Help me understand Digital 5.1 over Optical (Toslink)

[Zaskar]

Ok I just upgraded my Old Creative 4 speaker setup to a Logitech Z-5500 and decided to use an Optical Toslink cable to connect it to my EVGA 790i's Realtek onboard sound.

I noticed that no longer do I have the options to choose speaker settings like 2.1, 4.1, 5.1, etc. And All Audio is just stereo sound using just the 2 side speakers unless I change the mode on my speaker console to "Dolby Pro logic for Movies" or "Dolby Pro logic for Music".

When I do this it seems to be real surround sound in games like CS, but what does this mean? Can I only now get "real" surround sound in games that support Dolby encoding? Will older EAX based games no longer have real surround sound compared to using front and rear analogue cables?

Do all games support this, and if not is the sound coming from all 5 speakers just cloned stereo sound or decoded in a way where the audio controller in the speakers sends audio where it thinks it should go but might not be correct compared to using analogue cables on a game that supports 5.1 like that?

I use Vista, so for older EAX games I needed to add them to Realtek's Soundback program (Like Creative's Alchemy), which let it use EAX to get surround sound, I noticed now with the Dolby enabled it still has surround sound in those games (well, sound is coming from all speakers atleast), should I still be adding those games to the Soundback programs list for EAX? Is it doing anything now?

This just surprise me, wasn't expecting that speaker control through the software would be lost with Digital, so just looking for a bit of clarification :D

1 last thing I'm noticing, sometimes on new sounds it cuts off the first fraction of a second, like then clicking windows volume control and changing the volume, the "ding" it makes sometimes has the first fraction of it cut off (with speakers set to PLII (I assume Dolby Pro Logic 2) it usually cuts off the entire "ding" but the display on the console says it received a digital signal), noticed it every so often in CS on gun shots, sometimes the first gunshot sound has the first fraction cut off. Wasn't like that with analogue. Just wondering about that.

Thanks guys.

[lowfat]

Unless some sort of compression (Dolby Digital/AC3 or DTS) is used, optical/SPDIF is always 2 channels. If you wanted to get 5.1 over optical you will need a soundcard that can encode either DD or DTS. I have no idea if there is an option on 790i's onboard sound that can do this. Almost all Intel chipsets can, so maybe Nvidia used a codec that can.

When you are selecting Dolby Pro Logic, it is just simulating surround sound. It isn't all that bad, but definitely won't get the channel separation you would with discrete 5.1.

[ToTTenTranz]

In order to have 5.1 through optical, you must turn on Dolby Digital Live or DTS Connect in the codec's driver, which you found out already.

However, you'll only have 5.1 sound when the soundsource has 5.1 channels. This means you'll only hear 5.1 in 5.1-enabled movies like DVD and some AVI/MKV (where you don't even need to activate DDLive), in games and in DVD-Audio. If the soundsource is in stereo, you'll only hear the front left and right speakers.
This is, unless you're using some sort of upmixing to turn stereo sources into surround ones. I don't know if Realtek's drivers have this.
Your 4 speaker setup used to have sound in all speakers and in all occasions probably because you had CMSS (Creative multi-speaker surround) turned on.

[Zaskar]

In order to have 5.1 through optical, you must turn on Dolby Digital Live or DTS Connect in the codec's driver, which you found out already.

However, you'll only have 5.1 sound when the soundsource has 5.1 channels. This means you'll only hear 5.1 in 5.1-enabled movies like DVD and some AVI/MKV (where you don't even need to activate DDLive), in games and in DVD-Audio. If the soundsource is in stereo, you'll only hear the front left and right speakers.
This is, unless you're using some sort of upmixing to turn stereo sources into surround ones. I don't know if Realtek's drivers have this.
Your 4 speaker setup used to have sound in all speakers and in all occasions probably because you had CMSS (Creative multi-speaker surround) turned on.

Oh thats how it was like before, only had surround sound when the source had it :D Thats exactly what I'm looking for (if its stereo and I really want surround I guess I could just enable PLII in the speakers)

Thanks for your help guys, it unfortunately seems that the EVGA 790i (reference design) board doesn't have DDL or DLP :/ So I either have to get a new sound card or switch back to analogue for now till I either get a sound card or a new motherboard.

[Etihtsarom]

I believe that using Toslink or coaxial will give you surround sound if the material (i.e. movie, game, music) has 5.1 output. Failing this, you will get stereo sound unless you use "virtual surround sound". Virtual surround sound will just split the signal from the front speakers and send them to the other channels as well. Most modern motherboard should have that feature with onboard sound, but if not, you would have to buy a sound card. :(