Date: Tue, 29 Mar 2005 12:02:12 +0200
Message-ID: <s5h8y46kbx7.wl@alsa2.suse.de>
From: Takashi Iwai <tiwai@suse.de>
To: Lee Revell <rlrevell@joe-job.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
       Linux Kernel list <linux-kernel@vger.kernel.org>
Subject: Re: Mac mini sound woes
In-Reply-To: <1112067369.19014.24.camel@mindpipe>
References: <1111966920.5409.27.camel@gaston>
	<1112067369.19014.24.camel@mindpipe>
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At Mon, 28 Mar 2005 22:36:09 -0500,
Lee Revell wrote:
> 
> On Mon, 2005-03-28 at 09:42 +1000, Benjamin Herrenschmidt wrote:
> > It seems that Apple's driver has an in-kernel framework for doing volume
> > control, mixing, and other horrors right in the kernel, in temporary
> > buffers, just before they get DMA'ed (gack !)
> > 
> > I want to avoid something like that. How "friendly" would Alsa be to
> > drivers that don't have any HW volume control capability ? Does typical
> > userland libraries provide software processing volume control ? Do you
> > suggest I just don't do any control ? Or should I implement a double
> > buffer scheme with software gain as well in the kernel driver ?
> 
> alsa-lib handles both mixing (dmix plugin) and volume control (softvol
> plugin) in software for codecs like this that don't do it in hardware.
> Since Windows does mixing and volume control in the kernel (ugh) it's
> increasingly common to find devices that cannot do these.  You don't
> need to handle it in the driver at all.

Yes.

> dmix has been around for a while but softvol plugin is very new, you
> will need ALSA CVS or the upcoming 1.0.9 release.

dmix currently doesn't work on PPC well but I'll fix it soon later.
If it's confirmed to work, we can set dmix/softvol plugins for default
of snd-powermac driver configuration.  Hopefully this will be finished
before 1.0.9 final.


Takashi
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