Subject: Re: [linux-audio-dev] suggestion for developers: "real" quad-channel output on an SBlive
From: D. Stimits (stimits_AT_idcomm.com)
Date: Thu Nov 22 2001 - 01:35:13 EET
"STEFFL, ERIK *Internet* (SBCSI)" wrote:
>
> > -----Original Message-----
> > From: D. Stimits [mailto:stimits_AT_idcomm.com]
> > Sent: Wednesday, November 21, 2001 11:17 AM
> > To: linux-audio-dev_AT_music.columbia.edu
> > Subject: Re: [linux-audio-dev] suggestion for developers: "real"
> > quad-channel output on an SBlive
> >
> >
> > "STEFFL, ERIK *Internet* (SBCSI)" wrote:
> > >
> > > > -----Original Message-----
> > > > From: Josh Whiting [mailto:jwhiting_AT_hampshire.edu]
> > > >
> > > > i am a list-lurker, primarily a windows multimedia user,
> > but with an
> > > > interest in audio software development and hence an
> > interest in linux.
> > > >
> > > > anyway, i have and idea that has been provoked by my recent
> > > > explorations
> > > > into quad-channel audio output. Basically, the idea is to
> > > > write a driver to
> > > > interface with the SB-Live EAX bus that converts the SB
> > live into a
> > > > more-or-less 'true' four channel output device. How? 1 -
> > > > setup two stereo
> > > > virtual audio input ports, 2 - assign each channel a status
> > > > in the EAX bus
> > > > as a sound source with a specific spatial position so as to
> > > > emulate the
> > > > direct dispatch of each channel to its respective output in
> > > > the dual-output
> > > > SB live DACs. You may not even need two virtual ports,
> > as you could
> > > > probably assign the main output (sb live wave out) to the
> > front stereo
> > > > outputs and then just send the second (virtual) stereo stream
> > > > to the rear
> > > > outputs.
> > > >
> > > > and bam - the SB live is now a (low cost) four channel
> > output device,
> > > > overcoming the (idiotic, painful) limitations imposed by
> > creative's
> > > > engineering of the board only support a single stereo output
> > > > even though the
> > > > card has two of them...
> > >
> > > ?
> > >
> > > sb live provides 5.1 output under windows (you can set
> > output under
> > > speakers in eax control center (headphones, two speakers, 4
> > speakers, 5.1
> > > speakers), there's also a demo for that somewhere there).
> > Not sure how it
> > > works under linux (I don't have linux installed on that
> > computer yet).
> >
> > EAX is proprietary. It isn't available under Linux, and
> > unlikely it ever
> > will. The OpenAL code is probably the closest you'll see in the near
> > future, but something of a similar idea could probably be used there
> > (just not EAX).
>
> aha. but if eax can do it then there has to be hw that supports it, right?
> otherwise eax would be able to output 5 separate channels (and it does, even
> though I don't know how well separated they are). the original post was
> talking about more-or-less true 4 channel and I was saying that 5 channel
> output is possible (using sb live HW, there might be software issues
> involved that are not easy to solve).
>
> or are you saying that using information available to opensource
> developers it is not possible to use the same HW that eax uses?
Nope, I'm saying that you're in a losing battle if you want to use EAX
as the starting point. The guy to ask about how well separated (and
whether the hardware is capable of) 4 channel and 5 channel output would
be Daniel Bertrand, the emu10k1 "main dude guy". See:
emu10k1-devel_AT_opensource.creative.com
And:
d.bertrand_AT_ieee.org
Once you know the hardware is capable of doing what you want, you have a
choice of either using some API like EAX (likely OpenAL), or working at
the deepest levels of hardware (not what the original idea had
suggested, the original idea seems to have referred to a simple way of
coming close to distinct channels without working at the hardware
level). So if the hardware can do what is wanted, probably talking to
one of the OpenAL gurus would be the next step, finding out if it can do
what was suggested with EAX. In that case, probably see newsgroup
news.lokigames.com.
D. Stimits, stimits_AT_idcomm.com
>
> erik
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