Optical sound output causing lag in games (GTA:SA)

[Salmonella]

So I've been using the optical sound output of my motherboard for a while now, and everything is fine as long as you play the game with either GTA:SA sound on, or off. When you listen to .wav files in a playback program (I use MediaMonkey) this causes lag ingame, it gets worse over time. I usually listen to music with ''Exclusive Mode'' in the WASAPI plugin on, which means the sound is streamed directly to the output (which for me is the optical output) and blocks other applications sound.

With this 'exclusive mode' turned on, the lag is even worse, eventually dropping to 0.5FPS after 5 minutes of playing. I have talked about this ingame and I found out that I'm not the only one with the problem, because @Traser has encountered the exact same problem. It's not hardware related either, because I had it on my previous motherboard too and have since swapped out all the hardware.

I have the same problem when I run TeamSpeak while playing GTA:SA, except Teamspeak seems to inflict a lot less damage on my performance, causing it to drop to only 40FPS instead of below 5 when a high quality audio source is streamed. I installed all drivers manually too.

Does anyone have any idea how I could fix this interference between the games I play and optical audio?

For those who don't know what optical audio is, it's on most motherboards and looks something like this.

[Janar]

Just GTA:SA or other games also?
(seems like SPDIF port on the picture)

[Salmonella]

Well, I don't have a lot of other games to test, but it doesn't seem to be affecting Minecraft or GTA:VC

[Traser]

Something to do with the plugins? (codecs) maybe.

[Salmonella]

It's not the plugin or codec of my music program, because it does the same with TeamSpeak.

So yesterday I tried it in Minecraft as well. No performance drop there.

It seems to be just in GTA:SA.

[TheRock]

GTA:SA is an outdated game.. Minecraft is developed even today..

Try GTA:SA with V1 update (The one that doesn't play with SA-MP) and see if it plays there, then it's game based error.

[Salmonella]

Nah, didn't change anything.

I don't think it has anything to do with the age of the game. Vice City runs fine. It's just some kind of weird interference between GTA:SA and my sound streaming through an optical output.

[Fuzzy]

GTA SA uses EAX Advanced HD4, while GTA VC uses HD3, so maybe the issue could be in that? Not that you can do anything about it I guess.