Implement AL_EFFECT_REVERB

 Here is a quick description of how the reverb effect works:

 +--->---+*(4)
 |       V       new sample
 +-----+---+---+    |
 |extra|ltr|ref| <- +*(1)
 +-----+---+---+
   (3,5)*|   |*(2)
         +-->|
             V
         out sample

 1) Apply master reverb gain to incoming sample and place it at the head of the
    buffer. The master reverb gainhf was already applied when the source was
    initially mixed.
 2) Copy the delayed reflection sample to an output sample and apply the
    reflection gain.
 3) Apply the late reverb gain to the late reverb sample
 4) Copy the end of the buffer, applying a decay gain and the decay hf ratio,
    and add to the late reverb.
 5) Copy the late reverb sample, adding to the output sample.

 Then the head and sampling points are shifted forward, and done again for each
 new sample. The extra buffer length is determined by the Reverb Density
 property. A value of 0 gives a length of 0.1 seconds (long, with fairly
 distinct echos) , and 1 gives 0.075 seconds (short, indistinct echos).
 The decay gain is calculated such that after a number of loops to satisfy the
 Decay Time, a sample will be 1/32768th as powerful (virtually insignificant to
 the resulting output, and only getting further reduced). It is calculated as:

 DecayGain = pow(1.0f/32768.0f, 1.0/(DecayTime/ExtraLength));

 Things to note: Reverb Diffusion is not currently handled, nor is Decay HF
 Limit. Decay HF Ratios above 1 probably give incorrect results. Also, this
 method likely sucks, but it's the best I can come up with before release. :)

3 files changed, 165 insertions, 26 deletions

diff --git a/Alc/ALu.c b/Alc/ALu.c
index d7bd5aa0..c6df899c 100644
--- a/Alc/ALu.c
+++ b/Alc/ALu.c
@@ -311,6 +311,12 @@ static ALvoid CalcSourceParams(ALCcontext *ALContext, ALsource *ALSource,
         //2. Calculate distance attenuation
         Distance = aluSqrt(aluDotproduct(Position, Position));
 
+        if(ALSource->Send[0].Slot && !ALSource->Send[0].Slot->AuxSendAuto)
+        {
+            if(ALSource->Send[0].Slot->effect.type == AL_EFFECT_REVERB)
+                RoomRolloff = ALSource->Send[0].Slot->effect.Reverb.RoomRolloffFactor;
+        }
+
         flAttenuation = 1.0f;
         RoomAttenuation = 1.0f;
         switch (ALContext->DistanceModel)
@@ -371,14 +377,11 @@ static ALvoid CalcSourceParams(ALCcontext *ALContext, ALsource *ALSource,
         DryMix = SourceVolume * flAttenuation;
         DryMix = __min(DryMix,MaxVolume);
         DryMix = __max(DryMix,MinVolume);
-        if(ALSource->Send[0].Slot)
-        {
-            WetMix = SourceVolume * ((ALSource->WetGainAuto &&
-                                      ALSource->Send[0].Slot->AuxSendAuto) ?
-                                     RoomAttenuation : 1.0f);
-            WetMix = __min(WetMix,MaxVolume);
-            WetMix = __max(WetMix,MinVolume);
-        }
+
+        WetMix = SourceVolume * (ALSource->WetGainAuto ?
+                                 RoomAttenuation : 1.0f);
+        WetMix = __min(WetMix,MaxVolume);
+        WetMix = __max(WetMix,MinVolume);
 
         //3. Apply directional soundcones
         SourceToListener[0] = -Position[0];
@@ -473,6 +476,18 @@ static ALvoid CalcSourceParams(ALCcontext *ALContext, ALsource *ALSource,
             DryGainHF *= pow(ALSource->AirAbsorptionFactor * AIRABSORBGAINHF,
                              Distance * MetersPerUnit);
 
