Add "fast" variants for the bsinc resamplers

This simply omits the scale factor from the filter, similar to how up-sampling
does. The consequence of this is less smooth transitions when ramping the
pitch while down-sampling, but otherwise behaves fine.

4 files changed, 14 insertions, 7 deletions

diff --git a/alc/alu.cpp b/alc/alu.cpp
index 86d2789e..5df1c3a2 100644
--- a/alc/alu.cpp
+++ b/alc/alu.cpp
@@ -947,9 +947,9 @@ void CalcNonAttnSourceParams(ALvoice *voice, const ALvoicePropsBase *props, cons
         voice->mStep = MAX_PITCH<<FRACTIONBITS;
     else
         voice->mStep = maxu(fastf2u(Pitch * FRACTIONONE), 1);
-    if(props->mResampler == Resampler::BSinc24)
+    if(props->mResampler == Resampler::BSinc24 || props->mResampler == Resampler::FastBSinc24)
         BsincPrepare(voice->mStep, &voice->mResampleState.bsinc, &bsinc24);
-    else if(props->mResampler == Resampler::BSinc12)
+    else if(props->mResampler == Resampler::BSinc12 || props->mResampler == Resampler::FastBSinc12)
         BsincPrepare(voice->mStep, &voice->mResampleState.bsinc, &bsinc12);
     voice->mResampler = SelectResampler(props->mResampler, voice->mStep);
 
@@ -1277,9 +1277,9 @@ void CalcAttnSourceParams(ALvoice *voice, const ALvoicePropsBase *props, const A
         voice->mStep = MAX_PITCH<<FRACTIONBITS;
     else
         voice->mStep = maxu(fastf2u(Pitch * FRACTIONONE), 1);
-    if(props->mResampler == Resampler::BSinc24)
+    if(props->mResampler == Resampler::BSinc24 || props->mResampler == Resampler::FastBSinc24)
         BsincPrepare(voice->mStep, &voice->mResampleState.bsinc, &bsinc24);
-    else if(props->mResampler == Resampler::BSinc12)
+    else if(props->mResampler == Resampler::BSinc12 || props->mResampler == Resampler::FastBSinc12)
         BsincPrepare(voice->mStep, &voice->mResampleState.bsinc, &bsinc12);
     voice->mResampler = SelectResampler(props->mResampler, voice->mStep);
 
diff --git a/alc/alu.h b/alc/alu.h
index e9858ddb..e2b25556 100644
--- a/alc/alu.h
+++ b/alc/alu.h
@@ -46,7 +46,9 @@ enum class Resampler {
     Point,
     Linear,
     Cubic,
+    FastBSinc12,
     BSinc12,
+    FastBSinc24,
     BSinc24,
 
     Max = BSinc24
diff --git a/alc/converter.cpp b/alc/converter.cpp
index b0efb839..aff1c353 100644
--- a/alc/converter.cpp
+++ b/alc/converter.cpp
@@ -167,9 +167,9 @@ SampleConverterPtr CreateSampleConverter(DevFmtType srcType, DevFmtType dstType,
         converter->mResample = Resample_<CopyTag,CTag>;
     else
     {
-        if(resampler == Resampler::BSinc24)
+        if(resampler == Resampler::BSinc24 || resampler == Resampler::FastBSinc24)
             BsincPrepare(converter->mIncrement, &converter->mState.bsinc, &bsinc24);
-        else if(resampler == Resampler::BSinc12)
+        else if(resampler == Resampler::BSinc12 || resampler == Resampler::FastBSinc12)
             BsincPrepare(converter->mIncrement, &converter->mState.bsinc, &bsinc12);
         converter->mResample = SelectResampler(resampler, converter->mIncrement);
     }
diff --git a/alc/mixvoice.cpp b/alc/mixvoice.cpp
index 58a08ce3..e9e0d8df 100644
--- a/alc/mixvoice.cpp
+++ b/alc/mixvoice.cpp
@@ -161,6 +161,9 @@ ResamplerFunc SelectResampler(Resampler resampler, ALuint increment)
         case Resampler::BSinc24:
             if(increment <= FRACTIONONE)
             {
+                /* fall-through */
+        case Resampler::FastBSinc12:
+        case Resampler::FastBSinc24:
 #ifdef HAVE_NEON
                 if((CPUCapFlags&CPU_CAP_NEON))
                     return Resample_<FastBSincTag,NEONTag>;
@@ -191,7 +194,7 @@ void aluInitMixer()
     if(auto resopt = ConfigValueStr(nullptr, nullptr, "resampler"))
     {
         struct ResamplerEntry {
-            const char name[12];
+            const char name[16];
             const Resampler resampler;
         };
         constexpr ResamplerEntry ResamplerList[]{
@@ -199,7 +202,9 @@ void aluInitMixer()
             { "point", Resampler::Point },
             { "cubic", Resampler::Cubic },
             { "bsinc12", Resampler::BSinc12 },
+            { "fast_bsinc12", Resampler::FastBSinc12 },
             { "bsinc24", Resampler::BSinc24 },
+            { "fast_bsinc24", Resampler::FastBSinc24 },
         };
 
         const char *str{resopt->c_str()};