Emulator

What's the problem?
When you play a 2 player game (for example Wii Sports or Mario Kart Wii) using the split-screen, with framelimit on auto, on 60 (NTSC), or off but with audio throttle on, the fps are limited to 30 (still showing 100% speed though), instead of the 60 of single player mode (before anyone asks, these two games are supposed to run at 60 fps;-)).
The problem is not due to a slowdown, because my system can handle 50 fps even in split-screen (in Mario Kart Wii something less), the problem here is that fps are beeing limited by the emulator more than they should (more than real speed).
In fact it is like the emulator calculates a frame limit of 30 for each player screen (or window as you like) then "adding" the two windows (30 + 30) comes to think that it is still using 60fps...

Dolphin version with the problem (as it appears in the title bar, Ex.: "R
4779" or "R 6403M"):
r6558 (but couldn't find r6555, r6556 and r6557 build to test, so I cannot tell if they're broken too...)

(optional) Dolphin version that does not have the problem:
r6554

Operating system and version:
32-bit or 64-bit:
Windows XP SP3 32bit, Intel e8400, Ati hd4850 with both OpenGL and Dx9 plugin, two real wiimotes

Game ID (as it appears in game properties, Ex.: "GZ2P01" or "RSBE01"):
RSPE01 (Wii Sports) and RMCP01 (Mario Kart Wii)

Build command-line (not on Windows):

Was the ISO a plain dump from disc, compressed and/or scrubbed?
Plain dump

Please provide any additional information below.
In single player the emulator shows 60fps - 60 vps - 100% speed, in split screen it shows 30fps - 60 vps - 100% speed (but plays half speed).
In split-screen if I set the framelimit and audio throttle to off, or put framelimit to 60 and use "use fps for limiting", the "stolen" fps come back and I am able to play at 50 fps (of course still not full speed because of the more power requested by the split-screen, but way better than 30 fps), anyway in this way the emulator shows vps 110 and speed 180% (while in r6554 with split-screen I get 50 fps 50 vps and 83% speed with or without framelimit).
Don't know yet if some other game is affected as well...