+        if(ALSource->Send[0].Slot)
+        {
+            WetMix *= ALSource->Send[0].Slot->Gain;
+
+            if(ALSource->Send[0].Slot->effect.type == AL_EFFECT_REVERB)
+            {
+                WetGainHF *= ALSource->Send[0].Slot->effect.Reverb.GainHF;
+                WetGainHF *= pow(ALSource->Send[0].Slot->effect.Reverb.AirAbsorptionGainHF,
+                                 Distance * MetersPerUnit);
+            }
+        }
+
         //7. Convert normalized position into pannings, then into channel volumes
         aluNormalize(Position);
         switch(aluChannelsFromFormat(OutputFormat))
@@ -482,7 +497,6 @@ static ALvoid CalcSourceParams(ALCcontext *ALContext, ALsource *ALSource,
                 drysend[FRONT_RIGHT] = ConeVolume * ListenerGain * DryMix * aluSqrt(1.0f); //Direct
                 if(ALSource->Send[0].Slot)
                 {
-                    WetMix *= ALSource->Send[0].Slot->Gain;
                     wetsend[FRONT_LEFT]  = ListenerGain * WetMix * aluSqrt(1.0f); //Room
                     wetsend[FRONT_RIGHT] = ListenerGain * WetMix * aluSqrt(1.0f); //Room
                 }
@@ -499,7 +513,6 @@ static ALvoid CalcSourceParams(ALCcontext *ALContext, ALsource *ALSource,
                 drysend[FRONT_RIGHT] = ConeVolume * ListenerGain * DryMix * aluSqrt(     PanningLR); //R Direct
                 if(ALSource->Send[0].Slot)
                 {
-                    WetMix *= ALSource->Send[0].Slot->Gain;
                     wetsend[FRONT_LEFT]  = ListenerGain * WetMix * aluSqrt(1.0f-PanningLR); //L Room
                     wetsend[FRONT_RIGHT] = ListenerGain * WetMix * aluSqrt(     PanningLR); //R Room
                 }
@@ -526,7 +539,6 @@ static ALvoid CalcSourceParams(ALCcontext *ALContext, ALsource *ALSource,
                 drysend[BACK_RIGHT]  = ConeVolume * ListenerGain * DryMix * aluSqrt((     PanningLR)*(     PanningFB));
                 if(ALSource->Send[0].Slot)
                 {
-                    WetMix *= ALSource->Send[0].Slot->Gain;
                     wetsend[FRONT_LEFT]  = ListenerGain * WetMix * aluSqrt((1.0f-PanningLR)*(1.0f-PanningFB));
                     wetsend[FRONT_RIGHT] = ListenerGain * WetMix * aluSqrt((     PanningLR)*(1.0f-PanningFB));
                     wetsend[BACK_LEFT]   = ListenerGain * WetMix * aluSqrt((1.0f-PanningLR)*(     PanningFB));
@@ -559,7 +571,6 @@ static ALvoid CalcSourceParams(ALCcontext *ALContext, ALsource *ALSource,
                     drysend[FRONT_RIGHT] = 0.0f;
                     if(ALSource->Send[0].Slot)
                     {
-                        WetMix *= ALSource->Send[0].Slot->Gain;
                         wetsend[BACK_LEFT]   = ListenerGain * WetMix * aluSqrt((1.0f-PanningLR)*(1.0f-PanningFB));
                         wetsend[BACK_RIGHT]  = ListenerGain * WetMix * aluSqrt((     PanningLR)*(1.0f-PanningFB));
                         wetsend[SIDE_LEFT]   = ListenerGain * WetMix * aluSqrt((1.0f-PanningLR)*(     PanningFB));
@@ -588,7 +599,6 @@ static ALvoid CalcSourceParams(ALCcontext *ALContext, ALsource *ALSource,
                     drysend[BACK_RIGHT]  = 0.0f;
                     if(ALSource->Send[0].Slot)
                     {
-                        WetMix *= ALSource->Send[0].Slot->Gain;
                         wetsend[FRONT_LEFT]  = ListenerGain * WetMix * aluSqrt((1.0f-PanningLR)*(1.0f-PanningFB));
                         wetsend[FRONT_RIGHT] = ListenerGain * WetMix * aluSqrt((     PanningLR)*(1.0f-PanningFB));
                         wetsend[SIDE_LEFT]   = ListenerGain * WetMix * aluSqrt((1.0f-PanningLR)*(     PanningFB));
@@ -660,6 +670,7 @@ ALvoid aluMixData(ALCcontext *ALContext,ALvoid *buffer,ALsizei size,ALenum forma
 {
     static float DryBuffer[BUFFERSIZE][OUTPUTCHANNELS];
     static float WetBuffer[BUFFERSIZE][OUTPUTCHANNELS];
+    static float ReverbBuffer[BUFFERSIZE];
     ALfloat DrySend[OUTPUTCHANNELS] = { 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f };
     ALfloat WetSend[OUTPUTCHANNELS] = { 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f };
     ALfloat DryGainHF = 0.0f;
@@ -667,12 +678,14 @@ ALvoid aluMixData(ALCcontext *ALContext,ALvoid *buffer,ALsizei size,ALenum forma
     ALuint BlockAlign,BufferSize;
     ALuint DataSize=0,DataPosInt=0,DataPosFrac=0;
     ALuint Channels,Frequency,ulExtraSamples;
+    ALboolean doReverb;
     ALfloat Pitch;
     ALint Looping,increment,State;
     ALuint Buffer,fraction;
     ALuint SamplesToDo;
     ALsource *ALSource;
     ALbuffer *ALBuffer;
+    ALeffectslot *ALEffectSlot;
     ALfloat value;
     ALshort *Data;
     ALuint i,j,k;
@@ -698,12 +711,18 @@ ALvoid aluMixData(ALCcontext *ALContext,ALvoid *buffer,ALsizei size,ALenum forma
             //Clear mixing buffer
             memset(DryBuffer, 0, SamplesToDo*OUTPUTCHANNELS*sizeof(ALfloat));
             memset(WetBuffer, 0, SamplesToDo*OUTPUTCHANNELS*sizeof(ALfloat));
+            memset(ReverbBuffer, 0, SamplesToDo*sizeof(ALfloat));
 
