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• I am really confused with this kind of compilation error( C ffmpeg Qt)

  31 octobre 2016, par David Tree

  I downloaded the latest ffmpeg source code and successfully installed it on Ubuntu
  But I failed to compile a simple demo.(I did included proper headers)

  Here are the error messages ,just to name a few :

  error: unknown type name 'AVFrame'
  
  
  
  error: 'NULL' undeclared (first use in this function)
  
  
  
  error: request for member 'streams' in something not a structure or union
  
  
  
  error: 'AVMEDIA_TYPE_VIDEO' undeclared (first use in this function)
  
  
  
  error: expected expression before ')' token

  Can you help me solve this problem ?

  Contents Added :

  e.g this is my includes

  extern "C"{
  
  #include <libavcodec></libavcodec>avcodec.h>
  
  #include <libavformat></libavformat>avformat.h>
  
  #include <libswscale></libswscale>swscale.h>
  
  #include <libavutil></libavutil>avutil.h>
  
  }
  
  
  
  int main(int argc, char *argv[]) {
  
  AVFormatContext *pFormatCtx;
  
  int i, videoStreamIdx;
  
  AVCodecContext *pCodecCtx;
  
  AVCodec *pCodec;
  
  AVFrame *pFrame;
  
  AVFrame *pFrameRGB;

  e.g AVFormatContext is declared in /usr/include/libavformat/avformat.h
  error message box shows Unknown type name AVFormatContext
  But How could it possibly be ?

• g++ Linking Error on Mac while compiling FFMPEG

  7 mai 2013, par Saptarshi Biswas

  g++ on Snow Leopard is throwing linking errors on the following piece of code

  test.cpp

  #include <iostream>
  
  using namespace std;
  
  #include <libavcodec></libavcodec>avcodec.h>    // required headers
  
  #include <libavformat></libavformat>avformat.h>
  
  int main(int argc, char**argv) {
  
      av_register_all();             // offending library call
  
      return 0;
  
  }
  
  </iostream>

  When I try to compile this using the following command

  g++ test.cpp -I/usr/local/include -L/usr/local/lib \
  
  -lavcodec -lavformat -lavutil -lz -lm -o test

  I get the error
  Undefined symbols :
  "av_register_all()", referenced from :
  _main in ccUD1ueX.o
  ld : symbol(s) not found
  collect2 : ld returned 1 exit status

  Interestingly, if I have an equivalent c code,
  test.c

  #include 
  
  #include <libavcodec></libavcodec>avcodec.h>
  
  #include <libavformat></libavformat>avformat.h>
  
  int main(int argc, char**argv) {
  
      av_register_all();
  
      return 0;
  
  }

  gcc compiles it just fine

  gcc test.c -I/usr/local/include -L/usr/local/lib \
  
  -lavcodec -lavformat -lavutil -lz -lm -o test

  I am using Mac OS X 10.6.5

  $ g++ --version
  
  i686-apple-darwin10-g++-4.2.1 (GCC) 4.2.1 (Apple Inc. build 5664)
  
  $ gcc --version
  
  i686-apple-darwin10-gcc-4.2.1 (GCC) 4.2.1 (Apple Inc. build 5664)

  FFMPEG's libavcodec, libavformat etc. are C libraries and I have built them on my machine like thus :

  ./configure --enable-gpl --enable-pthreads --enable-shared \
  
  --disable-doc --enable-libx264
  
  make && sudo make install

  As one would expect, libavformat indeed contains the symbol av_register_all

  $ nm /usr/local/lib/libavformat.a | grep av_register_all
  
  0000000000000000 T _av_register_all
  
  00000000000089b0 S _av_register_all.eh

  I am inclined to believe g++ and gcc have different views of the libraries on my machine. g++ is not able to pick up the right libraries. Any clue ?

• ffmpeg error using Fade Seconds [migrated]

  13 mai 2013, par Ben Humphreys

  I'm trying to fade a video clip in and out with a duration of a few seconds, and ffmpeg seemed like the best way.
  The documentation mentions a fade option, and I have it working with a time in frames, but I really want to be able to use seconds.

  Using the example from the docs, and adding the following to a working encode command :

  -vf "fade=t=in:st=5.5:d=0.5"

  I get :

  [fade @ 0x102f009a0] Option 'st' not found
  
  [AVFilterGraph @ 0x102f00d00] Error initializing filter 'fade' with args 't=in:st=5.5:d=0.5'

  I get the same error using the long argument start_time

  I have ffmpeg version 1.2 and libavfilter 3. 42.103 /  3. 42.103

  I would use frames to specify the fade time and duration, but I'm specifying clip length in seconds, and I have no idea how long the clip will be in frames. To specify fade out I need to know the length in frames, and then specify the start time as num_frames - fade_duration_in_frames.

  Has anyone else hit this problem ?