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• Undefined reference to 'av_register_all' [duplicate]

  4 avril 2018, par Hask

  This question already has an answer here :

  • What is an undefined reference/unresolved external symbol error and how do I fix it ?
    
    27 answers
    

  When I try to compile my cpp file in which the header files from ffmpeg are connected :

    #include 
  
    #include 
  
    extern "C"
  
    {
  
        #include "libavcodec/avcodec.h"
  
        #include "libavformat/avformat.h"
  
        #include "libswscale/swscale.h"
  
    }
  
  
  
    int main(int argc, char* argv[])
  
    {
  
        if(argc < 2)
  
        {
  
            printf("Usage: %s filename\n", argv[0]);
  
        }
  
        av_register_all();
  
        return 0;
  
    }

  When compiling with a simple command I get :

    D:\gcc\bin>g++ -o a a.cpp
  
    C:\users\root\Temp\ccC9UvT7.o:a.cpp:(.text+0x2a): undefined reference to 'av_register_all'
  
    collect2.exe: error: ld returned 1 exit status

  Using a more complex I get :

    D:\gcc\bin>g++ -o a a.cpp -lavutil -lavformat -lavcodec -lz
  
    d:/gcc/bin/../lib/gcc/mingw32/6.3.0/../../../../mingw32/bin/ld.exe: cannot -lavutil
  
    d:/gcc/bin/../lib/gcc/mingw32/6.3.0/../../../../mingw32/bin/ld.exe: cannot -lavformat
  
    d:/gcc/bin/../lib/gcc/mingw32/6.3.0/../../../../mingw32/bin/ld.exe: cannot -lavcodec
  
    d:/gcc/bin/../lib/gcc/mingw32/6.3.0/../../../../mingw32/bin/ld.exe: cannot -lz
  
    collect2.exe: error: ld returned 1 exit status

  How can I fix this ?

• C++ FFmpeg create mp4 file

  1er février 2021, par DDovzhenko

  I'm trying to create mp4 video file with FFmpeg and C++, but in result I receive broken file (windows player shows "Can't play ... 0xc00d36c4"). If I create .h264 file, it can be played with 'ffplay' and successfully converted to mp4 via CL.

  



  My code :

  



  int main() {
    char *filename = "tmp.mp4";
    AVOutputFormat *fmt;
    AVFormatContext *fctx;
    AVCodecContext *cctx;
    AVStream *st;

    av_register_all();
    avcodec_register_all();

    //auto detect the output format from the name
    fmt = av_guess_format(NULL, filename, NULL);
    if (!fmt) {
        cout << "Error av_guess_format()" << endl; system("pause"); exit(1);
    }

    if (avformat_alloc_output_context2(&fctx, fmt, NULL, filename) < 0) {
        cout << "Error avformat_alloc_output_context2()" << endl; system("pause"); exit(1);
    }


    //stream creation + parameters
    st = avformat_new_stream(fctx, 0);
    if (!st) {
        cout << "Error avformat_new_stream()" << endl; system("pause"); exit(1);
    }

    st->codecpar->codec_id = fmt->video_codec;
    st->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
    st->codecpar->width = 352;
    st->codecpar->height = 288;
    st->time_base.num = 1;
    st->time_base.den = 25;

    AVCodec *pCodec = avcodec_find_encoder(st->codecpar->codec_id);
    if (!pCodec) {
        cout << "Error avcodec_find_encoder()" << endl; system("pause"); exit(1);
    }

    cctx = avcodec_alloc_context3(pCodec);
    if (!cctx) {
        cout << "Error avcodec_alloc_context3()" << endl; system("pause"); exit(1);
    }

    avcodec_parameters_to_context(cctx, st->codecpar);
    cctx->bit_rate = 400000;
    cctx->width = 352;
    cctx->height = 288;
    cctx->time_base.num = 1;
    cctx->time_base.den = 25;
    cctx->gop_size = 12;
    cctx->pix_fmt = AV_PIX_FMT_YUV420P;
    if (st->codecpar->codec_id == AV_CODEC_ID_H264) {
        av_opt_set(cctx->priv_data, "preset", "ultrafast", 0);
    }
    if (fctx->oformat->flags & AVFMT_GLOBALHEADER) {
        cctx->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
    }
    avcodec_parameters_from_context(st->codecpar, cctx);

    av_dump_format(fctx, 0, filename, 1);

