I've created a simple output plugin which uses WASAPI, so it can be used on Windows Vista or later.
It's only a first version, and it can be downloaded on my website:
I know that there already was a WASAPI output plugin, but it didn't really function the way I wanted.
My plugin currently prefers exclusive mode, but if it fails to find a suitable exclusive mode, it will connect in shared mode.
It can do high quality resampling if required, and supports 16,24 and 32-bit outputs.
For input files it currently only supports 16 and 32 bit files.
Volume-changes are always click-less.
Currently it also prefers a low latency, but if it detects a problem with glitches in the output it will automatically increase the latency. Since it doesn't remember the optimal setting yet, this means that when you first start winamp there might be a few glitches the first few minutes you use it.
The reason I created it was because my laptop doesn't want to play audio without glitches in directsound mode, but it does play without glitches in exclusive wasapi mode, and with only very infrequent glitches in wasapi shared mode.
An advantage of exclusive mode is also that you aren't interrupted by other programs (annoying flash popups in your browser for example
Some things that I might add to it in the future:
-Not close wasapi immediately when close is called so that it responds faster when loading another song
-Remember optimal latency
-Configuration for exclusive mode and latency
-Up- and down-converting for 5.1 to 2.0 or 2.0 to 5.1 (maybe with bass-redirection also)
-Support for 24-bit input files
If anyone is interested in trying it, or wants to make suggestions, feel free to do so!