I had problem with alsa (alsamixer) on my CentOS. The problem was like this.
/etc/asound.conf had a hooks section.
The hooks section introduced another sound card and I was not able to use the microphone after that.
After deleting the
@hooks section the problem was gone.
The very useful facts about alsa are:
/proc/asound/ – this folder actually determines if alsa is present on the system or not.
alsactl restore 0 – sound card 0 info will be restored
alsactl store – this enables alsa to store permanent values
arecord -vv -d 10 test.wav – creates a file after 10 seconds of recording with the visual equalizer
aplay -vv test.wav – plays the file
alsamixer – of course the most important to set the levels
pulseaudio --kill – eliminates pulse audio
pulseaudio --start – starts pulse audio
pacmd list – closer look to pulse audio
The best info about Alsa I found here http://www.seehuhn.de/pages/alsa and here: https://wiki.archlinux.org/index.php/PulseAudio
ALSA is the kernel level sound mixer, it manages your sound card directly.
ALSA by itself can only handle one application at a time. This may be a problem, but there is dmix module, written to solve the problem of one application at a time.
PulseAudio is a software mixer, on top of the userland (like you’d run an app). When it runs, it uses Alsa’s channel – without dmix – and manages every kind of mixing, the devices, network devices, everything by itself.