Re: This OUGHT to be easy, but I'm a bit lost...

[Takashi Iwai <tiwai@suse.de>]

At Tue, 3 Jun 2003 01:46:06 -0700 (PDT),
Tom Watson wrote:
> 
> I'm just attempting to write a simple playback routine.  Yes, I know
> that 'aplay' exists, but I need some more goodies, and 'aplay' is too
> complex in other areas.
> 
> I've got a multi-channel interleaved sound file (1-6 channels for the
> sake of argument) and I'd like it to reproduce.  In AC-97 sound
> hardware (the motherboard has a VIA 82XX chip set) I need to setup the
> rear outputs to come out the "line-in" jack, and the 5th and 6th
> channels come out the Mic jack.

this is rather the problem of mixer configuration.
in general, however, you can play via "surround51" pcm:

	% aplay -Dsurround51 six-chs.wav

don't forget to raise and unmute "surround" and "center/lfe" volumes.

> I'd like to have 2 channel sound
> OPTIONALLY "double up" and at option come out the "rear" outputs.  I
> wrote programs to do this under OSS (granted it WAS an CMI chip set,
> but the same jacks existed, and the same controls had to be set).  I
> would like to set these controls with the amixer command line program
> (the final program will have NO GUI's at ALL).
 
some codecs have already a mixer switch to do that on hardware
(e.g. ALC650).  or, some driver (e.g. ymfpci) supports it.  in theory,
it's not difficult on emu10k1, too.

if you do that on software, you can do it by adding a new pcm to
~/.asoundrc with copy plugin.


> In addition, I have a Turtle Beach Santa Cruz card (CS42xx chip set). 
> It has nice things like front and rear outputs (even leveled on the
> card!!).  I have my CD player wired into this, and need the mixer
> controls to make this work as well.  The difficult part is finding out
> exactly the command line to make it work.  It is a bit confusing.

routing the analog CD input to the arbitrary analog/digital out is
difficult in general.  only some chip does support it.  i forgot
whether cs46xx can do that.

instead of hardware wiring, you can do it all in digital, i.e. reading
via CDDA and sending the PCM data, so that you can handle everything
as you like.


Takashi


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