Mix to multichannel for effects

This mixes to a 4-channel first-order ambisonics buffer. With ACN ordering and
N3D scaling, this makes it easy to remain compatible with effects that only
care about mono input since channel 0 is an unattenuated mono signal.

2 files changed, 23 insertions, 6 deletions

diff --git a/OpenAL32/Include/alAuxEffectSlot.h b/OpenAL32/Include/alAuxEffectSlot.h
index bbb112be..3f677fd1 100644
--- a/OpenAL32/Include/alAuxEffectSlot.h
+++ b/OpenAL32/Include/alAuxEffectSlot.h
@@ -64,6 +64,9 @@ static const struct ALeffectStateFactoryVtable T##_ALeffectStateFactory_vtable =
 }
 
 
+#define MAX_EFFECT_CHANNELS (4)
+
+
 typedef struct ALeffectslot {
     ALenum EffectType;
     ALeffectProps EffectProps;
@@ -74,12 +77,24 @@ typedef struct ALeffectslot {
     ATOMIC(ALenum) NeedsUpdate;
     ALeffectState *EffectState;
 
-    alignas(16) ALfloat WetBuffer[1][BUFFERSIZE];
-
     RefCount ref;
 
     /* Self ID */
     ALuint id;
+
+    ALuint NumChannels;
+    ChannelConfig AmbiCoeffs[MAX_EFFECT_CHANNELS];
+    /* Wet buffer configuration is ACN channel order with N3D scaling:
+     * * Channel 0 is the unattenuated mono signal.
+     * * Channel 1 is OpenAL -X
+     * * Channel 2 is OpenAL Y
+     * * Channel 3 is OpenAL -Z
+     * Consequently, effects that only want to work with mono input can use
+     * channel 0 by itself. Effects that want multichannel can process the
+     * ambisonics signal and create a B-Format pan (ComputeBFormatGains) for
+     * the device output.
+     */
+    alignas(16) ALfloat WetBuffer[MAX_EFFECT_CHANNELS][BUFFERSIZE];
 } ALeffectslot;
 
 inline struct ALeffectslot *LookupEffectSlot(ALCcontext *context, ALuint id)
diff --git a/OpenAL32/Include/alu.h b/OpenAL32/Include/alu.h
index 5f5493c5..63a03adc 100644
--- a/OpenAL32/Include/alu.h
+++ b/OpenAL32/Include/alu.h
@@ -13,6 +13,7 @@
 #include "alMain.h"
 #include "alBuffer.h"
 #include "alFilter.h"
+#include "alAuxEffectSlot.h"
 
 #include "hrtf.h"
 #include "align.h"
@@ -34,6 +35,7 @@ extern "C" {
 
 struct ALsource;
 struct ALvoice;
+struct ALeffectslot;
 
 
 /* The number of distinct scale and phase intervals within the filter table. */
@@ -164,6 +166,7 @@ typedef struct DirectParams {
 
 typedef struct SendParams {
     ALfloat (*OutBuffer)[BUFFERSIZE];
+    ALuint OutChannels;
 
     ALboolean Moving;
     ALuint Counter;
@@ -173,10 +176,7 @@ typedef struct SendParams {
         ALfilterState LowPass;
         ALfilterState HighPass;
     } Filters[MAX_INPUT_CHANNELS];
-
-    /* Gain control, which applies to each input channel to a single (mono)
-     * output buffer. */
-    MixGains Gains[MAX_INPUT_CHANNELS];
+    MixGains Gains[MAX_INPUT_CHANNELS][MAX_EFFECT_CHANNELS];
 } SendParams;
 
 
@@ -276,6 +276,8 @@ void aluInitMixer(void);
 
 ALvoid aluInitPanning(ALCdevice *Device);
 
+void aluInitEffectPanning(struct ALeffectslot *slot);
+
 /**
  * CalcDirectionCoeffs
  *