Vorbis - Nov 2001 - ATTENTION Re: Multichannel files

I noticed that my previous message is not very complete so I send here an
"enhanced
version". Please disregard the old one an reply to this one only. ( you can
delete
the ATTENTION word from subject )

Wilson (defiler@null.net) wrote :
 
> There are two ways to decode multi-channel audio. In hardware, or in 
> software. 
> Hardware: A receiver or processor takes a Dolby Digital (for example)
stream
> and converts it into something your amps/speakers are interested in. 
> Software: Your PC decodes a 5.1 audio stream into six discrete audio
streams
> and passes them to analog output. 
> 
> Sound cards that can handle what is described in the second case are fairly
> rare. The Hercules Game Theatre XP, the M-Audio Delta Theatre ($$$), etc. 
I have a 4 year old 4 channel sound card ( Ensoniq AudioPCI , 20 USD ).
Almost all newer cards support 5.1 output, like the SB Live! 5.1 series.
That is 6 analog outputs.
A Live! Player 5.1 is 40 USD here at my place.
> Most people don't have them. Doing real 5.1 output from the PC without
a
> receiver that locks you into Dolby Digital is either expensive (full
pre/pro
> combo)
There was a surround amplifier available for 1000 ATS in Austria recently.
That is cca. 64 USD. It has 4(6) analog inputs and can drive four speakers
( it has 4 amplifiers ). You need another normal 2 channel amplifier to get
an 5.1 setup. I believe it also has a Dolby ProLogic decoder, but that is not
of interest to us. Is has about 50 Watts power per speaker.

Or you could use 3 normal stereo amplifiers. I also believe most newer
"movie"
or AV amplifiers have 6 channel analog input too.
> or rare (analog 5.1 multimedia speakers with LFE management. Hard to 
> come by.) 
Creative/Cambridge SoundWorks DeskTop Theater™ 5.1 DTT2200 : 128 euro ~= 112 USD
It about 156USD in Slovenia.

It can be bought in any computer shop.
> To play a multi-channel Ogg file through a receiver, the receiver would
have
> to directly support Ogg, and the sound card drivers would have to support 
> pushing the Ogg through Toslink or S/PDIF. An alternative is to transcode 
> the Ogg output on the fly into AC-3 for transport, but then we're not 
> patent-free anymore. 
Just decode to 6 independent channels and send them thru the analog outputs
of the 5.1 sound card.

 
> Either there's something I'm missing, or I don't see much of a
use for 5.1
> Oggs. 
Now if someone wrote a program that uses 4 four channels of my AudioPCI and
the 2 of the on-board sound to get 5.1 , that would be cool :-)


-- 
David Balazic
--------------
"Be excellent to each other." - Bill S. Preston, Esq., &
"Ted" Theodore Logan
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

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On Thu, 15 Nov 2001, David Balazic wrote:
> > Either there's something I'm missing, or I don't see much
of a use for 5.1
> > Oggs. 
> 
> 
> Now if someone wrote a program that uses 4 four channels of my AudioPCI and
> the 2 of the on-board sound to get 5.1 , that would be cool :-)
I just wanted to point out that this would not work too well after a while
because of clock-drift between the two cards.  The oscillators on the cards
will slowly get out of sync, and the audio will drift out of phase, ruining
the surround sound image.  That's why you need all of the decoders on the
same
card (where presumably there is a single clock), or you need an expensive card
that can take an external clock input (which is what they do in recording
situations).


---
Stan Seibert

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----- Original Message -----
From: "David Balazic" <david.balazic@uni-mb.si>
To: <defiler@null.net>; <vorbis@xiph.org>
Sent: Thursday, November 15, 2001 8:45 AM
Subject: ATTENTION Re: [vorbis] Multichannel files
> I noticed that my previous message is not very complete so I send here an
"enhanced
> version". Please disregard the old one an reply to this one only. (
you
can delete
> the ATTENTION word from subject )
>
> Wilson (defiler@null.net) wrote :
>
> > There are two ways to decode multi-channel audio. In hardware, or in
> > software.
> > Hardware: A receiver or processor takes a Dolby Digital (for example)
stream
> > and converts it into something your amps/speakers are interested in.
> > Software: Your PC decodes a 5.1 audio stream into six discrete audio
streams
> > and passes them to analog output.
> >
> > Sound cards that can handle what is described in the second case are
fairly
> > rare. The Hercules Game Theatre XP, the M-Audio Delta Theatre ($$$),
etc.
>
> I have a 4 year old 4 channel sound card ( Ensoniq AudioPCI , 20 USD ).
> Almost all newer cards support 5.1 output, like the SB Live! 5.1 series.
> That is 6 analog outputs.
> A Live! Player 5.1 is 40 USD here at my place.
>
Actually, the Audigy (replaces the Live!) lets you do EITHER discrete
subwoofer OR discrete center in analog mode.
http://www.3dsoundsurge.com/reviews/AudigyEI/Audigy-p2.html
In other words, it doesn't do what we need. All the SB cards are geared
toward 5.1 output via S/PDIF / Whatever to a receiver/decoder.
> > Most people don't have them. Doing real 5.1 output from the PC
without a
> > receiver that locks you into Dolby Digital is either expensive (full
pre/pro
> > combo)
>
> There was a surround amplifier available for 1000 ATS in Austria recently.
> That is cca. 64 USD. It has 4(6) analog inputs and can drive four speakers
> ( it has 4 amplifiers ). You need another normal 2 channel amplifier to
get
> an 5.1 setup. I believe it also has a Dolby ProLogic decoder, but that is
not
> of interest to us. Is has about 50 Watts power per speaker.
I meant expensive for quality equal to a cheap 5.1 receiver. I don't mean to
insult a $64 amp, so I won't say anything about it. :)
>
> Or you could use 3 normal stereo amplifiers. I also believe most newer
"movie"
> or AV amplifiers have 6 channel analog input too.
Yes, many do have 6 analog channels.. Again, the trick is getting 6-channel
analog output from your PC.
Also, these things are expensive.
>
> > or rare (analog 5.1 multimedia speakers with LFE management. Hard to
> > come by.)
>
> Creative/Cambridge SoundWorks DeskTop TheaterT 5.1 DTT2200 : 128 euro ~112
USD
> It about 156USD in Slovenia.
>
The DTT2200 does not offer 6 discrete channels. Yes, it accepts analog
inputs, but not 6 of them. Thus, you don't have a true center channel or
LFE.
Here's a (crappy) photo of the connector panel I found on the net. See? The
DTT2200 appears to generate a matrixed center channel from the left and
right channels.
http://www.tech-gods.com/reviews/227/busysub.jpg
> It can be bought in any computer shop.
>
> > To play a multi-channel Ogg file through a receiver, the receiver
would
have
> > to directly support Ogg, and the sound card drivers would have to
support
> > pushing the Ogg through Toslink or S/PDIF. An alternative is to
transcode
> > the Ogg output on the fly into AC-3 for transport, but then we're
not
> > patent-free anymore.
>
> Just decode to 6 independent channels and send them thru the analog
outputs
> of the 5.1 sound card.
>
> Now if someone wrote a program that uses 4 four channels of my AudioPCI
and
> the 2 of the on-board sound to get 5.1 , that would be cool :-)
>
Yes, that would be cool. Just get two "4 speaker" sound cards, and
you'd
support all 6 speakers. Not exactly a mainstream concept, though.

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