No Sound ?

[Guest anon]

SOUND

There are many variables which affect why sound will or will not work. They dall into the following major categories:

1. ISA sound card unrecognized.

2. ALSA loaded for a sound card that works only with OSS.

3. Inappropriate use of harddrake and sndconfig which overloads sound with two or more drivers.

4. Use of gdm as a login manager which has a tendency to forget to transfer ownership of the sound devices to the logged-in user.

5. A change of user number which causes the same effect, non-ownership of sound device files until the files that control this are initialized with the new user number.

ISA

It is usually easy to detect an ISA soundcard if you are a user. If the card fits in the black slots rather than the white or brown ones on your motherboard, then it is ISA. There are specifics for this configuration which are documented if you happen to have one. It will not be detailed here. Please note that new motherboards have one or no ISA slots now and they call the ISA slot "Legacy". No cases of on-board sound have been shown to use ISA.

PCI

Sound cards and on-board audio are usually this interface today. The question becomes,

ALSA, OSS, or proprietary?

ALSA is default set up unless no ALSA drivers exist. ALSA (Advanced Linux Sound Architecture) is an effort to take a kernel not really designed for sound editing and to add a huge repository of options. Multiple sound cards are possible and many cards run in an OSS-compatibility mode.

OSS (Open Sound Systems) is a combination of proprietary support from www.opensound.com and drivers they have released openly after paying the cost of development.

Some sound cards now come with linux drivers. Generally speaking, there should be at least a source wrapper for the sound driver so that it can be compiled as a kernel module. Some sound drivers are provided along with video drivers for special boards, such as those based on the NForce chipset.

WHAT TO DO IF SOUND DOESN'T WORK.

We are not covering digital Dolby sound or USB headphone issues here, but what happens if the KDE start theme doesn't play when KDE comes up for the first time? GNOME won't play sound events until the user logs in to Sawfish and selects Configuration=>sound from the menu and check both boxes on the window that pops up, then logs out and logs into GNOME.

First

run

lspcidrake

does a sound facility show?

If so, you can proceed. If not, you probably have ISA sound.

Now run

cat /etc/modules.conf

likely this will show sound modules being loaded like this:

alias sound-slot-0 snd-card-i8x0_audio

above ... pcm-snd-oss

That is an actual non-working setup for the SiS 735 chipset which sndconfig will tell you is the SiS 7012 sound card which is unsupported.

To make it work, we edit /etc/modules.conf

alias sound i810_audio

replaces the two former lines and then everything works.

And for the SiS 630,

alias sound trident

will work just fine while the setup from install will rarely work.

The SiS 620 and 530 may require the Yamaha YMF or the ESSSolo1 drivers, again in an OSS configuration (single sound card).

So what happens if the ALSA driver is loaded and someone uses sndconfig to load the OSS driver?

Variable results occur. Sound may die after 10 minutes, or sound very scratchy, or just not work at all or work very well indeed. If you have sound and

chkconfig --del alsa

leaves you with sound still running, it is likely you had both drivers loaded.

SCENARIOS

#1 NO SOUND and KDE souns server gives error message, but lspcidrake shows a sound facility and /etc/modules.conf has one or more sound aliases, AND volume controls are set high enough to hear sound if it is playing.

Use lspcidrake and the modules information to hunt down a driver for the sound at

file:/lib/modules/2.4.18-6mdk/kernel/drivers/sound

Try taking out the sound configuration shown in /etc/modules.conf and substituting

alias sound (modulename)

stripping the .o.gz from the name of the file you want to try.

It is best to first try (in a superuser terminal window)

# chkconfig --del alsa

# modprobe (modulename)

If you get error messages, then your driver choice is incorrect and you move on to the next on your list of candidates, until you find one that installs or run out of modules.

Once tha alias is found, save /etc/modules.conf and reboot. You should now hear something.

SCENARIO

#2 I HAVE SOUND BUT THE CD DOESN'T PLAY AUDIO...

There are several reasons why this may happen:

a. You have a cheapie computer built windows ME time or later which omitted the 3-wire audio cable between the CD drive and the sound card. (This fix costs $2.00) NOT CHECKING for it may cost days.

b. You have a CDRW and /dev/cdrom doesn't point to /dev/scd0

Superuser terminal window

# ln -fs /dev/scd0 /dev/cdrom

Note that since sound plays off of /dev/cdrom by default, if you have TWO CD type devices (as in a DVD and a CDRW) ONE of them will play and the other will not.

Often the DVD will provide sound for movies even though it will not play audio CDs because movie sound is usually drawn from /dev/dvd.

c. You have a DVD drive and it doesn't play audio and it is your only CD type device, let's say for example it is /dev/hdc (you can check the output of dmesg to discover which one it is).

Terminal window as superuser

# ln -fs /dev/hdc /dev/cdrom

# ln -fs /dev/hdc /dev/dvd

Yes unfortunately, many install scenarios leave the /dev/dvd link hanging without a referent.