Move the bnad-splitter filters to a separate source

2 files changed, 147 insertions, 0 deletions

diff --git a/Alc/filters/splitter.c b/Alc/filters/splitter.c
new file mode 100644
index 00000000..524bcc1d
--- /dev/null
+++ b/Alc/filters/splitter.c
@@ -0,0 +1,107 @@
+
+#include "config.h"
+
+#include "splitter.h"
+
+#include "math_defs.h"
+
+
+void bandsplit_init(BandSplitter *splitter, ALfloat f0norm)
+{
+    ALfloat w = f0norm * F_TAU;
+    ALfloat cw = cosf(w);
+    if(cw > FLT_EPSILON)
+        splitter->coeff = (sinf(w) - 1.0f) / cw;
+    else
+        splitter->coeff = cw * -0.5f;
+
+    splitter->lp_z1 = 0.0f;
+    splitter->lp_z2 = 0.0f;
+    splitter->hp_z1 = 0.0f;
+}
+
+void bandsplit_clear(BandSplitter *splitter)
+{
+    splitter->lp_z1 = 0.0f;
+    splitter->lp_z2 = 0.0f;
+    splitter->hp_z1 = 0.0f;
+}
+
+void bandsplit_process(BandSplitter *splitter, ALfloat *restrict hpout, ALfloat *restrict lpout,
+                       const ALfloat *input, ALsizei count)
+{
+    ALfloat lp_coeff, hp_coeff, lp_y, hp_y, d;
+    ALfloat lp_z1, lp_z2, hp_z1;
+    ALsizei i;
+
+    hp_coeff = splitter->coeff;
+    lp_coeff = splitter->coeff*0.5f + 0.5f;
+    lp_z1 = splitter->lp_z1;
+    lp_z2 = splitter->lp_z2;
+    hp_z1 = splitter->hp_z1;
+    for(i = 0;i < count;i++)
+    {
+        ALfloat in = input[i];
+
+        /* Low-pass sample processing. */
+        d = (in - lp_z1) * lp_coeff;
+        lp_y = lp_z1 + d;
+        lp_z1 = lp_y + d;
+
+        d = (lp_y - lp_z2) * lp_coeff;
+        lp_y = lp_z2 + d;
+        lp_z2 = lp_y + d;
+
+        lpout[i] = lp_y;
+
+        /* All-pass sample processing. */
+        d = in - hp_coeff*hp_z1;
+        hp_y = hp_z1 + hp_coeff*d;
+        hp_z1 = d;
+
+        /* High-pass generated from removing low-passed output. */
+        hpout[i] = hp_y - lp_y;
+    }
+    splitter->lp_z1 = lp_z1;
+    splitter->lp_z2 = lp_z2;
+    splitter->hp_z1 = hp_z1;
+}
+
+
+void splitterap_init(SplitterAllpass *splitter, ALfloat f0norm)
+{
+    ALfloat w = f0norm * F_TAU;
+    ALfloat cw = cosf(w);
+    if(cw > FLT_EPSILON)
+        splitter->coeff = (sinf(w) - 1.0f) / cw;
+    else
+        splitter->coeff = cw * -0.5f;
+
+    splitter->z1 = 0.0f;
+}
+
+void splitterap_clear(SplitterAllpass *splitter)
+{
+    splitter->z1 = 0.0f;
+}
+
+void splitterap_process(SplitterAllpass *splitter, ALfloat *restrict samples, ALsizei count)
+{
+    ALfloat coeff, d, x;
+    ALfloat z1;
+    ALsizei i;
+
+    coeff = splitter->coeff;
+    z1 = splitter->z1;
+    for(i = 0;i < count;i++)
+    {
+        x = samples[i];
+
+        d = x - coeff*z1;
+        x = z1 + coeff*d;
+        z1 = d;
+
+        samples[i] = x;
+    }
+    splitter->z1 = z1;
+}
diff --git a/Alc/filters/splitter.h b/Alc/filters/splitter.h
new file mode 100644
index 00000000..a788bc3e
--- /dev/null
+++ b/Alc/filters/splitter.h
@@ -0,0 +1,40 @@
+#ifndef FILTER_SPLITTER_H
+#define FILTER_SPLITTER_H
+
+#include "alMain.h"
+
+
+/* Band splitter. Splits a signal into two phase-matching frequency bands. */
+typedef struct BandSplitter {
+    ALfloat coeff;
+    ALfloat lp_z1;
+    ALfloat lp_z2;
+    ALfloat hp_z1;
+} BandSplitter;
+
+void bandsplit_init(BandSplitter *splitter, ALfloat f0norm);
+void bandsplit_clear(BandSplitter *splitter);
+void bandsplit_process(BandSplitter *splitter, ALfloat *restrict hpout, ALfloat *restrict lpout,
+                       const ALfloat *input, ALsizei count);
+
+/* The all-pass portion of the band splitter. Applies the same phase shift
+ * without splitting the signal.
+ */
+typedef struct SplitterAllpass {
+    ALfloat coeff;
+    ALfloat z1;
+} SplitterAllpass;
+
+void splitterap_init(SplitterAllpass *splitter, ALfloat f0norm);
+void splitterap_clear(SplitterAllpass *splitter);
+void splitterap_process(SplitterAllpass *splitter, ALfloat *restrict samples, ALsizei count);
+
+
+typedef struct FrontStablizer {
+    SplitterAllpass APFilter[MAX_OUTPUT_CHANNELS];
+    BandSplitter LFilter, RFilter;
+    alignas(16) ALfloat LSplit[2][BUFFERSIZE];
+    alignas(16) ALfloat RSplit[2][BUFFERSIZE];
+} FrontStablizer;
+
+#endif /* FILTER_SPLITTER_H */