    //OPEN FILE + WRITE HEADER
    if (avcodec_open2(cctx, pCodec, NULL) < 0) {
        cout << "Error avcodec_open2()" << endl; system("pause"); exit(1);
    }
    if (!(fmt->flags & AVFMT_NOFILE)) {
        if (avio_open(&fctx->pb, filename, AVIO_FLAG_WRITE) < 0) {
            cout << "Error avio_open()" << endl; system("pause"); exit(1);
        }
    }
    if (avformat_write_header(fctx, NULL) < 0) {
        cout << "Error avformat_write_header()" << endl; system("pause"); exit(1);
    }


    //CREATE DUMMY VIDEO
    AVFrame *frame = av_frame_alloc();
    frame->format = cctx->pix_fmt;
    frame->width = cctx->width;
    frame->height = cctx->height;
    av_image_alloc(frame->data, frame->linesize, cctx->width, cctx->height, cctx->pix_fmt, 32);

    AVPacket pkt;
    double video_pts = 0;
    for (int i = 0; i < 50; i++) {
        video_pts = (double)cctx->time_base.num / cctx->time_base.den * 90 * i;

        for (int y = 0; y < cctx->height; y++) {
            for (int x = 0; x < cctx->width; x++) {
                frame->data[0][y * frame->linesize[0] + x] = x + y + i * 3;
                if (y < cctx->height / 2 && x < cctx->width / 2) {
                    /* Cb and Cr */
                    frame->data[1][y * frame->linesize[1] + x] = 128 + y + i * 2;
                    frame->data[2][y * frame->linesize[2] + x] = 64 + x + i * 5;
                }
            }
        }

        av_init_packet(&pkt);
        pkt.flags |= AV_PKT_FLAG_KEY;
        pkt.pts = frame->pts = video_pts;
        pkt.data = NULL;
        pkt.size = 0;
        pkt.stream_index = st->index;

        if (avcodec_send_frame(cctx, frame) < 0) {
            cout << "Error avcodec_send_frame()" << endl; system("pause"); exit(1);
        }
        if (avcodec_receive_packet(cctx, &pkt) == 0) {
            //cout << "Write frame " << to_string((int) pkt.pts) << endl;
            av_interleaved_write_frame(fctx, &pkt);
            av_packet_unref(&pkt);
        }
    }

    //DELAYED FRAMES
    for (;;) {
        avcodec_send_frame(cctx, NULL);
        if (avcodec_receive_packet(cctx, &pkt) == 0) {
            //cout << "-Write frame " << to_string((int)pkt.pts) << endl;
            av_interleaved_write_frame(fctx, &pkt);
            av_packet_unref(&pkt);
        }
        else {
            break;
        }
    }

    //FINISH
    av_write_trailer(fctx);
    if (!(fmt->flags & AVFMT_NOFILE)) {
        if (avio_close(fctx->pb) < 0) {
            cout << "Error avio_close()" << endl; system("pause"); exit(1);
        }
    }
    av_frame_free(&frame);
    avcodec_free_context(&cctx);
    avformat_free_context(fctx);

    system("pause");
    return 0;
}


  



  Output of program :

  



