READ BEFORE PROMOTE
Edit: Changed title to fit the topic. the post is talking about ASIO, but WASAPI exclusive mode also works.
To be short, ASIO is a sound protocol that recudes sound output latency. Among all music games I prefer LR2 the best, mostly because LR2 has official ASIO output support. Compared with legacy protocols ASIO could provide a lot better playing experience on music games, not only on recording. Besides sound output latency, ASIO bypasses sound mixing in Windows OS, making the sound more natural (I've found that osu sounds a little bit strange after Windows Vista).
One of my friends (around overall rank #150)happens to be very rich and have MANY professional sound card that support universal ASIO output but still meets the latency. Onboard sound cards don't have official support, but we can use ASIO4ALL to simulate it, and it makes sense.
Recently my friend and I did some recording to find out how long the latency is.
the first one comes from my friend and latter 2 are captured on my own, with 1000hz poll rate mechanical keyboard.
I'm disclaiming that the keyboard input detection is not the main issue. The problem is, how players judge if they successfully hit the circle is by hearing the hitsound (the graphic appears relatively slow), especially among top players, however the hitsounds are not ringing at the exact time. They may feel confused when playing very fast maps.
This is more of my personal request since my playing skill is more based on LR2. However the fact is that not only me could not put up with that "small" latency. Btw, 70ms can make a huge difference at top-tier playing.
I've also tried WASAPI on LR2 but it turned out to be even worse. Not sure if it is LR2's problem.
Edit: Changed title to fit the topic. the post is talking about ASIO, but WASAPI exclusive mode also works.
Audio Stream Input/Output (ASIO) is a computer sound card driver protocol for digital audio specified by Steinberg, providing a low-latency and high fidelity interface between a software application and a computer's sound card. Whereas Microsoft's DirectSound is commonly used as an intermediary signal path for non-professional users, ASIO allows musicians and sound engineers to access external hardware directly.(https://en.wikipedia.org/wiki/Audio_Stream_Input/Output)
To be short, ASIO is a sound protocol that recudes sound output latency. Among all music games I prefer LR2 the best, mostly because LR2 has official ASIO output support. Compared with legacy protocols ASIO could provide a lot better playing experience on music games, not only on recording. Besides sound output latency, ASIO bypasses sound mixing in Windows OS, making the sound more natural (I've found that osu sounds a little bit strange after Windows Vista).
One of my friends (around overall rank #150)
Recently my friend and I did some recording to find out how long the latency is.
the first one comes from my friend and latter 2 are captured on my own, with 1000hz poll rate mechanical keyboard.
I'm disclaiming that the keyboard input detection is not the main issue. The problem is, how players judge if they successfully hit the circle is by hearing the hitsound (the graphic appears relatively slow), especially among top players, however the hitsounds are not ringing at the exact time. They may feel confused when playing very fast maps.
This is more of my personal request since my playing skill is more based on LR2. However the fact is that not only me could not put up with that "small" latency. Btw, 70ms can make a huge difference at top-tier playing.
I've also tried WASAPI on LR2 but it turned out to be even worse. Not sure if it is LR2's problem.
I think this will correct osu!'s accuracy in audio output~. 
