Niezdefiniowane odniesienie, przy użyciu biblioteki FFMpeg (AvCodec) w systemie Ubuntu, system 64-bitowy

Question

Uruchomiłem przykładowy kod najnowszej biblioteki FFMpeg. Wprowadziłem przykładowy kod w pliku 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 <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; 
} 

Kiedy biegnę gcc videofecencoder.cc -lavcodec otrzymuję wiadomości następujący błąd:

/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 

Komenda nm libavcodec.a | grep avcodec_find wyniki w:

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 

Mam również inny podobny błąd w innej bibliotece: Undefined reference despite linking in OpenFEC-library

Mój system: Ubuntu 11, maszyna 64-bity

Moim następnym krokiem jest, aby spróbować skompilować go na VirtualBox Ubuntu 32 bity (bieganie na Windows-OS).

Answer 1

byłem (wreszcie !!) odniósł się do roztworu w liście FFMpeg-mailowych: http://ffmpeg.org/faq.html#I_0027m-using-FFmpeg-from-within-my-C_002b_002b-application-but-the-linker-complains-about-missing-symbols-which-seem-to-be-available_002e

Cytat: „FFmpeg jest czystym projekt C, tak aby korzystać z biblioteki w swoim C++ aplikacji trzeba jawnie oświadczyć, że używasz biblioteki C. Możesz to zrobić, obejmując swoją FFmpeg obejmuje użycie zewnętrznego "C". "