             //Actual mixing loop
             while(ALSource)
             {
                 j = 0;
                 State = ALSource->state;
+
+                doReverb = ((ALSource->Send[0].Slot &&
+                             ALSource->Send[0].Slot->effect.type == AL_EFFECT_REVERB) ?
+                            AL_TRUE : AL_FALSE);
+
                 while(State == AL_PLAYING && j < SamplesToDo)
                 {
                     DataSize = 0;
@@ -798,12 +817,17 @@ ALvoid aluMixData(ALCcontext *ALContext,ALvoid *buffer,ALsizei size,ALenum forma
                                 DryBuffer[j][BACK_RIGHT]  += value*DrySend[BACK_RIGHT];
                                 //Room path final mix buffer and panning
                                 value = aluComputeWetSample(ALSource, WetGainHF, sample);
-                                WetBuffer[j][FRONT_LEFT]  += value*WetSend[FRONT_LEFT];
-                                WetBuffer[j][FRONT_RIGHT] += value*WetSend[FRONT_RIGHT];
-                                WetBuffer[j][SIDE_LEFT]   += value*WetSend[SIDE_LEFT];
-                                WetBuffer[j][SIDE_RIGHT]  += value*WetSend[SIDE_RIGHT];
-                                WetBuffer[j][BACK_LEFT]   += value*WetSend[BACK_LEFT];
-                                WetBuffer[j][BACK_RIGHT]  += value*WetSend[BACK_RIGHT];
+                                if(doReverb)
+                                    ReverbBuffer[j] += value;
+                                else
+                                {
+                                    WetBuffer[j][FRONT_LEFT]  += value*WetSend[FRONT_LEFT];
+                                    WetBuffer[j][FRONT_RIGHT] += value*WetSend[FRONT_RIGHT];
+                                    WetBuffer[j][SIDE_LEFT]   += value*WetSend[SIDE_LEFT];
+                                    WetBuffer[j][SIDE_RIGHT]  += value*WetSend[SIDE_RIGHT];
+                                    WetBuffer[j][BACK_LEFT]   += value*WetSend[BACK_LEFT];
+                                    WetBuffer[j][BACK_RIGHT]  += value*WetSend[BACK_RIGHT];
+                                }
                             }
                             else
                             {
@@ -945,6 +969,61 @@ ALvoid aluMixData(ALCcontext *ALContext,ALvoid *buffer,ALsizei size,ALenum forma
                 ALSource = ALSource->next;
             }
 
