Add a compile-time macro to use dual-band ambisonic HRTF processing

Use single-band processing for now, to see if dual-band is causing a drop in
quality at all.

1 files changed, 36 insertions, 12 deletions

diff --git a/Alc/hrtf.c b/Alc/hrtf.c
index b11fb9a8..d0511083 100644
--- a/Alc/hrtf.c
+++ b/Alc/hrtf.c
@@ -198,6 +198,11 @@ ALuint BuildBFormatHrtf(const struct Hrtf *Hrtf, ALfloat (*coeffs)[HRIR_LENGTH][
         { { 0.25f,  0.14425f, -0.14425f, -0.14425f }, { 0.125f,  0.125f, -0.125f, -0.125f } },
         { { 0.25f, -0.14425f, -0.14425f, -0.14425f }, { 0.125f, -0.125f, -0.125f, -0.125f } },
     };
+/* Change this to 2 for dual-band HRTF processing. May require a higher quality
+ * band-splitter, or better calculation of the new IR length to deal with the
+ * tail generated by the filter.
+ */
+#define NUM_BANDS 1
     BandSplitter splitter;
     ALfloat temps[3][HRIR_LENGTH];
     ALuint lidx[8], ridx[8];
@@ -239,18 +244,27 @@ ALuint BuildBFormatHrtf(const struct Hrtf *Hrtf, ALfloat (*coeffs)[HRIR_LENGTH][
         const ALshort *fir;
         ALuint delay;
 
-        /* Band-split left HRIR into low and high frequency responses. */
-        bandsplit_clear(&splitter);
+        /* Convert the left FIR from shorts to float */
         fir = &Hrtf->coeffs[lidx[c] * Hrtf->irSize];
-        for(i = 0;i < Hrtf->irSize;i++)
-            temps[2][i] = fir[i] / 32767.0f;
-        bandsplit_process(&splitter, temps[0], temps[1], temps[2], HRIR_LENGTH);
+        if(NUM_BANDS == 1)
+        {
+            for(i = 0;i < Hrtf->irSize;i++)
+                temps[0][i] = fir[i] / 32767.0f;
+        }
+        else
+        {
+            /* Band-split left HRIR into low and high frequency responses. */
+            bandsplit_clear(&splitter);
+            for(i = 0;i < Hrtf->irSize;i++)
+                temps[2][i] = fir[i] / 32767.0f;
+            bandsplit_process(&splitter, temps[0], temps[1], temps[2], HRIR_LENGTH);
+        }
 
         /* Add to the left output coefficients with the specified delay. */
         delay = Hrtf->delays[lidx[c]] - min_delay;
         for(i = 0;i < NumChannels;++i)
         {
-            for(b = 0;b < 2;b++)
+            for(b = 0;b < NUM_BANDS;b++)
             {
                 ALuint k = 0;
                 for(j = delay;j < HRIR_LENGTH;++j)
@@ -259,18 +273,27 @@ ALuint BuildBFormatHrtf(const struct Hrtf *Hrtf, ALfloat (*coeffs)[HRIR_LENGTH][
         }
         max_length = maxu(max_length, minu(delay + Hrtf->irSize, HRIR_LENGTH));
 
-        /* Band-split right HRIR into low and high frequency responses. */
-        bandsplit_clear(&splitter);
+        /* Convert the right FIR from shorts to float */
         fir = &Hrtf->coeffs[ridx[c] * Hrtf->irSize];
-        for(i = 0;i < Hrtf->irSize;i++)
-            temps[2][i] = fir[i] / 32767.0f;
-        bandsplit_process(&splitter, temps[0], temps[1], temps[2], HRIR_LENGTH);
+        if(NUM_BANDS == 1)
+        {
+            for(i = 0;i < Hrtf->irSize;i++)
+                temps[0][i] = fir[i] / 32767.0f;
+        }
+        else
+        {
+            /* Band-split right HRIR into low and high frequency responses. */
+            bandsplit_clear(&splitter);
+            for(i = 0;i < Hrtf->irSize;i++)
+                temps[2][i] = fir[i] / 32767.0f;
+            bandsplit_process(&splitter, temps[0], temps[1], temps[2], HRIR_LENGTH);
+        }
 
         /* Add to the right output coefficients with the specified delay. */
         delay = Hrtf->delays[ridx[c]] - min_delay;
         for(i = 0;i < NumChannels;++i)
         {
-            for(b = 0;b < 2;b++)
+            for(b = 0;b < NUM_BANDS;b++)
             {
                 ALuint k = 0;
                 for(j = delay;j < HRIR_LENGTH;++j)
@@ -280,6 +303,7 @@ ALuint BuildBFormatHrtf(const struct Hrtf *Hrtf, ALfloat (*coeffs)[HRIR_LENGTH][
         max_length = maxu(max_length, minu(delay + Hrtf->irSize, HRIR_LENGTH));
     }
     TRACE("Skipped min delay: %u, new combined length: %u\n", min_delay, max_length);
+#undef NUM_BANDS
 
     return max_length;
 }