzljpyourbdjoxkdabtilki/Build/Intermediates.noindex/DemoApp.build/Debug-iphoneos/DemoApp.build/Objects-normal/arm64/cmdutils.o
  
      /Users/developers/Library/Developer/Xcode/DerivedData/DemoApp-bszfgmzljpyourbdjoxkdabtilki/Build/Intermediates.noindex/DemoApp.build/Debug-iphoneos/DemoApp.build/Objects-normal/arm64/ffmpeg.o
  
  duplicate symbol _LOG_BUFFER_LENGTH in:
  
      /Users/developers/Library/Developer/Xcode/DerivedData/DemoApp-bszfgmzljpyourbdjoxkdabtilki/Build/Intermediates.noindex/DemoApp.build/Debug-iphoneos/DemoApp.build/Objects-normal/arm64/cmdutils.o
  
      /Users/developers/Library/Developer/Xcode/DerivedData/DemoApp-bszfgmzljpyourbdjoxkdabtilki/Build/Intermediates.noindex/DemoApp.build/Debug-iphoneos/DemoApp.build/Objects-normal/arm64/ffmpeg_wrapper.o
  
  duplicate symbol _LOG_BUFFER_LENGTH in:
  
      /Users/developers/Library/Developer/Xcode/DerivedData/DemoApp-bszfgmzljpyourbdjoxkdabtilki/Build/Intermediates.noindex/DemoApp.build/Debug-iphoneos/DemoApp.build/Objects-normal/arm64/cmdutils.o
  
      /Users/developers/Library/Developer/Xcode/DerivedData/DemoApp-bszfgmzljpyourbdjoxkdabtilki/Build/Intermediates.noindex/DemoApp.build/Debug-iphoneos/DemoApp.build/Objects-normal/arm64/intercept.o
  
  ld: 3 duplicate symbols for architecture arm64
  
  clang: error: linker command failed with exit code 1 (use -v to see invocation)

  I want to specify that if I export the project from Unity to Xcode without to embed it is working perfectly with this Plugin.
  What can be the problem with this error ?

  Until now I tried next thing to remove the error but none helped me :

  • I checked if I have "-ObjC" in Xcode in "Other Linker Flags" and I don’t have.
  • I removed a duplicate library (“libil2cpp.a”) from "Link Binary With Libraries" (XCODE)
  • I changed ’No Common Blocks’ from Yes to No (under Targets->Build Settings->Apple LLVM - Code Generation )

  At the end I have the same error.
  Here is a print screen :

  

  Thank you so much if you spend your time to read this and any idea will be helpful.