Reply to posting by Erik Jakobsen, Audio problem, of 9/1/08.
It sounds like your problem is as follows, so please correct where this is
wrong:
1. Playing an MP3, or other sound file such as a WAV, which goes through the
ALSA PCM driver
2. Using a player such as "aplay"
3. Using a mixer control such as "alsamixer"
4. You suspect that your ALSA configuration is wrong (is a miss?).
Some of this you may know, but your email is too short to identify your
level of expertise.
Information that you need to provide.
1. The sound card, and/or the audio hardware chips
2. If the audio hardware is built-in to the motherboard, and what
motherboard that is
Include the motherboard south-bridge chip manufacturer and model (see
"lspci")
4. What the mixer chip is.
5. What ALSA driver is being used.
6. What ALSA mixer driver is being used.
7. The configuration parameters being supplied to "configure".
If your ALSA configuration is off then it would be surprising that anything
works, it usually just refuses to load the wrong driver and you would get no
sound. It is not impossible to
mess it up though so you need to supply the names of your audio hardware,
and your ALSA modules. It could be a new situation that the drivers do not
handle yet !!!
It is possible that the mixer labeling is off.
The alsamixer gets the labeling from the mixer driver (by some fashion that
I have yet to discover).
The usual reason for this is that your audio card has a different mixer chip
than ALSA thinks it does. It then uses the wrong labels and probably
display controls
that your mixer does not have, and misses controls that your mixer does
have.
I have a motherboard built-in mixer (with more controls than I know what to
do with).
As an example of how it should be in alsamixer.
It has a master volume that controls the volume for all output, after the
inputs are mixed.
It has separate volume controls for each input to the mixer, one for PCM
outputs, one for CDROM output, one for LINE input, one for MIC input, etc...
The separate input volume controls allow the user to balance the mixer
inputs,
while the master volume controls the output level without disturbing the
balance.
This does work in alsamixer and should work that way for your card too.
They may be a bunch of volume controls for stereo effects, and 3D effects,
that affect all output. Just ignore those, or turn the effects off for now
using MUTE (M-key).
Things to do:
1. Find out by some independent means exactly what mixer chip is on your
card and include that information in future email.
- The audio card docs are not likely to tell you anything
-. You can look on the card and try to read the integrated circuit names.
-. If this is built-in sound on a motherboard, then it will be very
difficult to find the sound chips. I looked with a magnifier before the
board was installed and am still not sure I found the audio chips because it
does not match what ALSA is displaying.
2. Run "lspci -v" and look for your audio identification in the output.
This may not give the mixer chip but will give good information about which
ones are likely.
3. Run "more /proc/modules" and get the names of all the ALSA drivers.
They are the ones that start with "snd".
4. Run "rexima", and any other mixer your have, and see if the mixer
controls are different.
5. Play a CD and find out which controls affect the volume.
They should include CD-volume, and master-volume.
6. Play from another input source, such as Line or Mic, and see which volume
controls affect it. Find all the volume controls that affect it.
7. Determine if there is anything that master volume does affect. It could
be that your PCM output does not go through the master volume control (in
which case it is not a master volume
control). It could be that it is mislabeled and is some other control.
8. Almost every audio player has a volume control interface. You might try
them
all to see if any of them work.
It is likely they all go to the same mixer driver, so they all should fail
the same identical way.
9. If you compile ALSA separately from the Linux kernel compile, then make a
script that runs configure with all the your configuration
parameters.
You can then reliably modify and run it to re-configure ALSA, and can copy
that script in an email.
"./configure --with-x --enable-xxx --enable-yyy --etc --etc \
--etc --etc --etc \
--etc --etc --etc"
Put a space at the front of every continuation line (just to be safe, mine
would fail until I did that).
10. If you compile ALSA with the Linux kernel, then it is more difficult to
supply your configuration parameters, and I do not know a good
way to pass that information on. Look through your Linux kernel config and
tediously copy by hand all info related to audio ???
Wesley Johnson, Linux user since 1994.
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