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• FFMPEG Undefined Reference to 'avcodoec_open2' in C++

  12 avril 2012, par ALM865

  I have an error when compiling one of my C++ programs after updating the FFMPEG library from 0.8 to 'ffmpeg version git-2012-04-12-277f20c'

  The error I get when I make my program is as follows :

  -------- begin --------
  
  Linking: Analysing_Server
  
  ./source/Encoding_Thread.o: In function `CEncoding_Thread::do_work()':
  
  /home/Analyser/source/Encoding_Thread.cpp:155: undefined reference to `avcodec_open2'
  
  collect2: ld returned 1 exit status
  
  make: *** [Analysing_Server] Error 1

  The relevant lines of my Make file is similar to running g++ as below :

  g++ test2.cpp -lavformat -lavcodec -lavutil -D__STDC_CONSTANT_MACROS

  A stripped down version of my relevant CPP code that throws the error is :

  #include 
  
  #include  
  
  
  
  #define LOG_OUT_STREAM_BUFF_SIZE  200000
  
  
  
  
  
  extern "C"  {
  
    /* The ffmpeg library is completely written in C, so we need to tell the C++ compiler that so it links correctly. */
  
    #include "stdint.h"
  
    #include "libavcodec/avcodec.h"
  
    #include "libavutil/mathematics.h"
  
    #include "libswscale/swscale.h"
  
    #include "libavfilter/avfilter.h"
  
  
  
    int avcodec_open2(AVCodecContext *avctx, AVCodec *codec, AVDictionary **options);
  
    int avcodec_encode_video2(AVCodecContext *avctx, AVPacket *avpkt, const AVFrame *frame, int *got_packet_ptr);
  
  }
  
  
  
  uint8_t m_outbuf[2][LOG_OUT_STREAM_BUFF_SIZE];
  
  unsigned int m_out_size[2];
  
  unsigned int m_OutBuffer_ID[2];
  
  unsigned int m_Buffer_ID; /* This is just a uniqueish stamp we give to each buffer so we can tell when they change.. */
  
  
  
  AVCodecContext * m_CodecContex;
  
  AVCodec * m_codec;
  
  struct SwsContext *m_img_convert_ctx;
  
  
  
  unsigned char* m_DataBuff;
  
  
  
  int Output_Width, Output_Height;
  
  int Output_Bitrate;
  
  
  
  
  
  int main(void) {
  
    //New version of FFMPEG calls this in avcodec_register_all
  
    //avcodec_init();
  
  
  
    /* register all the codecs */
  
    avcodec_register_all();
  
  
  
    /* Initalise the encoder */
  
    m_codec = avcodec_find_encoder(CODEC_ID_MP2);
  
  
  
    if (!m_codec) {
  
      printf("Encoding codec not found\n");
  
    }
  
  
  
    /* init the pointers.. */
  
    m_CodecContex = NULL;
  
  
  
    /* Default values.. */
  
    Output_Width = 1600;
  
    Output_Height = 1200;
  
    Output_Bitrate = 600000;
  
  
  
    /* Create/setup the Codec details.. */
  
    //Changed to work with new FFMPEG
  
    m_CodecContex = avcodec_alloc_context3(m_codec);
  
    avcodec_get_context_defaults3(m_CodecContex, m_codec);
  
  
  
    /* put sample parameters */
  
    m_CodecContex->bit_rate = Output_Bitrate;
  
    /* resolution must be a multiple of two */
  
  
  
    m_CodecContex->width = Output_Width;
  
    m_CodecContex->height = Output_Height;
  
    /* frames per second */
  
    m_CodecContex->time_base= (AVRational){1,25};
  
  
  
    m_CodecContex->gop_size = 10; /* emit one intra frame every ten frames */
  
    m_CodecContex->max_b_frames=1;
  
    m_CodecContex->pix_fmt = PIX_FMT_YUV420P; /* must be YUV for encoding.. */
  
  
  
  
  
    AVDictionary * RetunedAVDic;
  
  
  
    /* open it */
  
    //Changed to work with new FFMPEG
  
    if (avcodec_open2(m_CodecContex, m_codec, &RetunedAVDic) < 0) {
  
        printf("could not open codec");
  
    }
  
  }

  Unfortunately the example under 'doc/examples/decoding_encoding.c' that comes with FFMPEG no longer works because all the functions that it uses are now depreciated. My code is based on the example code and worked fine with FFMPEG 0.8 but does not compile with the newest version of FFMPEG. I have changed some of the depreciated functions to their newer versions but it still doesn't compile.

  Does anyone know why I am getting this error ? or does anyone have a link to an example like 'doc/examples/decoding_encoding.c' using the newest version of FFMPEG ?

• Ffprobe with print json doesn't print anything

  10 septembre 2012, par Richard Knop

  I am trying to get information about a movie (resolution, frame rate, bit rate, codecs, duration etc) in a human readable way. I found this commnad :

  ffprobe -v quiet -print_format json -show_format -show_streams somefile.asf

  In this Stack Overflow question : Get ffmpeg information in friendly way

  But it doesn't work for me. When I try it in a terminal, the output is empty :

  richard@richard-desktop:~/projects/hello-python$ ffprobe -v quiet -print_format json -show_format -show_streams tests/test_1.mpg 
  
  richard@richard-desktop:~/projects/hello-python$ 

• How to resize yuv420sp using FFmpeg

  27 juin 2012, par newentry

  How to resize yuv420sp data into some other resolution.I tried using ffmpeg sws_scale but no success.I tried by converting yuv420sp to yuv420p and then tried to resize yuv420p into RGB24 via sws_scale but the things it works when both src and destination width and height are same, but for different resolution didn't get correct rgb24. Can anyboody guide me with example code using c or if possible through Java itself .The final resized data must be in yuv420p.
  In my case i am trying to downsize the yuv420sp for eg 640*480 to 320*240 or 176*144.

  thanks,