[PATCH] pmac: sound support for latest laptops

[Benjamin Herrenschmidt]

On Mon, 2005-04-11 at 17:07 +0200, Johannes Berg wrote:
> Hi,
> 
> >This patch hacks the current Alsa snd-powermac driver to add support for
> >recent machine models with the tas3004 chip, that is basically new
> >laptop models. The Mac Mini is _NOT_ yet supported by this patch (soon
> >soon ...). The G5s (iMac or Desktop) will need the rewritten sound
> >driver on which I'm working on (I _might_ get a hack for analog only on
> >some G5s on the current driver, but no promise).
> >  
> >
> That's cool. I do have one slight problem with it though: When I turn 
> down the Master mixer and up PCM it sounds badly overmodulated. I can 
> keep PCM at about 75% and turn up master, and all is fine. Would it make 
> sense to limit the PCM mixer to about 75% of its current limits, or how 
> does that actually work in the hardware?

Well, the driver will let you do the setting you want, even if it's
wrong :) You should indeed keep PCM at about 75% and use the master.

There is also an issue with bad quality speakers used by Apple. OS X has
a built-in software DSP that does equalisation & filtering in the kernel
driver, and they have specific settings for it for various machine model
speakers. Obviously, we don't have such thing.

Ben.