[vorbis] Multichannel files

[Wilson]

----- 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
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.

--- >8 ----
List archives:  http://www.xiph.org/archives/
Ogg project homepage: http://www.xiph.org/ogg/
To unsubscribe from this list, send a message to 'vorbis-request at xiph.org'
containing only the word 'unsubscribe' in the body.  No subject is needed.
Unsubscribe messages sent to the list will be ignored/filtered.