+            ALEffectSlot = (ALContext ? ALContext->AuxiliaryEffectSlot : NULL);
+            while(ALEffectSlot)
+            {
+                if(ALEffectSlot->effect.type == AL_EFFECT_REVERB)
+                {
+                    ALfloat *DelayBuffer = ALEffectSlot->ReverbBuffer;
+                    ALuint Pos = ALEffectSlot->ReverbPos;
+                    ALuint LatePos = ALEffectSlot->ReverbLatePos;
+                    ALuint ReflectPos = ALEffectSlot->ReverbReflectPos;
+                    ALuint Length = ALEffectSlot->ReverbLength;
+                    ALfloat DecayGain = ALEffectSlot->ReverbDecayGain;
+                    ALfloat DecayHFRatio = ALEffectSlot->effect.Reverb.DecayHFRatio;
+                    ALfloat Gain = ALEffectSlot->effect.Reverb.Gain;
+                    ALfloat ReflectGain = ALEffectSlot->effect.Reverb.ReflectionsGain;
+                    ALfloat LateReverbGain = ALEffectSlot->effect.Reverb.LateReverbGain;
+                    ALfloat LastDecaySample = ALEffectSlot->LastDecaySample;
+                    ALfloat sample;
+
+                    for(i = 0;i < SamplesToDo;i++)
+                    {
+                        DelayBuffer[Pos] = ReverbBuffer[i] * Gain;
+
+                        sample = DelayBuffer[ReflectPos] * ReflectGain;
+
+                        DelayBuffer[LatePos] *= LateReverbGain;
+
+                        Pos = (Pos+1) % Length;
+                        DelayBuffer[Pos] *= DecayHFRatio;
+                        DelayBuffer[Pos] += LastDecaySample * (1.0f-DecayHFRatio);
+                        LastDecaySample = DelayBuffer[Pos];
+                        DelayBuffer[Pos] *= DecayGain;
+
+                        DelayBuffer[LatePos] += DelayBuffer[Pos];
+
+                        sample += DelayBuffer[LatePos];
+
+                        WetBuffer[i][FRONT_LEFT]  += sample;
+                        WetBuffer[i][FRONT_RIGHT] += sample;
+                        WetBuffer[i][SIDE_LEFT]   += sample;
+                        WetBuffer[i][SIDE_RIGHT]  += sample;
+                        WetBuffer[i][BACK_LEFT]   += sample;
+                        WetBuffer[i][BACK_RIGHT]  += sample;
+
+                        LatePos = (LatePos+1) % Length;
+                        ReflectPos = (ReflectPos+1) % Length;
+                    }
+
+                    ALEffectSlot->ReverbPos = Pos;
+                    ALEffectSlot->ReverbLatePos = LatePos;
+                    ALEffectSlot->ReverbReflectPos = ReflectPos;
+                    ALEffectSlot->LastDecaySample = LastDecaySample;
+                }
+                ALEffectSlot = ALEffectSlot->next;
+            }
+
             //Post processing loop
             switch(format)
             {
diff --git a/OpenAL32/Include/alAuxEffectSlot.h b/OpenAL32/Include/alAuxEffectSlot.h
index 66b3ba20..d4cb0d11 100644
--- a/OpenAL32/Include/alAuxEffectSlot.h
+++ b/OpenAL32/Include/alAuxEffectSlot.h
@@ -21,6 +21,15 @@ typedef struct ALeffectslot
     ALfloat Gain;
     ALboolean AuxSendAuto;
 
+    ALfloat *ReverbBuffer;
+    // in frames!
+    ALuint ReverbLength;
+    ALuint ReverbPos;
+    ALuint ReverbReflectPos;
+    ALuint ReverbLatePos;
+    ALfloat ReverbDecayGain;
+    ALfloat LastDecaySample;
+
     ALuint refcount;
 
     // Index to itself
diff --git a/OpenAL32/alAuxEffectSlot.c b/OpenAL32/alAuxEffectSlot.c
index 3ce845ce..41ea6c72 100644
--- a/OpenAL32/alAuxEffectSlot.c
+++ b/OpenAL32/alAuxEffectSlot.c
@@ -21,6 +21,7 @@
 #include "config.h"
 
 #include <stdlib.h>
+#include <math.h>
 
 #include "AL/al.h"
 #include "AL/alc.h"
@@ -30,6 +31,9 @@
 #include "alError.h"
 
