[gentoo-amd64] Re: sudden sound loss

[Duncan <1i5t5.duncan@cox.net>]

Raffaele BELARDI <raffaele.belardi@st.com> posted
1207924415.6155.35.camel@ws2912.agr.st.com, excerpted below, on  Fri, 11
Apr 2008 16:33:35 +0200:

> Actually it's the ADC/DAC that performs the mixing (the AD1986A in this
> case). I checked the chip specs, it supports spreading 2ch over 6ch so
> probably the feature is not yet supported by ALSA. Also some search in
> the Gentoo forums confirm this
> (http://forums.gentoo.org/viewtopic-t-414308-postdays-0-postorder-asc-
start-25.html)

In parallel with the other reply (which I was going to reply to but hit 
the wrong key and deleted instead, sorry) suggesting jack, AFAIK, ALSA 
does have software mixing for this sort of thing as well, but it involves 
rather "deeper magic" with the various plugins than I've ventured into, 
myself.  It's apparently extremely flexible -- if you know how to setup 
the plugins in the right order, output of one into the input of the next, 
etc.  

There ought to be documentation out there for it and I've always been 
going to look into it, but then I got a 5.1 Onkyo amp and now just use 
its surround mixing and send the standard two-channel out the digital PCM 
out on the computer, via the coax, to the digital PCM coax input on the 
Onkyo.  I figure it's about the same anyway, since the source I'm playing 
is two-channel stereo to begin with.  Except, if I really knew what I was 
doing, doing it in software on the computer side would probably give me 
rather more flexibility, but doing it on the Onkyo has been "good 
enough", and offloads those extra CPU cycles compared to doing it in 
software on the computer, as well.

BTW, the going opinion (at least the going opinion on /. whenever a 
computer audio article comes up, however you judge /that/ opinion) is 
that it's basically impossible to get good quality on-computer sound no 
matter /what/ board you have in the computer, simply because there's too 
much electrical noise in there.  Not that it's going to matter on say 128 
kbps MP3s or cheap computer speakers anyway, but for good recording or 
decent quality source and playback over a decent system, the 
recommendation is to NOT do the DAC in-computer, but either use digital-
out (even on the built-in sound) and an external amp (as I'm doing now), 
or one of those USB or firewire based soundcards, thus getting the DAC 
out of the computer case and into its own somewhat more electrically 
isolated environment.

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman

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