Add some preliminary fields for mix-time ambisonic upsampling

OpenAL32/Include/alu.h

@@ -20,6 +20,7 @@
 #include "logging.h"
 #include "math_defs.h"
 #include "filters/biquad.h"
+#include "filters/splitter.h"
 #include "filters/nfc.h"
 #include "almalloc.h"
 #include "alnumeric.h"
@@ -204,10 +205,11 @@ struct ALvoiceProps : public ALvoicePropsBase {
     DEF_NEWDEL(ALvoiceProps)
 };
 
-#define VOICE_IS_STATIC (1<<0)
-#define VOICE_IS_FADING (1<<1) /* Fading sources use gain stepping for smooth transitions. */
-#define VOICE_HAS_HRTF  (1<<2)
-#define VOICE_HAS_NFC   (1<<3)
+#define VOICE_IS_STATIC    (1u<<0)
+#define VOICE_IS_FADING    (1u<<1) /* Fading sources use gain stepping for smooth transitions. */
+#define VOICE_IS_AMBISONIC (1u<<2) /* Voice needs HF scaling for ambisonic upsampling. */
+#define VOICE_HAS_HRTF     (1u<<3)
+#define VOICE_HAS_NFC      (1u<<4)
 
 struct ALvoice {
     std::atomic<ALvoiceProps*> Update{nullptr};
@@ -253,6 +255,9 @@ struct ALvoice {
 
     InterpState ResampleState;
 
+    std::array<ALfloat,MAX_AMBI_ORDER+1> AmbiScales;
+    BandSplitter AmbiSplitter[MAX_INPUT_CHANNELS];
+
     struct {
         int FilterType;
         DirectParams Params[MAX_INPUT_CHANNELS];

OpenAL32/alSource.cpp

@@ -41,6 +41,7 @@
 #include "alFilter.h"
 #include "alAuxEffectSlot.h"
 #include "ringbuffer.h"
+#include "bformatdec.h"
 
 #include "backends/base.h"
 
@@ -2828,6 +2829,19 @@ AL_API ALvoid AL_APIENTRY alSourcePlayv(ALsizei n, const ALuint *sources)
         voice->Flags = start_fading ? VOICE_IS_FADING : 0;
         if(source->SourceType == AL_STATIC) voice->Flags |= VOICE_IS_STATIC;
 
+        /* Don't need to set the VOICE_IS_AMBISONIC flag if the device is
+         * mixing in first order. No HF scaling is necessary to mix it.
+         */
+        if(((*buffer)->mFmtChannels == FmtBFormat2D || (*buffer)->mFmtChannels == FmtBFormat3D) &&
+           device->mAmbiOrder > 1)
+        {
+            voice->AmbiScales = AmbiUpsampler::GetHFOrderScales(1, device->mAmbiOrder);
+            voice->AmbiSplitter[0].init(400.0f / static_cast<ALfloat>(device->Frequency));
+            for(ALsizei i{1};i < voice->NumChannels;++i)
+                voice->AmbiSplitter[i] = voice->AmbiSplitter[0];
+            voice->Flags |= VOICE_IS_AMBISONIC;
+        }
+
         std::fill_n(std::begin(voice->Direct.Params), voice->NumChannels, DirectParams{});
         std::for_each(voice->Send.begin(), voice->Send.end(),
             [voice](ALvoice::SendData &send) -> void