From 7a7a4844f441a2d269cffdadfd553655a8d3484e Mon Sep 17 00:00:00 2001
From: Chris Robinson <chris.kcat@gmail.com>
Date: Thu, 16 Apr 2009 05:43:09 -0700
Subject: [PATCH] Make the filter history buffer size flexible This lets the
 filter history buffer be as big as needed for a given use, so that it can
 have a size large enough for the more demanding cases, but not be wasteful
 for lesser-demanding cases, while not incuring the overhead of an added
 pointer indirection

---
 Alc/ALu.c                   | 12 ++++++------
 Alc/alcEcho.c               |  6 ++++--
 OpenAL32/Include/alFilter.h |  2 +-
 OpenAL32/Include/alSource.h |  2 ++
 4 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/Alc/ALu.c b/Alc/ALu.c
index a8371367..1d1878af 100644
--- a/Alc/ALu.c
+++ b/Alc/ALu.c
@@ -181,9 +181,9 @@ __inline ALuint aluChannelsFromFormat(ALenum format)
 }
 
 
-static __inline ALfloat lpFilter4P(FILTER *iir, ALfloat input)
+static __inline ALfloat lpFilter4P(FILTER *iir, ALuint offset, ALfloat input)
 {
-    ALfloat *history = iir->history;
+    ALfloat *history = &iir->history[offset];
     ALfloat a = iir->coeff;
     ALfloat output = input;
 
@@ -199,9 +199,9 @@ static __inline ALfloat lpFilter4P(FILTER *iir, ALfloat input)
     return output;
 }
 
-static __inline ALfloat lpFilter2P(FILTER *iir, ALuint chan, ALfloat input)
+static __inline ALfloat lpFilter2P(FILTER *iir, ALuint offset, ALfloat input)
 {
-    ALfloat *history = &iir->history[chan*2];
+    ALfloat *history = &iir->history[offset];
     ALfloat a = iir->coeff;
     ALfloat output = input;
 
@@ -1179,7 +1179,7 @@ ALvoid aluMixData(ALCcontext *ALContext,ALvoid *buffer,ALsizei size,ALenum forma
                             value = lerp(Data[k], Data[k+1], DataPosFrac);
 
                             //Direct path final mix buffer and panning
-                            outsamp = lpFilter4P(DryFilter, value);
+                            outsamp = lpFilter4P(DryFilter, 0, value);
                             DryBuffer[j][FRONT_LEFT]   += outsamp*DrySend[FRONT_LEFT];
                             DryBuffer[j][FRONT_RIGHT]  += outsamp*DrySend[FRONT_RIGHT];
                             DryBuffer[j][SIDE_LEFT]    += outsamp*DrySend[SIDE_LEFT];
@@ -1219,7 +1219,7 @@ ALvoid aluMixData(ALCcontext *ALContext,ALvoid *buffer,ALsizei size,ALenum forma
         for(i = 0;i < Channels;i++) \
         { \
             value = lerp(Data[k*Channels + i], Data[(k+1)*Channels + i], DataPosFrac); \
-            values[i] = lpFilter2P(DryFilter, chans[i], value)*DrySend[chans[i]]; \
+            values[i] = lpFilter2P(DryFilter, chans[i]*2, value)*DrySend[chans[i]]; \
         } \
         for(out = 0;out < OUTPUTCHANNELS;out++) \
         { \
diff --git a/Alc/alcEcho.c b/Alc/alcEcho.c
index cbc57a03..f6606bfa 100644
--- a/Alc/alcEcho.c
+++ b/Alc/alcEcho.c
@@ -48,7 +48,9 @@ struct ALechoState {
     ALfloat GainR;
 
     ALfloat FeedGain;
+
     FILTER iirFilter;
+    ALfloat history[2];
 };
 
 // Find the next power of 2.  Actually, this will return the input value if
@@ -100,8 +102,8 @@ ALechoState *EchoCreate(ALCcontext *Context)
     state->GainL = 0.0f;
     state->GainR = 0.0f;
 
-    for(i = 0;i < sizeof(state->iirFilter.history)/sizeof(state->iirFilter.history[0]);i++)
-        state->iirFilter.history[i] = 0.0f;
+    for(i = 0;i < sizeof(state->history)/sizeof(state->history[0]);i++)
+        state->history[i] = 0.0f;
     state->iirFilter.coeff = 0.0f;
 
     return state;
diff --git a/OpenAL32/Include/alFilter.h b/OpenAL32/Include/alFilter.h
index 413f2a12..40fff4fd 100644
--- a/OpenAL32/Include/alFilter.h
+++ b/OpenAL32/Include/alFilter.h
@@ -9,8 +9,8 @@ extern "C" {
 #endif
 
 typedef struct {
-    ALfloat history[OUTPUTCHANNELS*2];
     ALfloat coeff;
+    ALfloat history[0];
 } FILTER;
 
 #define AL_FILTER_TYPE                                     0x8001
diff --git a/OpenAL32/Include/alSource.h b/OpenAL32/Include/alSource.h
index 28a85029..2bd7aac2 100644
--- a/OpenAL32/Include/alSource.h
+++ b/OpenAL32/Include/alSource.h
@@ -69,6 +69,7 @@ typedef struct ALsource
         struct ALeffectslot *Slot;
         ALfilter WetFilter;
         FILTER iirFilter;
+        ALfloat history[2];
     } Send[MAX_SENDS];
 
     ALboolean DryGainHFAuto;
@@ -77,6 +78,7 @@ typedef struct ALsource
     ALfloat   OuterGainHF;
 
     FILTER iirFilter;
+    ALfloat history[OUTPUTCHANNELS*2];
 
     ALfloat AirAbsorptionFactor;
 
-- 
2.11.4.GIT