[AG-TECH] Does OSS Free support full duplex?

James Miller millerjw at mailer.psc.edu
Tue Jun 18 14:24:31 CDT 2002

We had the exact same problem.  We solved it by switching the left and right
output channels from the soundcard to the inputs of the Matchmaker.  (L-out
from the sound blaster connects to R-in of the matchmaker and visa-versa.)
Sounds strange, but it removed the loopback issues.

Jim Miller

-----Original Message-----
From: Leslie Arvin [mailto:arvin at stat.purdue.edu] 
Sent: Tuesday, June 18, 2002 2:28 PM
To: richardc at cs.utah.edu
Cc: ag-tech at mcs.anl.gov
Subject: Re: [AG-TECH] Does OSS Free support full duplex?

richardc at cs.utah.edu wrote:
> Hi all,
> I've just loaded a machine with RedHat 7.2, and I'm getting feedback 
> problems. This is indicative of a problem with the hardware loopback 
> enabled on the PCI128 cards.
> I haven't loaded the commercial OpenSound drivers yet, because I was 
> hoping the free OSS drivers were more robust with this release of 
> RedHat.
> Is there a magic flag or setting I haven't touched? Or, do I need to 
> purchase the opensound drivers?
> -Richard

We encountered the problem with the SoundBlaster PCI 512 sound cards with
the RedHat 6.2 AGiB setup where the line-out from the card was being
looped-back to line-in.

Both the oss driver and emu10k1 driver exhibited this problem. The following
commands will turn off this loopback with the emu10k1

  /usr/local/bin/emu-dspmgr -r"Analog L:Rear L"
  /usr/local/bin/emu-dspmgr -r"Analog R:Rear R"

If anyone knows how to turn this off with the oss driver, I'd appreciate the
solution.  We're currently doing fine with the emu10k1 driver, but it's nice
to have options.

Is this case similar to your problem?

-- Leslie Arvin
   arvin at stat.purdue.edu
   Purdue University

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