Comment 14 for bug 290728

I am trying to record the screen with xvidcap in ubuntu 9.04 version...video is recorded in very good quality but there is no audio....after I stop recording there comes a box saying Audio Codec : None....and I tried to change the audio codec but there is no option for audio in preferences ...I am new with linux so I dont know much,,,,reading upper comments I tried this command in terminal but it didn work..
$ sudo apt-get install libavcodec-unstripped-51
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Couldn't find package libavcodec-unstripped-51

Please help me fix the audio.

Thanks in advance.