5.1 and S/PDIF

**dj_stick** · Jul 28, 2004, 06:15 PM

A common misconception is that S/PDIF digital audio signals will provide a 5.1 channel sound.

This is not true.

S/PDIF is a 2 channel stereo format, regardless of the medium (optical or coaxial)

The exception to the rule is when a form of compression is used.

Dolby Digital (AC-3) compresses 6 channel signal into the 2 channel format used by S/PDIF, and can then be read by a decoder.

No soundcard apart from the nForce 2 Soundstorm chip so far can encode AC-3. Therefore if you do not have one of these motherboards, the only way to get 5.1 channel sound over S/PDIF is to play a source that is already encoded in the format, such as a DVD video.

Judas · Jul 28, 2004, 08:28 PM

excellent information..... i've never really used s/pdif... is that the optical port?

**dj_stick** · Jul 28, 2004, 08:55 PM

Quote:

Originally posted by Judas
excellent information..... i've never really used s/pdif... is that the optical port?

yes it can be in the opticle medium aswell as coaxial

DavoNogo · Aug 10, 2004, 02:48 AM

Quote:

Originally Posted by dj_stick

No soundcard apart from the nForce 2 Soundstorm chip so far can encode AC-3. Therefore if you do not have one of these motherboards, the only way to get 5.1 channel sound over S/PDIF is to play a source that is already encoded in the format, such as a DVD video.

the latest version of AC3Filter can encode PCM, AC3, DTS, MPEG Audio and PES (a DVD format) on the fly

exorcism · Aug 11, 2004, 09:39 PM

Quote:

Originally Posted by DavoNogo

the latest version of AC3Filter can encode PCM, AC3, DTS, MPEG Audio and PES (a DVD format) on the fly

Is there anyway to use this technique for playing games in surround?

**dj_stick** · Aug 12, 2004, 06:36 AM

the program should automatically do that… but will increase CPU load - possibly reducing performance in your game

exorcism · Aug 13, 2004, 03:33 PM

Quote:

Originally Posted by dj_stick

the program should automatically do that… but will increase CPU load - possibly reducing performance in your game

Isn't AC3Filter an acm codec/filter or something? As in, use it in windows media player? I don't see how I could use it for a game.

**dj_stick** · Aug 13, 2004, 05:38 PM

afaik AC-3 filter attaches itself to the directsound outputs before it reaches the soundcard, and should work for any directsound application

justarandomuser · Aug 15, 2004, 06:34 PM

This doesn't work for games.

Sadly

Lowfat · Oct 10, 2004, 01:33 PM

Thats why i love my Soundstorm

classic_leon · Oct 10, 2004, 02:57 PM

Yeah,excellent information! I think S/PDIF is now the best solution to 192KHz/24Bit DVD-AUDIO for PC.

**dj_stick** · Oct 10, 2004, 03:03 PM

the S/PDIF medium can't support anything more than 24/96 afaik

classic_leon · Oct 10, 2004, 03:19 PM

If I play 192/24 DVD-AUDIO via S/PDIF to stereo speakers of A2 platinum drive, what will happen? will the speakers hiss? Thanks.

**dj_stick** · Oct 10, 2004, 03:25 PM

no - it will be limited to 24/96 - read the specs for your audigy 2, i'm pretty sure it only says s/pdif output is 24/96 at maximum

classic_leon · Oct 10, 2004, 03:28 PM

I got it. Thank you!
Actually I haven't tred it before. I will go n try to play this using S/PDIF.

bollwerk · Oct 26, 2004, 04:49 PM

So currently, the only way to play games in 5.1 and send the output digitally to a home stereo is with the now-discontinued nVidia SoundStorm?

Why doesn't Soundblaster just license an AC-3 encoder for their S/PDIF output?

**dj_stick** · Oct 27, 2004, 01:33 AM

the hardware has to be powerful enough to support it, and dolby has to licence the technology

siriuz · Dec 21, 2004, 11:47 PM

what about this card ?
sound blaster audigy DE
http://creative.com/products/product...uct=5085&nav=2

the specifications say that it supports "Digital : 6-channel S/PDIF"

**dj_stick** · Dec 21, 2004, 11:51 PM

yes ONLY if the original input signal/source file is 5.1, as this is its AC-3 passthrough mode

EDIT: the digital out jack on the audigy cards uses a 4 pole jack that gives 3 seperate stereo SPDIF connections plus a ground wire, for a total of 6 channels (5.1)

siriuz · Dec 22, 2004, 12:10 AM

ah.. ok.. thanks for the quick reply

so a special cable is needed ?

**dj_stick** · Dec 22, 2004, 12:22 AM

yes, most speaker systems that use that connection however would come with that cable (4 pole 3.5mm jack to 9pin mini-din connector)

siriuz · Dec 22, 2004, 12:25 AM

ahh.. so i guess i'll still need to get a soundstorm to hook up my PC to the home theatre set. thanks a lot

**dj_stick** · Dec 22, 2004, 12:29 AM

yep, either that or use a software ac-3 encoder

Lowfat · Dec 22, 2004, 12:31 AM

how about this soundcard? since it does dolby digital live also.

C-Media CMI8768

**dj_stick** · Dec 22, 2004, 12:40 AM

i don't think it encodes ac-3

DavoNogo · Dec 22, 2004, 02:51 AM

with regards to the digital out jack on the audigy, what it does is send out 3 ANALOG channels for ANALOG sources ie. games and music, and it will output digital ONLY if the source is AC3. so basically it saves having to plug in 4 cables, but remember, analog will still be analog using that cable...

there's hope with the soundstorm2 being a stand alone product... it's very unlikely they'll include it with the nforce4 (amd) or the nforce5 (intel), but don't quote me on that.. nvidia said to expect the unexpected