streaming AAC (mpeg4 audio)

[firehat]

Hi,
i use vlc for streaming dvb channel ,the os is ubuntu 8.10.
when i use mpeg audio or a52 the streaming channel is a good audio,but if i use AAC(mpeg 4audio), the channel has no audio .

help me

[firehat]

there is the error: ffmpeg encoder error cannot find encoder mpeg aac audio
how to correct ?