Mercury is implemented mainly in C++ (compiles in C++14 mode). Currently runs on Linux and Windows. Compilation is tested on Linux (gcc / glibc toolchain) and Windows (Mingw64 posix toolchain). ALSA ...
Even with REAL, the osu's playback latency is still about 25ms. Anyway this is the easiest way to gain such improvement. Tools like osu-External-ASIO-Sound or AsioHookForOsu gives ASIO support, but ...