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• Undefined reference, using FFMpeg-library (AvCodec) on Ubuntu, 64-bits system

  5 mai 2012, par Anders Branderud

  I am running the example code of the latest FFMpeg-library.
  I have inserted the example code into the file videofecencoder.c :

  /*
  
  * copyright (c) 2001 Fabrice Bellard
  
  *
  
  * This file is part of Libav.
  
  *
  
  * Libav is free software; you can redistribute it and/or
  
  * modify it under the terms of the GNU Lesser General Public
  
  * License as published by the Free Software Foundation; either
  
  * version 2.1 of the License, or (at your option) any later version.
  
  *
  
  * Libav is distributed in the hope that it will be useful,
  
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  
  * Lesser General Public License for more details.
  
  *
  
  * You should have received a copy of the GNU Lesser General Public
  
  * License along with Libav; if not, write to the Free Software
  
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  
  */
  
  #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
  
  
  
  
  
  #include 
  
  #include 
  
  #include 
  
  
  
  #ifdef HAVE_AV_CONFIG_H
  
  #undef HAVE_AV_CONFIG_H
  
  #endif
  
  
  
  #include "libavutil/imgutils.h"
  
  #include "libavutil/opt.h"
  
  #include "libavcodec/avcodec.h"
  
  #include "libavutil/mathematics.h"
  
  #include "libavutil/samplefmt.h"
  
  
  
  #define INBUF_SIZE 4096
  
  #define AUDIO_INBUF_SIZE 20480
  
  #define AUDIO_REFILL_THRESH 4096
  
  
  
  /*
  
  * Video encoding example
  
  */
  
  static void video_encode_example(const char *filename, int codec_id)
  
  {
  
     AVCodec *codec;
  
     AVCodecContext *c= NULL;
  
     int i, out_size, size, x, y, outbuf_size;
  
     FILE *f;
  
     AVFrame *picture;
  
     uint8_t *outbuf;
  
     int nrOfFramesPerSecond  =25;
  
     int nrOfSeconds =1;
  
  
  
  
  
     printf("Video encoding\n");
  
  
  
     /* find the mpeg1 video encoder */
  
     codec = avcodec_find_encoder((CodecID) codec_id);
  
     if (!codec) {
  
         fprintf(stderr, "codec not found\n");
  
         exit(1);
  
     }
  
  
  
     c = avcodec_alloc_context3(codec);
  
     picture= avcodec_alloc_frame();
  
  
  
     /* put sample parameters */
  
     c->bit_rate = 400000;
  
     /* resolution must be a multiple of two */
  
     c->width = 352;
  
     c->height = 288;
  
     /* frames per second */
  
     c->time_base= (AVRational){1,25};
  
     c->gop_size = 10; /* emit one intra frame every ten frames */
  
     c->max_b_frames=1;
  
     c->pix_fmt = PIX_FMT_YUV420P;
  
  
  
     if(codec_id == CODEC_ID_H264)
  
         av_opt_set(c->priv_data, "preset", "slow", 0);
  
  
  
     /* open it */
  
     if (avcodec_open2(c, codec, NULL) < 0) {
  
         fprintf(stderr, "could not open codec\n");
  
         exit(1);
  
     }
  
  
  
     f = fopen(filename, "wb");
  
     if (!f) {
  
         fprintf(stderr, "could not open %s\n", filename);
  
         exit(1);
  
     }
  
  
  
     /* alloc image and output buffer */
  
     outbuf_size = 100000;
  
     outbuf = (uint8_t*) malloc(outbuf_size);
  
  
  
     /* the image can be allocated by any means and av_image_alloc() is
  
      * just the most convenient way if av_malloc() is to be used */
  
     av_image_alloc(picture->data, picture->linesize,
  
                    c->width, c->height, c->pix_fmt, 1);
  
  
  
     /* encode 1 second of video */
  
     int nrOfFramesTotal = nrOfFramesPerSecond * nrOfSeconds;
  
  
  
     /* encode 1 second of video */
  
     for(i=0;i < nrOfFramesTotal; i++) {
  
         fflush(stdout);
  
         /* prepare a dummy image */
  
         /* Y */
  
         for(y=0;yheight;y++) {
  
             for(x=0;xwidth;x++) {
  
                 picture->data[0][y * picture->linesize[0] + x] = x + y + i * 3;
  
             }
  
         }
  
  
  
