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Re: [Qemu-devel] Soundwrapper and artsd (fails to share)

From: Jim C. Brown
Subject: Re: [Qemu-devel] Soundwrapper and artsd (fails to share)
Date: Sun, 5 Dec 2004 20:13:16 -0500
User-agent: Mutt/1.4i

On Mon, Dec 06, 2004 at 03:42:59AM +0300, malc wrote:
> On Mon, 6 Dec 2004, Richard Neill wrote:
> >Dear All,
> >
> >I wonder why the following doesn't seem to work? Qemu still takes an 
> >exclusive lock on the soundcard, even when invoked with soundwrapper.
> >I'm using this invocation:
> There is no such thing as excluse soundcard lock, /dev/dsp is being opened
> and if sound hardware does not support multiple hardware channels then 
> this is where the story ends.

Not at all. One can pipe the sound thru daemons such as Artsd, ESD, etc.
These daemons then muliplex the sound to the actual hardware. Of course
the programs have to be specially designed to use these daemons, but sometimes
you can use tricks to fool regular programs into thinking that they're talking
to the hardware when they are only sending messages to a pipe or socket. These
typically involve a wrapper of some sort.

Currently the wrappers don't work w/ qemu. (I've only tried 2, artsdsp and
esddsp). It isn't hard to add arts support to qemu, I just haven't had the time
to convert the code yet.

> >
> >soundwrapper /usr/local/bin/qemu -cdrom servicepacks.iso -hda 
> >winxp_pro_hd.img -boot c -localtime -enable-audio -m 256 -monitor stdio
> I'm not quite sure what soundwrapper is, but if it is just a script that
> calls artsdsp under the hood, then it's a no go:
> <quote>
> # artsdsp i386-softmmu/qemu
> artsdsp works only for binaries
> </quote>

I don't get this error. It doesn't even make sense, because A) artsdsp works
for scripts and B) qemu is a binary. artsdsp is merely a script that makes use
of the LD_PRELOAD trick, which wraps open(), write(), and a few other things
in order to intercept attempts to open /dev/dsp (and related audio devices)
and replace them with messages to artsd.

Of course, artsdsp doesn't work for qemu anyways, so it's a moot point.

Infinite complexity begets infinite beauty.
Infinite precision begets infinite perfection.

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