 
+static ALvoid InitializeEffect(ALCcontext *Context, ALeffectslot *ALEffectSlot, ALeffect *effect);
+
+
 AL_API ALvoid AL_APIENTRY alGenAuxiliaryEffectSlots(ALsizei n, ALuint *effectslots)
 {
     ALCcontext *Context;
@@ -144,6 +148,8 @@ AL_API ALvoid AL_APIENTRY alDeleteAuxiliaryEffectSlots(ALsizei n, ALuint *effect
                         *list = (*list)->next;
                     ALTHUNK_REMOVEENTRY(ALAuxiliaryEffectSlot->effectslot);
 
+                    free(ALAuxiliaryEffectSlot->ReverbBuffer);
+
                     memset(ALAuxiliaryEffectSlot, 0, sizeof(ALeffectslot));
                     free(ALAuxiliaryEffectSlot);
 
@@ -202,13 +208,7 @@ AL_API ALvoid AL_APIENTRY alAuxiliaryEffectSloti(ALuint effectslot, ALenum param
             if(alIsEffect(iValue))
             {
                 ALeffect *effect = (ALeffect*)ALTHUNK_LOOKUPENTRY(iValue);
-                if(!effect)
-                {
-                    ALEffectSlot->effect.type = AL_EFFECT_NULL;
-                    ALEffectSlot->effect.effect = 0;
-                }
-                else
-                    memcpy(&ALEffectSlot->effect, effect, sizeof(*effect));
+                InitializeEffect(Context, ALEffectSlot, effect);
             }
             else
                 alSetError(AL_INVALID_VALUE);
@@ -465,6 +465,55 @@ AL_API ALvoid AL_APIENTRY alGetAuxiliaryEffectSlotfv(ALuint effectslot, ALenum p
 }
 
 
+static ALvoid InitializeEffect(ALCcontext *Context, ALeffectslot *ALEffectSlot, ALeffect *effect)
+{
+    ALfloat *ptr = NULL;
+
+    if(!effect)
+    {
+        memset(&ALEffectSlot->effect, 0, sizeof(ALEffectSlot->effect));
+        goto done;
+    }
+
+    if(effect->type == AL_EFFECT_REVERB)
+    {
+        ALuint size;
+        ALfloat reverbwait;
+
+        reverbwait = (1.0f-effect->Reverb.Density)*(0.1f-0.075f) + 0.075f;
+
+        size = (ALuint)((ALfloat)Context->Frequency *
+                        (effect->Reverb.ReflectionsDelay +
+                         effect->Reverb.LateReverbDelay +
+                         reverbwait)) + 1;
+
+        ptr = calloc(size, sizeof(ALfloat));
+        if(!ptr)
+        {
+            alSetError(AL_OUT_OF_MEMORY);
+            return;
+        }
+        ALEffectSlot->ReverbLength = size;
+        ALEffectSlot->ReverbPos = 0;
+        ALEffectSlot->ReverbReflectPos = (ALuint)(ALEffectSlot->ReverbLength -
+                                          ((ALfloat)Context->Frequency *
+                                           effect->Reverb.ReflectionsDelay)) %
+                                         ALEffectSlot->ReverbLength;
+        ALEffectSlot->ReverbLatePos = (ALuint)(ALEffectSlot->ReverbLength -
+                                               ((ALfloat)Context->Frequency *
+                                              (effect->Reverb.LateReverbDelay +
+                                           effect->Reverb.ReflectionsDelay))) %
+                                         ALEffectSlot->ReverbLength;
+        ALEffectSlot->ReverbDecayGain = pow(1.0/32768.0, 1.0/(effect->Reverb.DecayTime/reverbwait));
+    }
+
+    memcpy(&ALEffectSlot->effect, effect, sizeof(*effect));
+done:
+    free(ALEffectSlot->ReverbBuffer);
+    ALEffectSlot->ReverbBuffer = ptr;
+}
+
+
 ALvoid ReleaseALAuxiliaryEffectSlots(ALCcontext *Context)
 {
 #ifdef _DEBUG
@@ -478,6 +527,8 @@ ALvoid ReleaseALAuxiliaryEffectSlots(ALCcontext *Context)
         Context->AuxiliaryEffectSlot = Context->AuxiliaryEffectSlot->next;
 
         // Release effectslot structure
+        free(temp->ReverbBuffer);
+
         memset(temp, 0, sizeof(ALeffectslot));
         free(temp);
     }