Recherche avancée

Sur d’autres sites (5491)

• LNK 2019 unresolved symbol - FFmpeg

  7 juin 2013, par Cristina1986

  I'm trying to use FFmpeg to open and read a video .avi
  I work on win7 x64 with Visual Studio 2010

  For now my code is very simple :

  #include "libavcodec/avcodec.h"
  
  #include "libavformat/avformat.h"
  
  #include "SDL.h"
  
  #include "SDL_mixer.h"
  
  
  
  
  
  int main (int argc, char *argv[]) {
  
  
  
  AVFormatContext *pFile_video;
  
  int             s, videoStream;
  
  AVCodecContext  *pCodecCtx;
  
  AVCodec         *pCodec;
  
  AVFrame         *pFrame; 
  
  AVFrame         *pFrameRGB;
  
  AVPacket        packet;
  
  int             frameFinished;
  
  int             numBytes;
  
  uint8_t         *buffer;
  
  
  
  av_register_all();
  
  
  
      if((avformat_open_input(&pFile_video, "AR.avi", NULL,NULL)!=0)) cout <<"cannot open video file"</if(av_find_stream_info(pFile_video) <0) cout <<"cannot retrive stream information"<nb_streams;s++){
  
          if((pFile_video->streams[s]->codec->codec_type) == AVMEDIA_TYPE_VIDEO) videoStream =s;
  
      }
  
      if(videoStream ==-1) cout <<"cannot open video stream"<code>

  I linked following .lib files :

  avcodec.lib
  
  avdevice.lib
  
  avfilter.lib
  
  avformat.lib
  
  avutil.lib
  
  postproc.lib
  
  swresample.lib
  
  swscale.lib

  but I get these errors :

  >MSVCRTD.lib(cinitexe.obj) : warning LNK4098: la libreria predefinita 'msvcrt.lib' è in conflitto con l'utilizzo di altre librerie; utilizzare /NODEFAULTLIB:libreria
  
  1>main_video_ffmpeg.obj : error LNK2019: riferimento al simbolo esterno "int __cdecl avformat_open_input(struct AVFormatContext * *,char const *,struct AVInputFormat *,struct AVDictionary * *)" (?avformat_open_input@@YAHPAPAUAVFormatContext@@PBDPAUAVInputFormat@@PAPAUAVDictionary@@@Z) non risolto nella funzione _SDL_main
  
  1>main_video_ffmpeg.obj : error LNK2019: riferimento al simbolo esterno "void __cdecl av_register_all(void)" (?av_register_all@@YAXXZ) non risolto nella funzione _SDL_main
  
  1>C:\Users\Cristina\Desktop\OpenCV\Progetti\MIEI_PROGETTI_Vs\video_ffmpeg\Debug\video_ffmpeg.exe : fatal error LNK1120: 2 esterni non risolti

  I think it is a linker error.. but I haven't other .lib file for FFmpeg library.

• Building FFMPEG library for iOS6.0 ARMv7 Processor

  15 août 2013, par Jimmy

  WARNING :

  I was just informed by another user that there are some legal issues revolving around using FFMPEG for iOS, leaving the link here http://multinc.com/2009/08/24/compatibility-between-the-iphone-app-store-and-the-lgpl/

  I cleaned up my question a little bit, when I wrote it the first time I was flustered. Now I can be more clear after taking a small break.

  Edit : learned that you have to build for ARMv7, ARMv7s and iOS6.0

  I'm trying to use the FFMPEG library in an XCode 4.5.1 project. And I'm trying to build it for ARMv7. What I'm looking for is the exact process, and some explanation. I understand that this is not a well documented problem. But I know that other pople have had the same problem as me.

  What I have been able to do.

  I have been able to build the library for testing.

  1) I have been able to clone ffmpeg. For beginners this will get you started by creating a directory with the ffmpeg source. (Kudos to the guys who wrote it)

  git clone git ://source.ffmpeg.org/ffmpeg.git ffmpeg

  2) I have been able to write a config file that doesn't have any errors. We will go back to this part later. This is the command I attach to ./configure

  ./configure
  —disable-doc
  —disable-ffmpeg
  —disable-ffplay
  —disable-ffserver
  —enable-cross-compile
  —arch=arm
  —target-os=darwin
  —cc=/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/usr/llvm-gcc-4.2/bin/arm-apple-darwin10-llvm-gcc-4.2

  —as='gas-preprocessor/gas-preprocessor.pl /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/usr/llvm-gcc-4.2/bin/arm-apple-darwin10-llvm-gcc-4.2'

  —sysroot=/applications/xcode.app/contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS6.0.sdk

  —cpu=cortex-a8
  —extra-ldflags='-arch=armv7 -isysroot /applications/xcode.app/contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS6.0.sdk'
  —enable-pic —disable-bzlib —disable-gpl —disable-shared —enable-static —disable-mmx —disable-debug —disable-neon —extra-cflags='-pipe -Os -gdwarf-2 -isysroot /applications/xcode.app/contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS5.1.sdk
  -m$thumb_opt :-no-thumb -mthumb-interwork'

  These are some things to note.

  • I had to download ( https://github.com/yuvi/gas-preprocessor ) copy the file gas-preprocessor.pl at /usr/local/bin. Set permissions to read write (777)
  • Make sure I'm using the right GCC compiler : /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/usr/llvm-gcc-4.2/bin/arm-apple-darwin10-llvm-gcc-4.2
  • Make sure I'm using the right SDK : /applications/xcode.app/contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS6.0.sdk
  • —extra-cflags="-arch armv7" causes : error : unrecognized command line option “-arch”

  Here in lies the problem.

  I can include the library like so

  libavcodec/avcodec.h

  But when I started to write the encoder. I received this warning, and countless errors.

  ignoring file /Users/Jimmy/Development/source.ffmpeg/Library/libavutil.a, file was built for archive which is not the architecture being linked (armv7s) : /Users/Jimmy/Development/source.ffmpeg/Library/libavutil.a

  That means that I didn't build the right binary.

  What I'm looking for is someone whose done it before, to walk all of us through the process of building FFMPEG for iOS6.0 and ARMv7 and the majority of things to look out for. Thanks a ton.

• Why does film/compositing use MJPEG rather than (say) H.264 ?

  3 juin 2016, par d3vid

  I have received a request to encode DPX files to MOV/MJPEG rather than MOV/H.264 (which ffmpeg picks by default if you convert to output.mov). These is to review compositing renders for animated film, so quality and color are critical.

  Comparing a sample "ideal" MOV to the current (H.264) output I can see :

  • resolution : the same
  • ColorSpace/Primaries : Rec609 (SD) versus Rec709 (HD) (better)
  • YUV : 4:2:0 versus 4:4:4 (better)
  • filesize : smaller

  The ffmpeg default seems to be better quality and result in a smaller filesize. Is there something I’m missing ?