As I've said on many occasions RetroCopy was designed from the start to be multicore/multiCPU friendly. Designing complex multithreaded applications like RetroCopy is quite difficult though.
Whilst adding all the new filtering code I had issues with sound generation in RetroCopy, there were hisses and pops when I was enabling some of the more CPU heavy filters. This shouldn't happen in RetroCopy because the VIDEO and AUDIO are run in their own threads, and they have almost no interaction.
I have been neglecting some of the core work in RetroCopy because it's quite complicated and time consuming working on multithreaded code. But I decided enough was enough, I went into the trenches and reorganized and recoded a big part of it. I've moved nearly all of the windows specific code into their own neat little sections and moved all the non platform specific code into the emulator core. This will help me out later when I make the MAC/LINUX/etc ports.
The issue I was having with sound generation is one that happens when the framerate drops below the refresh rate. The video thread was tying up the audio thread on something it shouldn't be waiting on, so I had to work out a new way of spitting out video updates. I never really saw this behaviour because my CPU is quite fast, however I'm sure this would have caused audio issues for some people in the 3D room. Now I've streamlined the core to make it more snappy, and even if you have a graphics filter which is making you run at 10FPS, the audio should be perfect.
There is one more thing I need to change with the core and that is how input is done. I want input to be in its own thread too instead of tied to the video refresh. This is a little more complicated but I hope to have it completed by tonight. I basically want the input thread to be updated at a ridiculous rate (roughly 250 times a second) so that regardless of the video refresh rate you have a nice input feeling.
Finally here is the new options window that pops up when you press ESCAPE whilst running a game (still being worked on). It allows you to adjust some graphics options and do various other things. I must say with all the changes I've done RetroCopy is starting to resembling a pretty polished application/game/emulator. 