  Output #0, mp4, to 'tmp.mp4':
    Stream #0:0: Video: h264, yuv420p, 352x288, q=2-31, 400 kb/s, 25 tbn
[libx264 @ 0000021c4a995ba0] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2
[libx264 @ 0000021c4a995ba0] profile Constrained Baseline, level 2.0
[libx264 @ 0000021c4a995ba0] 264 - core 152 r2851 ba24899 - H.264/MPEG-4 AVC codec - Copyleft 2003-2017 - http://www.videolan.org/x264.html - options: cabac=0 ref=1 deblock=0:0:0 analyse=0:0 me=dia subme=0 psy=1 psy_rd=1.00:0.00 mixed_ref=0 me_range=16 chroma_me=1 trellis=0 8x8dct=0 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=0 threads=6 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=0 weightp=0 keyint=12 keyint_min=1 scenecut=0 intra_refresh=0 rc=abr mbtree=0 bitrate=400 ratetol=1.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=0
[libx264 @ 0000021c4a995ba0] frame I:5     Avg QP: 7.03  size:  9318
[libx264 @ 0000021c4a995ba0] frame P:45    Avg QP: 4.53  size:  4258
[libx264 @ 0000021c4a995ba0] mb I  I16..4: 100.0%  0.0%  0.0%
[libx264 @ 0000021c4a995ba0] mb P  I16..4:  0.0%  0.0%  0.0%  P16..4: 100.0%  0.0%  0.0%  0.0%  0.0%    skip: 0.0%
[libx264 @ 0000021c4a995ba0] final ratefactor: 9.11
[libx264 @ 0000021c4a995ba0] coded y,uvDC,uvAC intra: 18.9% 21.8% 14.5% inter: 7.8% 100.0% 15.5%
[libx264 @ 0000021c4a995ba0] i16 v,h,dc,p:  4%  5%  5% 86%
[libx264 @ 0000021c4a995ba0] i8c dc,h,v,p:  2%  9%  6% 82%
[libx264 @ 0000021c4a995ba0] kb/s:264.68


  



  If I will try to play mp4 file with 'ffplay' it prints :

  



  [mov,mp4,m4a,3gp,3g2,mj2 @ 00000000026bf900] Could not find codec parameters for stream 0 (Video: h264 (avc1 / 0x31637661), none, 352x288, 138953 kb/s): unspecified pixel format
[h264 @ 00000000006c6ae0] non-existing PPS 0 referenced
[h264 @ 00000000006c6ae0] decode_slice_header error
[h264 @ 00000000006c6ae0] no frame!


  



  I've spent a lot of time without success of finding issue, what could be the reason of it ?

  



  Thank for help !

  


• libavcodec/ffmpeg reports two channels when decoding, but segfaults when trying to access the second

  1er décembre 2017, par Astrognome

  I am attempting to decode an audio file into raw pcm data using FFMpeg’s libavcodec. I have the following code so far, but it segfaults when trying to access the second audio channel for some reason.

  #include 
  
  #include 
  
  #include <ao></ao>ao.h>
  
  #include 
  
  
  
  #include <libavutil></libavutil>opt.h>
  
  #include <libavcodec></libavcodec>avcodec.h>
  
  #include <libavformat></libavformat>avformat.h>
  
  #include <libswresample></libswresample>swresample.h>
  
  
  
  #define BUF_SIZE 4096
  
  
  
  
  
  #define AUDIO_INBUF_SIZE 20480
  
  #define AUDIO_REFILL_THRESH 4096
  
  
  
  int decode(AVCodecContext *dec_ctx, AVPacket *pkt, AVFrame *frame, uint8_t* out_data, int* index) {
  
  
  
      int i, ch;
  
      int ret, data_size;
  
  
  
      ret = avcodec_send_packet(dec_ctx, pkt);
  
      if (ret &lt; 0) {
  
          fprintf(stderr, "Error submitting packet to decoder\n");
  
          exit(1);
  
      }
  
  
  
      while (ret >= 0) {
  
          ret = avcodec_receive_frame(dec_ctx, frame);
  
          if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
  
              return 0;
  
          }
  
          else if (ret &lt; 0) {
  
              fprintf(stderr, "Error during decoding\n");
  
              exit(1);
  
          }
  
  
  
          data_size = av_get_bytes_per_sample(dec_ctx->sample_fmt);
  
          if (data_size &lt; 0) {
  
              fprintf(stderr, "Failed to calculate data size\n");
  
              exit(1);
  
          }
  
          for (i = 0; i &lt; frame->nb_samples; ++i)
  
              for (ch = 0; ch &lt; dec_ctx->channels; ++ch) {
  
  
  
                  //Things go wrong here...
  
                  memcpy(out_data + *index, frame->data[ch] + (data_size*i), data_size);
  
                  *index += data_size;
  
              }
  
      }
  
  
  
      return 0;
  
  }
  
  
  
  int decode_audio_file(const char* path, uint8_t* out_data, int size) {
  
      const AVCodec *codec;
  
      AVCodecContext *c = NULL;
  
      AVCodecParserContext *parser = NULL;
  
      int len, ret;
  
