[kde-freebsd] KSayit questions... .

[Gary Kline]

On Wed, May 23, 2007 at 04:29:02PM +0100, Bartosz Fabianowski wrote:
> >I still don't understand how arts, oss, and esd work together.
> 
> It's pretty simple really. Traditionally, OSS encapsulates the sound 
> driver and provides access to the sound card through the /dev/dsp 
> device. Unfortunately, this device can be opened for writing only by a 
> single process at a time. As multimedia became more prevalent, people 
> wanted to be able to play multiple sounds at once, say to listen to an 
> MP3 but also get system notifications via jingles. The way this was 
> solved was through a sound server - a daemon that opens /dev/dsp and 
> then multiplexes whatever audio other processes send to it. KDE adopted 
> the aRts daemon, GNOME chose ESD. So, now, you have two competing 
> daemons, each of which is able to multiplex sound sources but also needs 
> exclusive access to /dev/dsp to do its work. Needless to say, this is 
> bound to fail - only artsd or esd can open the device at any given time. 
> To solve this dilemma, you enable vchans - a multiplexing facility in 
> the FreeBSD kernel that presents several "virtual" sound cards as 
> numbered /dev/dspX devices. artsd can then connect to one of those, esd 
> to another and FreeBSD takes care of multiplexing their outputs into one 
> stream that is fed to the actual sound card.
> 

	Wow; this is a concisr and *clear* tutorial, thanks very much
	indeed.  I'm guessing that this audio multiplexor is a new
	feature.  (I never did do much kernel hacking, but whenever I did
	grep into the snd code years back, I don't remember seeing it.)

	Somehow, (zero ideas), things-audio worked out of the box when I
	began building my DNS replacemnt.  The box [a KAYAK] is very old
	and very beefy; i'll use it when/if my present DNS server dies.
	One thing that has bothered me on present FBSD and Ubuntu servers
	is the notice that "/dev/dsp is in use" ...  and greps thru 
	ps ax and even rebooting often failure to let me play streams or
	whatever.  Without looking thru the kernel code, does this
	sound familiar?  --I thought I'd ask before adding multiple
	vhans:-)

	danke! [bar]

	gary


> HTH
> - Bartosz

-- 
  Gary Kline  kline at thought.org   www.thought.org  Public Service Unix