Re: [Openvortex-dev] Stereo swapping.

[J. Gordon Wolfe]

Ok, here goes.  Hope I don't leave anything important out.

Intel Pentium III 850MHz
Mainboard Intel SE440BX-2
RAM: 512MB SDRAM (mix of PC100 and PC133 all running at 100MHz)
Aureal Vortex 2: Aureal SQ2500 rev fa on its own IRQ
Video: NVidia GeForce2 MX with NVidia driver rev 3123 (just in case it
matters, because I've heard rumours of nvidia's drivers doing strange
things before)
In fact, while I'm at it, maybe this whole thing is some weird hardware
conflict, so:
NIC: 3Com 905C-TX-M with 3Com's 3c90x linux driver
SCSI: Adaptec AHA-3940UW (78xx driver)

Distro: Gentoo, vanilla kernel 2.4.21, mostly stable packages
Environment: Gnome 2.2, no worthless sound daemons, alsa source patched
with Ryan's kickass ac97 patch for enabling 4-speaker output

Listen to MP3's, OGG's, and FLAC's through XMMS with the alsa plugin
0.9.9b.  Watch movies with mplayer and dvds with ogle.  I've got gaim
using aplay to play monaural wav files for events.  With the alsa
drivers I've only played NWN (linux client), though seeing your post has
made me think maybe I want to find my UT CD and try that.  I haven't
tried to reproduce those clicks you're talking about since I'm lazy and
I don't have any low bitrate files hanging around that I know of.

Similar to someone else's post, stereo swapping seems to be a problem
that increases with time for me.  At least, I notice it more the longer
my playlist goes, and it gets absolutely nuts after playing NWN for a
few hours or when trying to watch a DVD.  It used to happen every now
and again with the aureal binary driver from sourceforge, but its much
more frequent with the alsa driver.  It also seems to switch back
sometimes with the alsa driver, which I don't recall ever happening with
the binary (take that with a grain of salt, my memory's not great).  As
far as I can tell its pretty application agnostic.  I have yet to find
an app where I don't notice it, except of course the monaural wav files
thank goodness!



I've been fumbling around with the alsa source trying to isolate the
problem, and while chances are I don't know what I'm talking about it,
I'll throw my thoughts down here just in case they trigger something
with someone who actually knows what they're doing:

My first thought was that it must be a weird race condition or
something, so I started looking at the callback functions in
au88x0_pcm.c, since those are AFAIK the only pieces of the driver that
are called during playback.  By throwing in some printk() statements, I
deduced that if any of the callbacks are at fault, it has to be the
pointer callback.  This made sense to me, since its purpose seems to be
updating the buffer, so it happens all the time.  Poking around some
more, I found that the pointer callback seems to only be called from
vortex_interrupt() in au88x0_core.c, which is apparently the function
that responds to IRQs.  Testing my theory of race conditions, I
spinlocked the whole thing, even though it probably wasn't necessary. 
Obviously, it didn't stop the channel swapping.  I also tried messing
with the spinlocks on the pointer callback in various ways, with no
success.  Now, vortex_interrupt() also calls vortex_adbdma_bufshift(),
which looks like it does all the actual work, but I don't really
understand it at all, so I've been unable to pursue this further.  My
current theory is that something is wrong in there though.


Guess that covers everything.  I'm keeping my fingers crossed!

 - Gordon


On Thu, 2003-06-26 at 20:10, Manuel Jander wrote:
> Hello,
> 
> Please, could anyone affected be the stereo swapping problem make a
> detailed description of hardware and software ?
> I have the following setup and i did never get such of problems. The
> only problem that still remains presistent on my computer is regarding
> some clicks i meantioned before when reproducing 8 bit samples with low
> sample rates (5000 - 22050 Hz)
> 
> Info like this would be usefull
> 
> AMD Athlon Thunderbird 1.4GHz
> Mainboard ECS K7S5A
> RAM: 256 MiB DDR
> Aureal Vortex 2: "Diamond MX300" and "Digital Research Vortex 2 PCI"
> Aureal Vortex 1: "Turtle Beach Montego 3DXStream"
> 
> Distro: Debian Unstable (mostly updated)
> Enviroment: Gnome2, without esd (since alsa driver supports multiple
> streams, so no need for esd, arts or whatever shit).
> I listen MP3 using XMMS with ALSA output plugin (sometimes OSS), watch
> movies with XINE and AVIPLAY. 
> Sometimes i play Legacy DOOM, Quake3, UnrealTournament, Unreal (using
> WINE), Return to Napali (with WINE), Tux Racer or Defendguin.
> 
> With none of them stereo swapping does happen.
> 
> Best Regards
> 
> Manuel Jander.