C++ 未定义参考，在Ubuntu上使用FFMpeg库（AvCodec），64位系统

我正在运行最新的FFMpeg库的示例代码。 我已将示例代码插入文件

videofeccoder.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 <stdlib.h>
#include <stdio.h>
#include <string.h>

#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;y<c->height;y++) {
           for(x=0;x<c->width;x++) {
               picture->data[0][y * picture->linesize[0] + x] = x + y + i * 3;
           }
       }

       /* Cb and Cr */
       for(y=0;y<c->height/2;y++) {
           for(x=0;x<c->width/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;
}

命令

nm libavcodec.a | grep avcodec_find

产生以下结果：

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

我还有另一个库的类似错误：

我的系统：Ubuntu 11，64位机器

我的下一步是尝试使用32位Ubuntu（在Windows操作系统上运行）在VirtualBox上编译它。

我（终于！！）参考了FFMpeg邮件列表中的解决方案：

---

p>引用：“FFMPEG是一个纯C项目，所以使用C++应用程序中的库需要明确说明您使用的是C库。您可以通过使用FFPEG包含ExtN”C来实现这一点。“

您是否尝试链接AVUTIL和AVFALTY？谢谢您的输入！错误依然存在。调用：GCC C++链接器G++/LoWork/WorkStudio /VIELIOB/-O“VIEWFECONDECONDENT”./LavoCDEC - Lavutle-LavFrase:LpTyth./VIEWFECCODCOR.O:函数<代码> VIEOTHONECODEL示例：/home /安德斯/WorkStudio /Debug…/VIEWFECCODCOR.CC：208：未定义的引用< /COD> AVCODECYFADY编码器（CODECID）“/home/anders/workspace/videofeccode/Debug/。/videofeccoder.cc:214:avcodec\u alloc\u context3（avcodec*）”的未定义引用/home/anders/workspace/videofeccode/Debug（..）您能在这里发布整个程序吗？我将尝试自己链接它并查看（使用相同的操作系统）。我用libav做了很多项目，但那是很久以前的事了，我再也没有makefile了。我记得这有点棘手，但最终还是奏效了。您是否尝试设置-L以确保它是正确的libavcodec？根据我发现的一些示例，您只需要“-lavformat-lavcodec-lz”您是否尝试过g++videofeccoder.cc-lavformat-lavcodec-lavutil？您提供库以链接到matters的顺序。@DvirVolk，以下是与libavcodec相关的代码：我想我尝试使用了“-L”选项。我正在尝试以并行方式链接另一个项目中的OpenFEC库，并且在其中一个/两个项目中都使用了'-L'。。我现在正在VirtualBox上安装32位Ubuntu，看看它是否能更好地链接这些库。。我还没有设法链接这个库和OpenFEC（在这两种情况下都是“未定义的引用”）。谢谢你的帮助！FFmpeg应该在头文件中真正考虑到这一点。C++是一种现实。

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