Better WASAPI audio resampler?

[slouken]

@cgutman said in #4604:
WASAPI does actually have a proper resampler available via AUDCLNT_STREAMFLAGS_AUTOCONVERTPCM and AUDCLNT_STREAMFLAGS_SRC_DEFAULT_QUALITY documented here. I've confirmed it works at least back to Windows 7 (haven't tried Vista).

We should evaluate whether this resampler has better performance or quality than SDL's built-in resampler.

[sezero]

@slouken: ac32c52 results in build errors with older SDKS. See:
https://buildbot.libsdl.org/#/builders/20/builds/559

FAILED: CMakeFiles/SDL2-static.dir/src/audio/wasapi/SDL_wasapi.c.obj 
C:\PROGRA~1\CMake\bin\ccache.exe  x86_64-w64-mingw32-gcc.exe -DUSING_GENERATED_CONFIG_H -Iinclude -I../include -idirafter "C:/buildbot/worker/SDL/sdl-mingw-amd64/src/src/video/khronos"  "-IC:/buildbot/worker/SDL/sdl-mingw-amd64/src/src/hidapi/hidapi" -msse3 -msse2 -msse -m3dnow -mmmx -Wshadow -fvisibility=hidden -Wdeclaration-after-statement -Werror=declaration-after-statement -fno-strict-aliasing -Wall  -Os -DNDEBUG -MD -MT CMakeFiles/SDL2-static.dir/src/audio/wasapi/SDL_wasapi.c.obj -MF CMakeFiles\SDL2-static.dir\src\audio\wasapi\SDL_wasapi.c.obj.d -o CMakeFiles/SDL2-static.dir/src/audio/wasapi/SDL_wasapi.c.obj   -c ../src/audio/wasapi/SDL_wasapi.c
../src/audio/wasapi/SDL_wasapi.c: In function 'WASAPI_PrepDevice':
../src/audio/wasapi/SDL_wasapi.c:561:25: error: 'AUDCLNT_STREAMFLAGS_AUTOCONVERTPCM' undeclared (first use in this function); did you mean 'AUDCLNT_STREAMFLAGS_LOOPBACK'?
         streamflags |= (AUDCLNT_STREAMFLAGS_AUTOCONVERTPCM | AUDCLNT_STREAMFLAGS_SRC_DEFAULT_QUALITY);
                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
                         AUDCLNT_STREAMFLAGS_LOOPBACK
../src/audio/wasapi/SDL_wasapi.c:561:25: note: each undeclared identifier is reported only once for each function it appears in
../src/audio/wasapi/SDL_wasapi.c:561:62: error: 'AUDCLNT_STREAMFLAGS_SRC_DEFAULT_QUALITY' undeclared (first use in this function); did you mean 'AUDCLNT_STREAMFLAGS_RATEADJUST'?
         streamflags |= (AUDCLNT_STREAMFLAGS_AUTOCONVERTPCM | AUDCLNT_STREAMFLAGS_SRC_DEFAULT_QUALITY);
                                                              ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
                                                              AUDCLNT_STREAMFLAGS_RATEADJUST

AUDCLNT_STREAMFLAGS_AUTOCONVERTPCM and AUDCLNT_STREAMFLAGS_SRC_DEFAULT_QUALITY
must be defined if not already defined, e.g. like:

#ifndef AUDCLNT_STREAMFLAGS_SRC_DEFAULT_QUALITY
#define AUDCLNT_STREAMFLAGS_SRC_DEFAULT_QUALITY 0x08000000
#endif
#ifndef AUDCLNT_STREAMFLAGS_AUTOCONVERTPCM
#define AUDCLNT_STREAMFLAGS_AUTOCONVERTPCM      0x80000000
#endif

I don't know whether the resulting dll will be compatible with win8x and older.

[sezero]

OK, I went ahead and pushed ed6eb07

Still don't know whether the resulting dll will be compatible with win8x and older, though.