Convert float samples to integer using a power-of-2 multiple

2 files changed, 17 insertions, 19 deletions

diff --git a/Alc/ALu.c b/Alc/ALu.c
index f0e4d735..710b64be 100644
--- a/Alc/ALu.c
+++ b/Alc/ALu.c
@@ -1306,34 +1306,30 @@ static void UpdateContextSources(ALCcontext *ctx, const struct ALeffectslotArray
 }
 
 
-/* Specialized function to clamp to [-1, +1] with only one branch. This also
- * converts NaN to 0. */
-static inline ALfloat aluClampf(ALfloat val)
-{
-    if(fabsf(val) <= 1.0f) return val;
-    return (ALfloat)((0.0f < val) - (val < 0.0f));
-}
-
 static inline ALfloat aluF2F(ALfloat val)
 { return val; }
 
+#define S25_MAX_NORM (16777215.0f/16777216.0f)
 static inline ALint aluF2I(ALfloat val)
 {
-    /* Floats only have a 24-bit mantissa, so [-16777215, +16777215] is the max
-     * integer range normalized floats can be safely converted to.
+    /* Floats only have a 24-bit mantissa, so [-16777216, +16777216] is the max
+     * integer range normalized floats can be safely converted to (a bit of the
+     * exponent helps out, effectively giving 25 bits).
      */
-    return fastf2i(aluClampf(val)*16777215.0f)<<7;
+    return fastf2i(clampf(val, -1.0f, S25_MAX_NORM)*16777216.0f)<<7;
 }
 static inline ALuint aluF2UI(ALfloat val)
 { return aluF2I(val)+2147483648u; }
 
+#define S16_MAX_NORM (32767.0f/32768.0f)
 static inline ALshort aluF2S(ALfloat val)
-{ return fastf2i(aluClampf(val)*32767.0f); }
+{ return fastf2i(clampf(val, -1.0f, S16_MAX_NORM)*32768.0f); }
 static inline ALushort aluF2US(ALfloat val)
 { return aluF2S(val)+32768; }
 
+#define S8_MAX_NORM (127.0f/128.0f)
 static inline ALbyte aluF2B(ALfloat val)
-{ return fastf2i(aluClampf(val)*127.0f); }
+{ return fastf2i(clampf(val, -1.0f, S8_MAX_NORM)*128.0f); }
 static inline ALubyte aluF2UB(ALfloat val)
 { return aluF2B(val)+128; }
 
diff --git a/OpenAL32/sample_cvt.c b/OpenAL32/sample_cvt.c
index 22f2e898..89c2a408 100644
--- a/OpenAL32/sample_cvt.c
+++ b/OpenAL32/sample_cvt.c
@@ -574,9 +574,10 @@ static inline ALfloat Conv_ALfloat_ALuint(ALuint val)
 #define DECL_TEMPLATE(FT, T, smin, smax)        \
 static inline AL##T Conv_AL##T##_##FT(FT val)   \
 {                                               \
-    if(val > 1.0f) return smax;                 \
-    if(val < -1.0f) return smin;                \
-    return (AL##T)(val * (FT)smax);             \
+    val *= (FT)smax + 1;                        \
+    if(val >= (FT)smax) return smax;            \
+    if(val <= (FT)smin) return smin;            \
+    return (AL##T)val;                          \
 }                                               \
 static inline ALu##T Conv_ALu##T##_##FT(FT val) \
 { return Conv_ALu##T##_AL##T(Conv_AL##T##_##FT(val)); }
@@ -590,9 +591,10 @@ DECL_TEMPLATE(ALdouble, int, -2147483647-1, 2147483647)
 /* Special handling for float32 to int32, since it would overflow. */
 static inline ALint Conv_ALint_ALfloat(ALfloat val)
 {
-    if(val > 1.0f) return 2147483647;
-    if(val < -1.0f) return -2147483647-1;
-    return (ALint)(val * 16777215.0f) << 7;
+    val *= 16777216.0f;
+    if(val >= 16777215.0f) return 0x7fffff80/*16777215 << 7*/;
+    if(val <= -16777216.0f) return 0x80000000/*-16777216 << 7*/;
+    return (ALint)val << 7;
 }
 static inline ALuint Conv_ALuint_ALfloat(ALfloat val)
 { return Conv_ALuint_ALint(Conv_ALint_ALfloat(val)); }