neil topking

Hi,everyone!
The issue is the alsamixer always gives a broken output(make a pop
here and there) when playing back.
I emerged alsa and oss both on my laptop.OSS recognize my sound card
as an AD1981B card,not correct but works fine.ALSA seems to be
familiar with my sound card--Intel82801-ICH4.However,its output not so
exciting In windows,the card is recognized as SOUNDMAX.
This issue is trivial because I could use esd and oss instead.What I
want to know is:Is this a common issue?If so,any solution exists?
Thanks!

Jin Zhang

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bob sanders

The popping is not exactly normal. However, it could be related to cpu
loading, swapping, or a bad capacitor on the motherboard.

Skip the below paragrah if you know all about AC'97...
What is happening is this - Microsoft and Intel defined cheap hardwawre
spec's for sound back in the '90s. Commonly known as AC'97 Think of
it as WinAudio (and no they aren't the only ones that did this, some
Unix vendors perform this type of cheapness). So sound has to be generated
via the systems FPU, as there is no hardware DSP. Thus this software DSP
uses minimal hardware - usually in the Southbridge, to control, route, and
be master to a codec, in this case the AD1981B (marketing name - SoundMax).
The codec just provides the interface to the outside would in mainly an
analog fashion.

So popping is when the sound buffers are empty because data can't get to them
to keep them full. Audio data can be stalled in the FPU, the FPU is too busy,
memory is tied up, or the system is in some kind of massive context switch mode.

Popping can also occur if the electrolytic cap(s) assigned to the codec have
dried up or gone bad, allowing the voltage to the codec to sag in unision with
peaks of current draw - hard drive seeks, etc. Or some other hardware anomoly.

So, after all the above, useless crap, it works in WinXX, but not in Linux.
Some possibilites -

. the window manager is sucking life out of the system. Try a lightweight
window manager.
. the system is swapping it's brains out. Remove large processes or add
memory.
. something not quite right with the kernel. Remove or turn into modules,
un-needed kernel options. Make the kernel lighter weight. A good
resource is - http://dev.gentoo.org/~brix/papers/X31/X31.html

* Note - if you have a later model, don't go near CONFIG_ACPI_PROCESSOR
CONFIG_ACPI_FAN, and CONFIG_X86_PM_TIMER. The first two
will cause hangs or kernel panics during boot.

You might also want to peruse the archives at -

http://www.theshire.org/mailman/listinfo/linux31

FWIW - yes the onboard sound is lousy. I "fixed" mine by getting ($$$) a Headroom
Bithead (well, Total Bithead). Not only can I use it on my X31, but I can plug
in to any machine that supports ALSA USB audio or USB audio and listen to tunes.

Bob
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neil topking

Thanks,Bob
You really make things clear.The memory shouldn't be the
bottleneck.But the FPU may be.The pops happen more frequently when I'm
playing video by mplayer.And I note that mplayer complains there's no
mmx and sse support(I forgot USE).
I'll recompile mplayer with sse support to test this.

BTW,I've been considering to buy a USB-Audio stuff for a long time.But
I know nothing about it.Any suggestions?


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bob sanders

Hi Jin,

mmx will make a lot of difference - much more efficient. The x87 fpu
is pretty poor at doing DSP type of work.

There be tigers lurking in that direction...

Don't buy if you can't try. Some USB audio requires firmware to be loaded
before it functions. Some of the firmware is proprietary and some companies
don't allow it to be released, even in binary form, outside of their WinXX
drivers. And a lot of firmware is broken, in general.

You might want to browse the lad (linux-audio-developers) and the lau
(linux-audio-users) mailing list. There was a pretty sprited discussion
about USB audio devices and firmware loading on the lad list last
Oct or maybe it was Sep. See -

http://www.linuxdj.com/audio/lad/archive.php3

Also, surf to - http://www.linux-usb.org/ and take a look at what
others have working. Be aware that some of those are older listings.
Newer versions might have internal changes that function entirely
differently than what used to work.

But, here is the general deal with USB audio - for general use, on a
sufficently fast machine - >= 1GHz, it's fine. For more professional
use, the latencies are unacceptable. There is no way to insure that
the response will be under 3 ms.

For profesional audio, you'd want to look at ieee1394 (firewire). But,
again not all devices actually work well.

Bob
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neil topking

Thanks for your suggestions,Bob.I'll keep them in mind.

I recompiled mplayer with mmx,mmx2,sse&&sse2 support.It seems to be
much better,though the sounds are still lousy(this is its eigen
state).

Finally,thanks again.It's very nice of you to supply so much info.I
guess it'll take me a whole day to dig in

Jin Zhang


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holly bostick

No help or suggestions, just dropped in to celebrate the further spread
of Dutchlish (of Nederlengels)... I am glad to know I'm not the only
speaker of it, and that at least one other person (other than my
boyfriend) understands me when I speak it ;-)

(for unmixed English speakers-- "eigen"="typical").

Holly

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