Multichanel audio over SPDIF

[dentaku]

Ive got a 5.1 receiver with optical and digital coax inputs but it dosent have the multichanel analog ones. I know I cant get true discrete 5.1 over optical unless I use a soundstorm motherboard, but on a sound card with digital out can games pass a 2 channel prologic signal to be decoded by the reciever for surround sound in games?

 

[Mister X]

but on a sound card with digital out can games pass a 2 channel prologic signal to be decoded by the reciever for surround sound in games?

No.
The SPDIF interface on your card will only output two channels of PCM data, or pass through a previously encoded DD signal.
That is all.
Any other form of Pseudo multichannel matrixing is handled entirely by your receiver.


This is the exact distinction I was attempting to make in that other thread.... and for this exact reason.

 

[SilverMK3]

Your soundcard will send a clean 2 channel, stereo PCM signal to your receiver. Your receiver will then matrix it to 5.1 via Pro Logic, Pro Logic II, Logic 7, or whatever options you have available.

 

[King Og]

Originally posted in another thread:

I have read through countless forums online and seem to not be able to find exactly what I'm looking for or I'm finding conflicting information, so I'll just ask here and see if anyone can help. I just got a Shuttle SN45GV2 system (which has the NForce 2 Ultra 400, but I can't figure out if it's actually Soundstorm-equipped as Shuttle's documentation is not the best) and I want to get a new set of speakers to replace the old Klipsch 4.1 Promedia's which died. My question is whether I can directly connect the SPDIF optical-out connections on the back of the Shuttle straight into the optical-in jacks on the Logitech Z-5500 speakers and still get 5.1 sound? I don't have a receiver or anything else doing processing on this signal, I just want a clean Shuttle-Speaker connection.

 

[SilverMK3]

Your system is SoundStorm capable, because it has the nVidia MCP-T southbridge and an SPDIF out. This means that it can automagically encode your audio content into a Dolby Digital 5.1 stream that can be understood by home-theater receivers and digital speakers.

The logitech Z-5500's have a built-in decoder that can handle a Dolby Digital stream so, yes, you're all set to go.

 

[dentaku]

No.
The SPDIF interface on your card will only output two channels of PCM data, or pass through a previously encoded DD signal.
That is all.
Any other form of Pseudo multichannel matrixing is handled entirely by your receiver.


This is the exact distinction I was attempting to make in that other thread.... and for this exact reason.

I understand this, I dont really care what encodes or decodes what, I just want to know with this setup If sounds will come out of all of the speakers when I am playing games.

 

[ncantador]

I dont really care what encodes or decodes what, I just want to know with this setup If sounds will come out of all of the speakers when I am playing games.

In short the answer to your question above is yes,

However you should check out this thread. There was a pretty lively discussion on this subject.

http://www.hardforum.com/showthread.php?t=822162

 

[Mister X]

I understand this, I dont really care what encodes or decodes what

That is not what you said before.....the question was:

but on a sound card with digital out can games pass a 2 channel prologic signal to be decoded by the reciever for surround sound in games?

You was asking about encoding then you don't care about it?
I don't get it.

The distinction here is......pro logic is not a encoded multichannel audio format.

And the answer is still NO.
Your sound card does not/cannot encode a pro logic signal.
Prologic matrixing is handled entirely by the receiver.

Geeze.... I just typed the same answer all over again.

 

[DrT]

Actually, it can - though I believe only through software or plugins. Pro Logic is just a way to "hide" a 4-channel signal in the space of 2 stereo channels; the algorithms are out there, and you can do it in real time. You can get plugins that will do it for most popular media players, though that's rather useless unless you happen to have a collection of 5.1 music or video files.

Since the Pro Logic signal is just stereo, it can easily be passed through any digital connection as 2-channel PCM and then matrixed by a receiver into a multichannel format.

You could theoretically do the encoding in a system-wide way; all your sounds, including games, could be translated into Pro Logic. This could be done in sound card drivers or with a third party directsound app, but I don't know which cards or what app that would be.

 

[ncantador]

The signal souce is 2channel, the output is 5, low frequencies are mixed from the 2 front channels, and sent to the sub on 5.1 speakers systems when a subwoofer is present.

Here is the link to dolby labs that explains the technology in a simplified manner.

http://www.dolby.com/consumer/technology/prologic_II.html

Actually, it can - though I believe only through software or plugins. Pro Logic is just a way to "hide" a 4-channel signal in the space of 2 stereo channels

This is true, I don't know of any hardware or software plugin that would do this, but dolby, and several game developers that have testimonials on their site, say they have encoded in ProLogic . It's easier to find encoded material (such as games with the dolby surround logo), though its not required.