g++ errors, main.cpp last

jason@jason-System-Product-Name:~/workspace/ffmpeg_practice_2$ g++ -g -D__STDC_CONSTANT_MACROS -L/usr/local/lib/ -lswscale -lavformat -lavcodec main.cpp
main.cpp: In function ‘int main()’:
main.cpp:255:12: warning: ‘AVFrame* avcodec_alloc_frame()’ is deprecated (declared at /usr/local/include/libavcodec/avcodec.h:3422) [-Wdeprecated-declarations]
main.cpp:255:32: warning: ‘AVFrame* avcodec_alloc_frame()’ is deprecated (declared at /usr/local/include/libavcodec/avcodec.h:3422) [-Wdeprecated-declarations]
main.cpp:256:15: warning: ‘AVFrame* avcodec_alloc_frame()’ is deprecated (declared at /usr/local/include/libavcodec/avcodec.h:3422) [-Wdeprecated-declarations]
main.cpp:256:35: warning: ‘AVFrame* avcodec_alloc_frame()’ is deprecated (declared at /usr/local/include/libavcodec/avcodec.h:3422) [-Wdeprecated-declarations]
/tmp/cc1s47i8.o: In function `fetch_and_decode(int, AVCodecContext*, AVFrame*, AVCodec*)':
/home/jason/workspace/ffmpeg_practice_2/main.cpp:164: undefined reference to `av_init_packet'
/home/jason/workspace/ffmpeg_practice_2/main.cpp:171: undefined reference to `avcodec_decode_video2'
/tmp/cc1s47i8.o: In function `main':
/home/jason/workspace/ffmpeg_practice_2/main.cpp:235: undefined reference to `avcodec_register_all'
/home/jason/workspace/ffmpeg_practice_2/main.cpp:236: undefined reference to `av_register_all'
/home/jason/workspace/ffmpeg_practice_2/main.cpp:238: undefined reference to `avcodec_find_decoder'
/home/jason/workspace/ffmpeg_practice_2/main.cpp:241: undefined reference to `avcodec_alloc_context3'
/home/jason/workspace/ffmpeg_practice_2/main.cpp:242: undefined reference to `avcodec_open2'
/home/jason/workspace/ffmpeg_practice_2/main.cpp:255: undefined reference to `avcodec_alloc_frame'
/home/jason/workspace/ffmpeg_practice_2/main.cpp:256: undefined reference to `avcodec_alloc_frame'
/home/jason/workspace/ffmpeg_practice_2/main.cpp:259: undefined reference to `avpicture_get_size'
/home/jason/workspace/ffmpeg_practice_2/main.cpp:259: undefined reference to `av_mallocz'
/home/jason/workspace/ffmpeg_practice_2/main.cpp:263: undefined reference to `avpicture_fill'
/home/jason/workspace/ffmpeg_practice_2/main.cpp:268: undefined reference to `sws_getContext'
/home/jason/workspace/ffmpeg_practice_2/main.cpp:274: undefined reference to `avcodec_close'
/home/jason/workspace/ffmpeg_practice_2/main.cpp:275: undefined reference to `av_free'
/home/jason/workspace/ffmpeg_practice_2/main.cpp:276: undefined reference to `av_free'
/home/jason/workspace/ffmpeg_practice_2/main.cpp:277: undefined reference to `av_free'
collect2: ld returned 1 exit status