Re: sblive 4ch output w/ jack - asoundrc magic?

[Takashi Iwai <tiwai@suse.de>]

At Thu, 05 Feb 2004 20:26:10 +0100,
Joern Nettingsmeier wrote:
> 
> Takashi Iwai wrote:
> > At Thu, 05 Feb 2004 00:08:18 +0100,
> > Joern Nettingsmeier wrote:
> > 
> >>[crossposted to alsa-devel and jackit-devel]
> 
> [removed jackit-devel from cc:]
> 
> >>
> >>hi *!
> >>
> >>i'd like to use the rear outs of my sblive platinum with jack.
> >>
> >>the following works:
> >># aplay some.wav -Dfront &
> >># aplay someother.wav -Drear
> >>both signals end up at my mixer as expected, so it seems the devices 
> >>are independent.
> >>
> >>front is hw:0,0 which is a duplex device.
> >>rear is hw:0,3 and is playback only.
> > 
> >  
> > hmm?  hw:0,3 isn't for the rear output...
> 
> not?
> 
> then what is it?

it's FX8010 PCM output, mainly used for the spdif output.


> and is hw:0,0 a four-channel out, two channel in device?

hw:0,0 is used for all analog outputs.
basically it supports mono or 2-channel sterem streams, up to 32
streams simultaneously.
it has a hardware routing table per voice.  by tuning this table, you
can send the output to front, rear or center/lfe FX bus.
you can find the trick in /usr/share/alsa/cards/EMU10k1.conf file.


> i've had this card for a couple of years now, and i still don't 
> understand a fraction of it...
> 
> is the relationship of in and out jacks, mixer strips and alsa 
> devices documented somewhere?

alsa-kernel/Documentation/SB-Live-mixer.txt.

the only sure way to access the certain channel is to use the
pre-defined pcm name, such as "front", "surround40", "rear" and
"iec958".  it assures that the output comes from the front jack
regardless of soundcard, and regardless what magic is done.

accessing via "hw" pcm is no sure way.  it allows you to access
*directly* to the hardware, but then you have to tune up by yourself.


Takashi


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