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.

al/state.cpp

@@ -63,7 +63,9 @@ constexpr ALchar alErrOutOfMemory[] = "Out of Memory";
 constexpr ALchar alPointResampler[] = "Nearest";
 constexpr ALchar alLinearResampler[] = "Linear";
 constexpr ALchar alCubicResampler[] = "Cubic";
+constexpr ALchar alFastBSinc12Resampler[] = "11th order Sinc (fast)";
 constexpr ALchar alBSinc12Resampler[] = "11th order Sinc";
+constexpr ALchar alFastBSinc24Resampler[] = "23rd order Sinc (fast)";
 constexpr ALchar alBSinc24Resampler[] = "23rd order Sinc";
 
 } // namespace
@@ -798,8 +800,9 @@ START_API_FUNC
 {
     const char *ResamplerNames[] = {
         alPointResampler, alLinearResampler,
-        alCubicResampler, alBSinc12Resampler,
-        alBSinc24Resampler,
+        alCubicResampler, alFastBSinc12Resampler,
+        alBSinc12Resampler, alFastBSinc24Resampler,
+        alBSinc24Resampler
     };
     static_assert(al::size(ResamplerNames) == static_cast<ALuint>(Resampler::Max)+1,
         "Incorrect ResamplerNames list");

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);
 

alc/alu.h

@@ -46,7 +46,9 @@ enum class Resampler {
     Point,
     Linear,
     Cubic,
+    FastBSinc12,
     BSinc12,
+    FastBSinc24,
     BSinc24,
 
     Max = BSinc24

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);
     }

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()};

alsoftrc.sample

@@ -161,14 +161,18 @@
 #cf_level = 0
 
 ## resampler: (global)
-#  Selects the resampler used when mixing sources. Valid values are:
+#  Selects the default resampler used when mixing sources. Valid values are:
 #  point - nearest sample, no interpolation
 #  linear - extrapolates samples using a linear slope between samples
 #  cubic - extrapolates samples using a Catmull-Rom spline
 #  bsinc12 - extrapolates samples using a band-limited Sinc filter (varying
 #            between 12 and 24 points, with anti-aliasing)
+#  fast_bsinc12 - same as bsinc12, except without interpolation between down-
+#                 sampling scales
 #  bsinc24 - extrapolates samples using a band-limited Sinc filter (varying
 #            between 24 and 48 points, with anti-aliasing)
+#  fast_bsinc24 - same as bsinc24, except without interpolation between down-
+#                 sampling scales
 #resampler = linear
 
 ## rt-prio: (global)

utils/alsoft-config/mainwindow.cpp

@@ -101,7 +101,9 @@ static const struct NameValuePair {
     { "Linear", "linear" },
     { "Default (Linear)", "" },
     { "Cubic Spline", "cubic" },
+    { "11th order Sinc (fast)", "fast_bsinc12" },
     { "11th order Sinc", "bsinc12" },
+    { "23rd order Sinc (fast)", "fast_bsinc24" },
     { "23rd order Sinc", "bsinc24" },
 
     { "", "" }