System version is Squeeze. Integred sound card's capture function not working.
 

~$ head -n 1 /proc/asound/card0/codec*
==> /proc/asound/card0/codec#0 <==
Codec: Realtek ALC269

==> /proc/asound/card0/codec#3 <==
Codec: Intel G45 DEVCTG


Volume control-> recording tab, phones of capture and digital both got a red fork. The fork appears again if volume control being opened even if you have removed the fork before closing it.

Anybody knows how to solve this problem?

Thanks a lot.

Open alsamixer, press F4 to swith to the capture devices and check if it says L---R and not dashes (-----) under the device you wish to capture from.

Yes. There are dashes under capture. Is that means hardware not working? Thanks.Attachment 10676

It means it is muted. Go there and press spacebar or enter or m (i don't remember which one is it) to unmute it and raise its levels.

Attachment 10686

Dashes gone when press spacebar. But phone icons of capture and digital still have the red fork and cannot be removed. As showed in the image above.