Ffmpeg + sdl + qt

This error occurs when you are working on the ffmpeg + Qt + SDL project,
/Usr/local/lib/libavdevice. a (alsa-audio-dec.o): In function 'audio _ read_packet ':
/Opt/libav-0.6.2/libavdevice/alsa-audio-dec.c: 139: undefined reference to 'snd _ pcm_readi'
/Opt/libav-0.6.2/libavdevice/alsa-audio-dec.c: 146: undefined reference to 'snd _ strerror'
/Opt/libav-0.6.2/libavdevice/alsa-audio-dec.c: 154: undefined reference to 'snd _ pcm_htimestamp'
/Usr/local/lib/libavdevice. a (alsa-audio-dec.o): In function 'audio _ read_header ':
/Opt/libav-0.6.2/libavdevice/alsa-audio-dec.c: 90: undefined reference to 'snd _ pcm_type'
/Opt/libav-0.6.2/libavdevice/alsa-audio-dec.c: 95: undefined reference to 'snd _ pcm_sw_params_malloc'
/Opt/libav-0.6.2/libavdevice/alsa-audio-dec.c: 97: undefined reference to 'snd _ strerror'
/Opt/libav-0.6.2/libavdevice/alsa-audio-dec.c: 102: undefined reference to 'snd _ pcm_sw_params_current'
/Opt/libav-0.6.2/libavdevice/alsa-audio-dec.c: 103: undefined reference to 'snd _ pcm_sw_params_set_tstamp_mode'
/Opt/libav-0.6.2/libavdevice/alsa-audio-dec.c: 105: undefined reference to 'snd _ pcm_sw_params'
/Opt/libav-0.6.2/libavdevice/alsa-audio-dec.c: 106: undefined reference to 'snd _ pcm_sw_params_free'
/Opt/libav-0.6.2/libavdevice/alsa-audio-dec.c: 108: undefined reference to 'snd _ strerror'
/Opt/libav-0.6.2/libavdevice/alsa-audio-dec.c: 123: undefined reference to 'snd _ pcm_close'
/Usr/local/lib/libavdevice. a (alsa-audio-enc.o): In function 'audio_write_packet ':
/Opt/libav-0.6.2/libavdevice/alsa-audio-enc.c: 79: undefined reference to 'snd _ pcm_writei'
/Opt/libav-0.6.2/libavdevice/alsa-audio-enc.c: 86: undefined reference to 'snd _ strerror'
/Usr/local/lib/libavdevice. a (alsa-audio-enc.o): In function 'audio _ write_header ':
/Opt/libav-0.6.2/libavdevice/alsa-audio-enc.c: 68: undefined reference to 'snd _ pcm_close'
/Usr/local/lib/libavdevice. a (alsa-audio-common.o): In function 'ff _ alsa_xrun_recover ':
/Opt/libav-0.6.2/libavdevice/alsa-audio-common.c: 174: undefined reference to 'snd _ pcm_prepare'
/Opt/libav-0.6.2/libavdevice/alsa-audio-common.c: 176: undefined reference to 'snd _ strerror'
/Usr/local/lib/libavdevice. a (alsa-audio-common.o): In function 'ff _ alsa_open ':
/Opt/libav-0.6.2/libavdevice/alsa-audio-common.c: 73: undefined reference to 'snd _ pcm_open'
/Opt/libav-0.6.2/libavdevice/alsa-audio-common.c: 75: undefined reference to 'snd _ strerror'
/Opt/libav-0.6.2/libavdevice/alsa-audio-common.c: 80: undefined reference to 'snd _ pcm_hw_params_malloc'
/Opt/libav-0.6.2/libavdevice/alsa-audio-common.c: 82: undefined reference to 'snd _ strerror'
/Opt/libav-0.6.2/libavdevice/alsa-audio-common.c: 87: undefined reference to 'snd _ pcm_hw_params_any'
/Opt/libav-0.6.2/libavdevice/alsa-audio-common.c: 89: undefined reference to 'snd _ strerror'
/Opt/libav-0.6.2/libavdevice/alsa-audio-common.c: 94: undefined reference to 'snd _ pcm_hw_params_set_access'
/Opt/libav-0.6.2/libavdevice/alsa-audio-common.c: 96: undefined reference to 'snd _ strerror'
/Opt/libav-0.6.2/libavdevice/alsa-audio-common.c: 101: undefined reference to 'snd _ pcm_hw_params_set_format'
/Opt/libav-0.6.2/libavdevice/alsa-audio-common.c: 103: undefined reference to 'snd _ strerror'
/Opt/libav-0.6.2/libavdevice/alsa-audio-common.c: 108: undefined reference to 'snd _ pcm_hw_params_set_rate_near'
/Opt/libav-0.6.2/libavdevice/alsa-audio-common.c: 110: undefined reference to 'snd _ strerror'
/Opt/libav-0.6.2/libavdevice/alsa-audio-common.c: 115: undefined reference to 'snd _ pcm_hw_params_set_channels'
/Opt/libav-0.6.2/libavdevice/alsa-audio-common.c: 117: undefined reference to 'snd _ strerror'
/Opt/libav-0.6.2/libavdevice/alsa-audio-common.c: 122: undefined reference to 'snd _ pcm_hw_params_get_buffer_size_max'
/Opt/libav-0.6.2/libavdevice/alsa-audio-common.c: 124: undefined reference to 'snd _ pcm_hw_params_set_buffer_size_near'
/Opt/libav-0.6.2/libavdevice/alsa-audio-common.c: 126: undefined reference to 'snd _ strerror'
/Opt/libav-0.6.2/libavdevice/alsa-audio-common.c: 131: undefined reference to 'snd _ pcm_hw_params_get_period_size_min'
/Opt/libav-0.6.2/libavdevice/alsa-audio-common.c: 132: undefined reference to 'snd _ pcm_hw_params_set_period_size_near'
/Opt/libav-0.6.2/libavdevice/alsa-audio-common.c: 134: undefined reference to 'snd _ strerror'
/Opt/libav-0.6.2/libavdevice/alsa-audio-common.c: 140: undefined reference to 'snd _ pcm_hw_params'
/Opt/libav-0.6.2/libavdevice/alsa-audio-common.c: 142: undefined reference to 'snd _ strerror'
/Opt/libav-0.6.2/libavdevice/alsa-audio-common.c: 147: undefined reference to 'snd _ pcm_hw_params_free'
Make: Leaving directory '/home/jacky/workspace/Roarsoft/EasyPlayer-build-desktop'
/Opt/libav-0.6.2/libavdevice/alsa-audio-common.c: 153: undefined reference to 'snd _ pcm_hw_params_free'
/Opt/libav-0.6.2/libavdevice/alsa-audio-common.c: 155: undefined reference to 'snd _ pcm_close'
/Usr/local/lib/libavdevice. a (alsa-audio-common.o): In function 'ff _ alsa_close ':
/Opt/libav-0.6.2/libavdevice/alsa-audio-common.c: 163: undefined reference to 'snd _ pcm_close'