         /* Cb and Cr */
  
         for(y=0;yheight/2;y++) {
  
             for(x=0;xwidth/2;x++) {
  
                 picture->data[1][y * picture->linesize[1] + x] = 128 + y + i * 2;
  
                 picture->data[2][y * picture->linesize[2] + x] = 64 + x + i * 5;
  
             }
  
         }
  
  
  
         /* encode the image */
  
         out_size = avcodec_encode_video(c, outbuf, outbuf_size, picture);
  
         printf("encoding frame %3d (size=%5d)\n", i, out_size);
  
         fwrite(outbuf, 1, out_size, f);
  
     }
  
  
  
     /* get the delayed frames */
  
     for(; out_size; i++) {
  
         fflush(stdout);
  
  
  
         out_size = avcodec_encode_video(c, outbuf, outbuf_size, NULL);
  
         printf("write frame %3d (size=%5d)\n", i, out_size);
  
         fwrite(outbuf, 1, out_size, f);
  
     }
  
  
  
     /* add sequence end code to have a real mpeg file */
  
     outbuf[0] = 0x00;
  
     outbuf[1] = 0x00;
  
     outbuf[2] = 0x01;
  
     outbuf[3] = 0xb7;
  
     fwrite(outbuf, 1, 4, f);
  
     fclose(f);
  
     free(outbuf);
  
  
  
     avcodec_close(c);
  
     av_free(c);
  
     av_free(picture->data[0]);
  
     av_free(picture);
  
     printf("\n");
  
  }
  
  
  
  int main(int argc, char **argv)
  
  {
  
     const char *filename;
  
  
  
     /* register all the codecs */
  
     avcodec_register_all();
  
  
  
     if (argc <= 1) {
  
  
  
         video_encode_example("/grb_1.mpg", CODEC_ID_MPEG1VIDEO);
  
     } else {
  
         filename = argv[1];
  
     }
  
  
  
  
  
     return 0;
  
  }

  When I run gcc videofecencoder.cc -lavcodec I get the following error messages :

  /tmp/ccJg8IDy.o: In function `video_encode_example(char const*, int)':
  
  videofecencoder.cc:(.text+0x35): undefined reference to `avcodec_find_encoder(CodecID)'
  
  videofecencoder.cc:(.text+0x74): undefined reference to `avcodec_alloc_context3(AVCodec*)'
  
  videofecencoder.cc:(.text+0x7d): undefined reference to `avcodec_alloc_frame()'
  
  videofecencoder.cc:(.text+0x113): undefined reference to `av_opt_set(void*, char const*, char const*, int)'
  
  videofecencoder.cc:(.text+0x12b): undefined reference to `avcodec_open2(AVCodecContext*, AVCodec*, AVDictionary**)'
  
  videofecencoder.cc:(.text+0x1f0): undefined reference to `av_image_alloc(unsigned char**, int*, int, int, PixelFormat, int)'
  
  videofecencoder.cc:(.text+0x35c): undefined reference to `avcodec_encode_video(AVCodecContext*, unsigned char*, int, AVFrame const*)'
  
  videofecencoder.cc:(.text+0x3cf): undefined reference to `avcodec_encode_video(AVCodecContext*, unsigned char*, int, AVFrame const*)'
  
  videofecencoder.cc:(.text+0x47c): undefined reference to `avcodec_close(AVCodecContext*)'
  
  videofecencoder.cc:(.text+0x488): undefined reference to `av_free(void*)'
  
  videofecencoder.cc:(.text+0x497): undefined reference to `av_free(void*)'
  
  videofecencoder.cc:(.text+0x4a3): undefined reference to `av_free(void*)'
  
  /tmp/ccJg8IDy.o: In function `main':
  
  videofecencoder.cc:(.text+0x4c3): undefined reference to `avcodec_register_all()'
  
  collect2: ld returnerade avslutningsstatus 1

  The command nm libavcodec.a | grep avcodec_find results in :

  00000000000008e0 T avcodec_find_best_pix_fmt
  
  0000000000000740 T avcodec_find_best_pix_fmt2
  
                   U avcodec_find_encoder
  
  0000000000002ca0 T avcodec_find_decoder
  
  0000000000002cf0 T avcodec_find_decoder_by_name
  
  0000000000002bd0 T avcodec_find_encoder
  
  0000000000002c30 T avcodec_find_encoder_by_name

  I also have another similar error with another library :
  Undefined reference despite linking in OpenFEC-library

  My system : Ubuntu 11, 64-bits machine

  My next step is to try to compile it on VirtualBox with Ubuntu 32 bits (running on a Windows-OS).