Distorted sound on -CURRENT

Hi all,

For a long time I have had problems with sound on my ThinkPad, which has
a rather sucky Crystal chipset. The problems consist of skips and pops
and crackles when playing back audio, and makes it hopeless to listen to
any kind of music while working (or playing ;).

There have been attempts at fixing this earlier, which has helped
somewhat, but I always thought this was a problem on my chipset only -
but this does not seem to be the case.

I have now tested in a machine that has a SB Live! card (snd_emu10k1
module), and I'm experience the same problems, just even more pronounced
than with the Crystal chipset.

The interesting thing is - this is a non-issue in all 4.x versions of
FreeBSD, and it's a non-issue in all other OSes I have tried on the
respective computers. I am therefore led to believe there has been some
kind of screwup with the PCM or chipset drivers in -CURRENT, or perhaps
in some underlying code. This has been a problem atleast since
5.1-RELEASE, and I do believe (but cannot confirm) it was a problem with
5.0-RELEASE aswell. Choice of scheduler (SCHED_4BSD or SCHED_ULE) has no
influence, neither has there been any difference before or after the
i386 interrupt code switch.

I home someone can have a look at this, it is of minor importance but
major annoyance - and personally I think it should be (attempted) fixed
before 5.2-RELEASE, if possible. It does make a bad impression on
people, even in a FreeBSD-house such as the one I am working for right
now.

Best regards,
Eirik Oeverby