ATTENTION Re: [vorbis] Multichannel files

[David Balazic]

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.

> 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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