[vorbis] Multichannel files

[Wilson]

I stand corrected.
Obviously my comments about "expensive" hinged on the idea that the DTT2200
and Live 5.1 couldn't do real 6-channel analog. I should have just looked at
my Live! 5.1 to confirm.
However, I think I still have a very valid point. Even if a popular series
of cards supports 5.1 analog output, most people who have 5.1 systems (even
on their PC) are using an external decoder. (Be it integrated with their
speaker system, or part of a receiver, etc.) Note that the 2200 is pretty
much the only product in the "Desktop Theatre" series that doesn't use a DIN
connection from the Live!/whatever card.
None of these people will be able to listen to 5.1 Oggs without converting
them to something their decoder can handle. Again, barring misconception on
my part.

They accused us of suppressing freedom of expression.
This was a lie and we could not let them publish it.
-- Nelba Blandon, Nicaraguan Interior Ministry Director of Censorship

----- Original Message -----
From: "David Balazic" <david.balazic at uni-mb.si>
To: <defiler at null.net>; <vorbis at xiph.org>
Sent: Friday, November 16, 2001 3:42 AM
Subject: Re: [vorbis] Multichannel files

> Wilson (defiler at null.net) wrote :
>
> Please CC replies to my private email ( click REPLY-ALL or something like
that )
>
> > ----- Original Message -----
> > From: "David Balazic" <david.balazic at uni-mb.si>
> > To: <defiler at null.net>; <vorbis at 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 at 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
>
> A quote from the page :
> "The Digital out/Center-subwoofer can, just like the Live 5.1 card,
> be used for either digital output or when in analog mode as the
> center/subwoofer output."
>
> This page says that it is either :
> - digital out put
> - a combined analog center/subwoofer output. It is a stereo connector.
>   One channel is the Center and the other is the subwoofer.
>
> > In other words, it doesn't do what we need. All the SB cards are geared
>
> Yes it does.
>
> > toward 5.1 output via S/PDIF / Whatever to a receiver/decoder.
>
> Wrong, obviously.
>
> > > > 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. :)
>
> See below "about expensive"
>
> > >
> > > 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.
>
> See below "about 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
>
> Yes, it does.
>
> > inputs, but not 6 of them. Thus, you don't have a true center channel or
LFE.
>
> Yes, it does. Yes, you have.
>
> > 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
>
> On page 11 ( eleven ) of the DT2200 manual ( available at
>
ftp://ftp.europe.creative.com/pub/online_library/speakers/DTT2200_Users_Guid
e/English.pdf )
> it is clear that it has 6 analog inputs.
>
> >
> > > 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.
>
> As volsung said , synchronization is a problem. Maybe checking the
position
> ( most card support sample accurate position report of the current played
sample,
> AFAIK ) and dropping samples on the faster DAC ?
> It is probably a difficult to solve problem, because everyone is avoiding
it
> like the plague :-)
>
> About expensive :
>
> What are you complaining about ? What is expensive , compared to what ?
> A DT2200 speaker + a Live! Player 5.1 is about 180 USD. That is very cheap
> for a 5.1 system if you ask me. It is maybe not hi-fi , but a single hi-fi
> speaker costs that much and you need 6 of them ! And an amplifier ( 100
USD
> minimum ).
>
> --
> David Balazic
> --------------
> "Be excellent to each other." - Bill S. Preston, Esq., & "Ted" Theodore
Logan
> - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
- -
>

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