running the first Qt + ffmpeg profram: undefined reference av_register_all

Question

I am trying to include ffmpeg in my qt project on windows (I use QT Creator). I wrote a small program.

#include <iostream>

#ifdef __cplusplus
extern "C" {
#endif
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libswscale/swscale.h>
#ifdef __cplusplus
}
#endif

using namespace std;

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

    av_register_all();

    return 0;
}

And here is the problem

undefined reference av_register_all

Please help me to fix it.