I'm running Ubuntu 11.10 and I'm trying xvidcap to record a screencast with audio from the microphone, however it can't record any sound:

$ xvidcap --file appo.avi --cap_geometry 700x500-0+0 
Error accessing sound input from /dev/dsp
Sound disabled!

Sure enough /dev/dsp doesn't even exist:

$ sudo ls -lh /dev/dsp
ls: cannot access /dev/dsp: No such file or directory

I found a blog post about fixing xvidcap sound input, however if I try the suggestion I get:

$ sudo modprobe snd-pcm-oss
FATAL: Module snd_pcm_oss not found.

So the question is, how can I create /dev/dsp?

The problem behind the problem is: how can I record sound from the microphone with xvidcap? So workarounds are welcome too.

UPDATE: I've followed the suggestion of James, and something has improved.

The error accessing /dev/dsp is gone, however now I get:

[oss @ 0x8e0c120] Estimating duration from bitrate, this may be inaccurate
xtoffmpeg.c add_audio_stream(): Can't initialize fifo for audio recording

Now when I record xvidcap appears in the recording tab of pavucontrol and I can choose Audio stream from Internal Audio Analog Stereo or Monitor of Internal Audio Analog Stereo, I tried both just in case, but the video is still mute.

UPDATE 2: I found that "Monitor of" is the one to record application sounds, while for microphone, I should choose "Internal Audio Analog Stereo". To rule out other problems, such as with the microphone, I tried with gnome-sound-recorder and it works. Actually I jumped on my chair, since the volume was too high! :-)