From feeec3433377d46f71771c3930e5e00bf9834feb Mon Sep 17 00:00:00 2001
From: Chris Robinson <chris.kcat@gmail.com>
Date: Mon, 27 May 2013 19:14:02 -0700
Subject: Use ALfilterState for the source direct and send filters

---
 OpenAL32/Include/alFilter.h |  2 ++
 OpenAL32/Include/alSource.h |  6 ++----
 OpenAL32/alFilter.c         | 11 +++++++++++
 3 files changed, 15 insertions(+), 4 deletions(-)

(limited to 'OpenAL32')

diff --git a/OpenAL32/Include/alFilter.h b/OpenAL32/Include/alFilter.h
index f70b839e..9273f15c 100644
--- a/OpenAL32/Include/alFilter.h
+++ b/OpenAL32/Include/alFilter.h
@@ -47,6 +47,8 @@ ALfloat lpCoeffCalc(ALfloat g, ALfloat cw);
 
 
 typedef enum ALfilterType {
+    ALfilterType_LowPass,
+
     ALfilterType_HighShelf,
     ALfilterType_LowShelf,
     ALfilterType_Peaking,
diff --git a/OpenAL32/Include/alSource.h b/OpenAL32/Include/alSource.h
index bd1b2931..8766c85e 100644
--- a/OpenAL32/Include/alSource.h
+++ b/OpenAL32/Include/alSource.h
@@ -61,8 +61,7 @@ typedef struct DirectParams {
      * target (eg. FrontLeft). Not used with HRTF. */
     ALfloat Gains[MaxChannels][MaxChannels];
 
-    /* A low-pass filter, using 2 chained one-pole filters. */
-    FILTER Filter[MaxChannels];
+    ALfilterState Filter[MaxChannels];
 } DirectParams;
 
 typedef struct SendParams {
@@ -72,8 +71,7 @@ typedef struct SendParams {
      * output buffer. */
     ALfloat Gain;
 
-    /* A low-pass filter, using 2 chained one-pole filters. */
-    FILTER Filter[MaxChannels];
+    ALfilterState Filter[MaxChannels];
 } SendParams;
 
 
diff --git a/OpenAL32/alFilter.c b/OpenAL32/alFilter.c
index 5bef87fd..550c99f5 100644
--- a/OpenAL32/alFilter.c
+++ b/OpenAL32/alFilter.c
@@ -343,6 +343,17 @@ void ALfilterState_setParams(ALfilterState *filter, ALfilterType type, ALfloat g
     /* Calculate filter coefficients depending on filter type */
     switch(type)
     {
+        case ALfilterType_LowPass:
+            alpha = sinf(w0) / 2.0f * sqrtf((gain + 1.0f/gain) *
+                                            (1.0f/0.75f - 1.0f) + 2.0f);
+            filter->b[0] = (1.0f - cosf(w0)) * 0.5f;
+            filter->b[1] =  1.0f - cosf(w0);
+            filter->b[2] = (1.0f - cosf(w0)) * 0.5f;
+            filter->a[0] =  1.0f + alpha;
+            filter->a[1] = -2.0f*cosf(w0);
+            filter->a[2] =  1.0f - alpha;
+            break;
+
         case ALfilterType_HighShelf:
             alpha = sinf(w0) / 2.0f * sqrtf((gain + 1.0f/gain) *
                                             (1.0f/0.75f - 1.0f) + 2.0f);
-- 
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