      FILE *f;
  
      uint8_t inbuf[AUDIO_INBUF_SIZE + AV_INPUT_BUFFER_PADDING_SIZE];
  
      uint8_t *data;
  
      size_t data_size;
  
      AVPacket *pkt;
  
      AVFrame *decoded_frame = NULL;
  
  
  
  
  
      avcodec_register_all();
  
      pkt = av_packet_alloc();
  
      codec = avcodec_find_decoder(AV_CODEC_ID_FLAC);
  
      if (!codec) {
  
          fprintf(stderr, "Codec not found!\n");
  
          return -1;
  
      }
  
  
  
      parser = av_parser_init(codec->id);
  
      if (!parser) {
  
          fprintf(stderr, "Parser not found!\n");
  
          return -1;
  
      }
  
  
  
      c = avcodec_alloc_context3(codec);
  
      if (!c) {
  
          fprintf(stderr, "Could not allocate audio context!\n");
  
          return -1;
  
      }
  
  
  
      if(avcodec_open2(c, codec, NULL) &lt; 0) {
  
          fprintf(stderr, "Could not open codec\n");
  
          exit(1);
  
      }
  
  
  
      f = fopen(path, "rb");
  
      if(!f) {
  
          fprintf(stderr, "Could not open %s\n", path);
  
          exit(1);
  
      }
  
  
  
      data = inbuf;
  
      data_size = fread(inbuf, 1, AUDIO_INBUF_SIZE, f);
  
  
  
      int index = 0;  
  
      while (data_size > 0) {
  
          if (!decoded_frame) {
  
              if (!(decoded_frame = av_frame_alloc())) {
  
                  fprintf(stderr, "Could not allocate audio frame\n");
  
                  exit(1);
  
              }
  
          }
  
  
  
          ret = av_parser_parse2(parser, c, &amp;pkt->data, &amp;pkt->size, data, data_size, AV_NOPTS_VALUE, AV_NOPTS_VALUE, 0);
  
          if (ret &lt; 0) {
  
              fprintf(stderr, "Error while parsing\n");
  
              exit(1);
  
          }
  
          data += ret;
  
          data_size -= ret;
  
  
  
          if (pkt->size)
  
              decode(c, pkt, decoded_frame, out_data, &amp;index);
  
          if (data_size &lt; AUDIO_REFILL_THRESH) {
  
              memmove(inbuf, data, data_size);
  
              data = inbuf;
  
              len = fread(data + data_size, 1, AUDIO_INBUF_SIZE - data_size, f);
  
              if (len > 0)
  
                  data_size += len;
  
          }
  
      }
  
      avcodec_free_context(&amp;c);
  
      av_parser_close(parser);
  
      av_frame_free(&amp;decoded_frame);
  
      av_packet_free(&amp;pkt);
  
  
  
      return 0;
  
  }
  
  
  
  
  
  int main(int argc, char **argv)
  
  {
  
      int bsize = 1024*1024*60;
  
      uint8_t* audio_buffer = calloc(bsize, sizeof(uint8_t));
  
      decode_audio_file("testsong.flac", audio_buffer, bsize);
  
  }

  Here is the offending line :

  memcpy(out_data + *index, frame->data[ch] + (data_size*i), data_size);

  If you access frame->data[0] it’s fine, but if you attempt to access frame->data[1] it segfaults. The context reports two channels and the file contains two channels (tried with several different tracks).
  But it gets even weirder. If I switch the offending line to

  memcpy(out_data + *index, frame->data[0] + (data_size*i*2 + ch), data_size);

  it will have the left channel with correct data and the right channel is white noise. This tells me (and I could be wrong) that the first channel actually contains 2 channels of audio interleaved, the actual left channel, plus a junk channel of white noise.
  I was wrong, I forgot to multiple ch by data_size. If the line is memcpy(out_data + *index, frame->data[0] + (data_size*i*2 + ch*data_size), data_size); things seem to work as expected. This all still seems very sketchy though so if anyone can thoroughly explain what’s happening here, that would be nice.

  I have been working off the decode_audio example available in the ffmpeg documentation here although modified slightly.

  This ALSO happens if I use the vanilla example with the only change being setting the codec to FLAC, so I assume it’s a bug in the library. In that case, how can I work around it.