Move ALEQFilter to alFilter.c/h and rename it to ALfilterState

2 files changed, 121 insertions, 0 deletions

diff --git a/OpenAL32/Include/alFilter.h b/OpenAL32/Include/alFilter.h
index 94feb3ee..f70b839e 100644
--- a/OpenAL32/Include/alFilter.h
+++ b/OpenAL32/Include/alFilter.h
@@ -46,6 +46,49 @@ static __inline ALfloat lpFilter2PC(const FILTER *iir, ALfloat input)
 ALfloat lpCoeffCalc(ALfloat g, ALfloat cw);
 
 
+typedef enum ALfilterType {
+    ALfilterType_HighShelf,
+    ALfilterType_LowShelf,
+    ALfilterType_Peaking,
+} ALfilterType;
+
+typedef struct ALfilterState {
+    ALfloat x[2]; /* History of two last input samples  */
+    ALfloat y[2]; /* History of two last output samples */
+    ALfloat a[3]; /* Transfer function coefficients "a" */
+    ALfloat b[3]; /* Transfer function coefficients "b" */
+} ALfilterState;
+
+void ALfilterState_clear(ALfilterState *filter);
+void ALfilterState_setParams(ALfilterState *filter, ALfilterType type, ALfloat gain, ALfloat freq_scale, ALfloat bandwidth);
+
+static __inline ALfloat ALfilterState_processSingle(ALfilterState *filter, ALfloat sample)
+{
+    ALfloat outsmp;
+
+    outsmp = filter->b[0] * sample +
+             filter->b[1] * filter->x[0] +
+             filter->b[2] * filter->x[1] -
+             filter->a[1] * filter->y[0] -
+             filter->a[2] * filter->y[1];
+    filter->x[1] = filter->x[0];
+    filter->x[0] = sample;
+    filter->y[1] = filter->y[0];
+    filter->y[0] = outsmp;
+
+    return outsmp;
+}
+
+static __inline ALfloat ALfilterState_processSingleC(const ALfilterState *filter, ALfloat sample)
+{
+    return filter->b[0] * sample +
+           filter->b[1] * filter->x[0] +
+           filter->b[2] * filter->x[1] -
+           filter->a[1] * filter->y[0] -
+           filter->a[2] * filter->y[1];
+}
+
+
 typedef struct ALfilter {
     // Filter type (AL_FILTER_NULL, ...)
     ALenum type;
diff --git a/OpenAL32/alFilter.c b/OpenAL32/alFilter.c
index 312cf681..6b4ce633 100644
--- a/OpenAL32/alFilter.c
+++ b/OpenAL32/alFilter.c
@@ -325,6 +325,84 @@ AL_API ALvoid AL_APIENTRY alGetFilterfv(ALuint filter, ALenum param, ALfloat *va
 }
 
 
+void ALfilterState_clear(ALfilterState *filter)
+{
+    filter->x[0] = 0.0f;
+    filter->x[1] = 0.0f;
+    filter->y[0] = 0.0f;
+    filter->y[1] = 0.0f;
+}
+
+void ALfilterState_setParams(ALfilterState *filter, ALfilterType type, ALfloat gain, ALfloat freq_scale, ALfloat bandwidth)
+{
+    ALfloat alpha;
+    ALfloat w0;
+
+    w0 = 2.0f*F_PI * freq_scale;
+
+    /* Calculate filter coefficients depending on filter type */
+    switch(type)
+    {
+        case ALfilterType_HighShelf:
+            alpha = sinf(w0) / 2.0f * sqrtf((gain + 1.0f/gain) *
+                                            (1.0f/0.75f - 1.0f) + 2.0f);
+            filter->b[0] = gain * ((gain + 1.0f) +
+                                   (gain - 1.0f) * cosf(w0) +
+                                   2.0f * sqrtf(gain) * alpha);
+            filter->b[1] = -2.0f * gain * ((gain - 1.0f) +
+                                           (gain + 1.0f) * cosf(w0));
+            filter->b[2] = gain * ((gain + 1.0f) +
+                                   (gain - 1.0f) * cosf(w0) -
+                                   2.0f * sqrtf(gain) * alpha);
+            filter->a[0] = (gain + 1.0f) -
+                           (gain - 1.0f) * cosf(w0) +
+                           2.0f * sqrtf(gain) * alpha;
+            filter->a[1] = 2.0f * ((gain - 1.0f) -
+                           (gain + 1.0f) * cosf(w0));
+            filter->a[2] = (gain + 1.0f) -
+                           (gain - 1.0f) * cosf(w0) -
+                           2.0f * sqrtf(gain) * alpha;
+            break;
+        case ALfilterType_LowShelf:
+            alpha = sinf(w0) / 2.0f * sqrtf((gain + 1.0f / gain) *
+                                            (1.0f / 0.75f - 1.0f) + 2.0f);
+            filter->b[0] = gain * ((gain + 1.0f) -
+                                   (gain - 1.0f) * cosf(w0) +
+                                   2.0f * sqrtf(gain) * alpha);
+            filter->b[1] = 2.0f * gain * ((gain - 1.0f) -
+                                          (gain + 1.0f) * cosf(w0));
+            filter->b[2] = gain * ((gain + 1.0f) -
+                                   (gain - 1.0f) * cosf(w0) -
+                                   2.0f * sqrtf(gain) * alpha);
+            filter->a[0] = (gain + 1.0f) +
+                           (gain - 1.0f) * cosf(w0) +
+                           2.0f * sqrtf(gain) * alpha;
+            filter->a[1] = -2.0f * ((gain - 1.0f) +
+                           (gain + 1.0f) * cosf(w0));
+            filter->a[2] = (gain + 1.0f) +
+                           (gain - 1.0f) * cosf(w0) -
+                           2.0f * sqrtf(gain) * alpha;
+            break;
+        case ALfilterType_Peaking:
+            alpha = sinf(w0) * sinhf(logf(2.0f) / 2.0f * bandwidth * w0 / sinf(w0));
+            filter->b[0] =  1.0f + alpha * gain;
+            filter->b[1] = -2.0f * cosf(w0);
+            filter->b[2] =  1.0f - alpha * gain;
+            filter->a[0] =  1.0f + alpha / gain;
+            filter->a[1] = -2.0f * cosf(w0);
+            filter->a[2] =  1.0f - alpha / gain;
+            break;
+    }
+
+    filter->b[0] /= filter->a[0];
+    filter->b[1] /= filter->a[0];
+    filter->b[2] /= filter->a[0];
+    filter->a[0] /= filter->a[0];
+    filter->a[1] /= filter->a[0];
+    filter->a[2] /= filter->a[0];
+}
+
+
 ALfloat lpCoeffCalc(ALfloat g, ALfloat cw)
 {
     ALfloat a = 0.0f;