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Date: Sat, 21 Jun 1997 02:18:37 -0700
From: John-Mark Gurney <jmg@hydrogen.nike.efn.org>
To: Mark Murray <mark@grondar.za>
Cc: multimedia@FreeBSD.ORG
Subject: Re: GUS PnP woes
References: <199706210833.KAA08887@greenpeace.grondar.za>
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Organization: Cu Networking
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Mark Murray scribbled this message on Jun 21:
> Amancio Hasty wrote:
> > That looks more like a bug with speak_freely than with the
> > sound driver. Please make sure that speak_freely does indeed
> > attempt to open /dev/audio or /dev/dsp with RW .
> > 
> > If it tries to open /dev/audio0 for playback and /dev/audio1 for reading
> > the sound driver will fail. This mode of full duplex audio was used
> > in pre Sound Driver 3.5 drivers.
> 
> Hmmm...
> 
> Two processes can't open /dev/audio. How should this work?

see below, they can if one is a child of another...

> Speak_freely has one process doing the reading and one doing the 
> writing. The one that starts second cannot get /dev/audio because it is 
> busy. This can be duplicated by going 'cat /dev/audio > /dev/audio'.

so you simply do something like:

int fd;
fd=open("/dev/audio", O_RDWR);
if(fork()) {
	handle one end;
} else {
	handle the other;
}

really quite simple...  and the seperate audio{0,1} was probably so you
could simulate full duplex audio with two sound cards... one as audio0
and the other as audio1...

-- 
  John-Mark Gurney                          Modem/FAX: +1 541 683 6954
  Cu Networking

  Live in Peace, destroy Micro$oft, support free software, run FreeBSD