[FFmpeg-user] Building Error avcodec_send_packet

[יוסף אלון]

I would like to compile to following program:
With the flages: -lavcodec -lavutil -lavfilter -lavformat -lswscale -lz

#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
#include "libswscale/swscale.h"

#include <stdio.h>

// The flush packet is a non-NULL packet with size 0 and data NULL
int decode(AVCodecContext *avctx, AVFrame *frame, int *got_frame, AVPacket
*pkt)
{
    int ret;

    *got_frame = 0;

    if (pkt) {
        ret = avcodec_send_packet(avctx, pkt);
        // In particular, we don't expect AVERROR(EAGAIN), because we read
all
        // decoded frames with avcodec_receive_frame() until done.
        if (ret < 0)
            return ret == AVERROR_EOF ? 0 : ret;
    }

    ret = avcodec_receive_frame(avctx, frame);
    if (ret < 0 && ret != AVERROR(EAGAIN) && ret != AVERROR_EOF)
        return ret;
    if (ret >= 0)
        *got_frame = 1;

    return 0;
}


int main(int argc, char *argv[]) {

  return 0;

But I receive:
undefined reference to `avcodec_send_packet'
undefined reference to `avcodec_receive_frame'

ffmpeg version is:
ffmpeg version 3.2.4 Copyright (c) 2000-2017 the FFmpeg developers
  built with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.4) 20160609
  configuration:
  libavutil      55. 34.101 / 55. 34.101
  libavcodec     57. 64.101 / 57. 64.101
  libavformat    57. 56.101 / 57. 56.101
  libavdevice    57.  1.100 / 57.  1.100
  libavfilter     6. 65.100 /  6. 65.100
  libswscale      4.  2.100 /  4.  2.100
  libswresample   2.  3.100 /  2.  3.100

Does some one know, Whats the problem?

-- Yosef Alon