I currently have a OMEGA striker 7.1 sound card in my computer, and it works very well.
However, recently I just noticed that my games, although set to 5.1 are not actually outputting any sound on my center speaker. I did some research, and learned that my card has Dolby Digital Live, which converts the audio signals coming from my PC automatically in to Dolby Digital sound. I have my sound card connected to a 5.1 Sony digital audio receiver, that fully supports Dolby Digital sound. I was wondering, is there a reason that my games aren't playing full 5.1 sound? On a side note, for some strange reason when I play music in Windows Media Player, it will not be full 5.1 (no center speaker) but when I play the same music with VLC media player, I get full 5.1.
Optical Digital can not transmit (either due to bandwith, or due to lack of a standard 5.1 spec) uncompressed 5.1 signals. Period. As such, output is defaulted to 2.0 PCM, regardless of what you set you're speaker settings to.
The only way to get 5.1 over an optical connection is using Dolby Digital or DTS (both of which are compressed signals, getting around the bandwith issue).
DDL simply encodes whatever is being played into a Dolby Digital signal, which allows for the full 5.1 output. Hence, why DDL is such a major feature for any optical connection. Note, DDL does NOT fill in any blank channels.
Basically: Set you're speaker output to 5.1, and enable DDL in your soundcard drivers, and then you should get full 5.1.